Endre søk
Begrens søket
1234567 101 - 150 of 343
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 101.
    Fernandes, Carla Patricia Duarte
    et al.
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre for Mental Disorders Research (NORMENT), Department of Clinical Science, University of Bergen, Dr. Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway.
    Westlye, Lars Tjelta
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre For Mental Disorders Research (NORMENT), Division of Mental Health and Addiction, Oslo University Hospital & Institute of Clinical Medicine, Department of Psychology, University of Oslo, Oslo N-0317, Norway.
    Giddaluru, Sudheer
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre for Mental Disorders Research (NORMENT), Department of Clinical Science, University of Bergen, Dr. Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway.
    Christoforou, Andrea
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre for Mental Disorders Research (NORMENT), Department of Clinical Science, University of Bergen, Dr. Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway.
    Kauppi, Karolina
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Adolfsson, Rolf
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Psykiatri.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University and Stockholm Brain Institute, Uppsala, Sweden.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Lundervold, Astri Johansen
    Department of Biological and Medical Psychology, K.G. Jebsen Centre for Research on Neuropsychiatric Disorders, University of Bergen, Bergen, Norway, Kavli Research Centre for Aging and Dementia, Haraldsplass Deaconess Hospital.
    Reinvang, Ivar
    Department of Psychology, University of Oslo, Oslo N-0317, Norway.
    Steen, Vidar Martin
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre for Mental Disorders Research (NORMENT), Department of Clinical Science, University of Bergen, Dr. Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway.
    Le Hellard, Stéphanie
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre for Mental Disorders Research (NORMENT), Department of Clinical Science, University of Bergen, Dr. Einar Martens Research Group for Biological Psychiatry, Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway.
    Espeseth, Thomas
    K.G. Jebsen Centre for Psychosis Research, Norwegian Centre For Mental Disorders Research (NORMENT), Division of Mental Health and Addiction, Oslo University Hospital & Institute of Clinical Medicine, Department of Psychology, University of Oslo, Oslo N-0317, Norway.
    Lack of association of the rs1344706 ZNF804A variant with cognitive functions and DTI indices of white matter microstructure in two independent healthy populations2014Inngår i: Psychiatry Research: Neuroimaging, ISSN 0925-4927, E-ISSN 1872-7506, Vol. 222, nr 1-2, s. 60-66Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The rs1344706 single nucleotide polymorphism within intron 2 of the ZNF804A gene is strongly associated with schizophrenia and bipolar disorder. This variant has also been associated in some studies with a range of cognitive and neuroimaging phenotypes, but several studies have reported no effect on the same phenotypes in other samples. Here, we genotyped 670 healthy adult Norwegian subjects and 1753 healthy adult Swedish subjects for rs1344706, and tested for associations with cognitive phenotypes including general intellectual abilities, memory functions and cognitive inhibition. We also tested whether rs1344706 is associated with white matter microstructural properties using diffusion tensor imaging (DTI) data from 250 to 340 of the Norwegian and Swedish subjects, respectively. Whole-brain voxel-wise statistical modeling of the effect of the ZNF804A variant on two DTI indices, fractional anisotropy (FA) and radial diffusivity (RD), was performed using tract-based spatial statistics (TBSS), and commonly reported effect sizes were calculated within several large-scale white matter pathways based on neuroanatomical atlases. No significant associations were found between rs1344706 and the cognitive traits or white matter microstructure. We conclude that the rs1344706 SNP has no significant effect on these phenotypes in our two reasonably powered samples.

  • 102.
    Fischer, Håkan
    et al.
    Karolinska Institute.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Bäckman, Lars
    Karolinska Institute.
    Age-related differences in brain regions supporting successful encoding of emotional faces.2010Inngår i: Cortex, ISSN 0010-9452, E-ISSN 1973-8102, Vol. 46, nr 4, s. 490-497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In an event-related functional Magnetic Resonance Imaging (fMRI) study, younger and older adults were presented with negative emotional (i.e., fearful) and neutral face pictures under incidental learning conditions. They were subsequently given a test of face recognition outside the scanner. Both age groups activated amygdala bilaterally as well as the right hippocampus during successful encoding of the fearful faces. Direct age comparisons revealed greater activation in right amygdala and bilateral hippocampus in the young, whereas older adults showed greater activation in the left insular and right prefrontal cortices. None of these brain areas was activated during successful encoding of neutral faces, suggesting specificity of these brain activation patterns. The results indicate an age-related shift in the neural underpinnings of negative emotional face processing from medial-temporal to neocortical regions.

  • 103. Flanagan, J R
    et al.
    King, S
    Wolpert, D M
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Sensorimotor prediction and memory in object manipulation2001Inngår i: Canadian journal of experimental psychology, ISSN 1196-1961, E-ISSN 1878-7290, Vol. 55, nr 2, s. 87-95Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When people lift objects of different size but equal weight, they initially employ too much force for the large object and too little force for the small object. However, over repeated lifts of the two objects, they learn to suppress the size-weight association used to estimate force requirements and appropriately scale their lifting forces to the true and equal weights of the objects. Thus, sensorimotor memory from previous lifts comes to dominate visual size information in terms of force prediction. Here we ask whether this sensorimotor memory is transient, preserved only long enough to perform the task, or more stable. After completing an initial lift series in which they lifted equally weighted large and small objects in alternation, participants then repeated the lift series after delays of 15 minutes or 24 hours. In both cases, participants retained information about the weights of the objects and used this information to predict the appropriate fingertip forces. This preserved sensorimotor memory suggests that participants acquired internal models of the size-weight stimuli that could be used for later prediction.

  • 104. Flanagan, J Randall
    et al.
    Bittner, Jennifer P
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Experience can change distinct size-weight priors engaged in lifting objects and judging their weights.2008Inngår i: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 18, nr 22, s. 1742-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The expectation that object weight increases with size guides the control of manipulatory actions [1-6] and also influences weight perception. Thus, the size-weight illusion, whereby people perceive the smaller of two equally weighted objects to be heavier, is thought to arise because weight is judged relative to expected weight that, for a given family of objects, increases with size [2, 7]. Here, we show that the fundamental expectation that weight increases with size can be altered by experience and neither is hard-wired nor becomes crystallized during development. We demonstrate that multiday practice in lifting a set of blocks whose color and texture are the same and whose weights vary inversely with volume gradually attenuates and ultimately inverts the size-weight illusion tested with similar blocks. We also show that in contrast to this gradual change in the size-weight illusion, the sensorimotor system rapidly learns to predict the inverted object weights, as revealed by lift forces. Thus, our results indicate that distinct adaptive size-weight maps, or priors, underlie weight predictions made in lifting objects and in judging their weights. We suggest that size-weight priors that influence weight perception change slowly because they are based on entire families of objects. Size-weight priors supporting action are more flexible, and adapt more rapidly, because they are tuned to specific objects and their current state.

  • 105. Flanagan, J Randall
    et al.
    Bowman, Miles C
    Johansson, Roland
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Control strategies in object manipulation tasks.2006Inngår i: Current Opinion in Neurobiology, ISSN 0959-4388, Vol. 16, nr 6, s. 650-9Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The remarkable manipulative skill of the human hand is not the result of rapid sensorimotor processes, nor of fast or powerful effector mechanisms. Rather, the secret lies in the way manual tasks are organized and controlled by the nervous system. At the heart of this organization is prediction. Successful manipulation requires the ability both to predict the motor commands required to grasp, lift, and move objects and to predict the sensory events that arise as a consequence of these commands.

  • 106.
    Flanagan, J Randall
    et al.
    Queen's University, Kingston, Ontario K7L 3N6.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Action plans used in action observation2003Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, ISSN 1476-4687, Vol. 424, nr 6950, s. 769-771Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    How do we understand the actions of others? According to the direct matching hypothesis, action understanding results from a mechanism that maps an observed action onto motor representations of that action. Although supported by neurophysiological and brain-imaging studies, direct evidence for this hypothesis is sparse. In visually guided actions, task-specific proactive eye movements are crucial for planning and control. Because the eyes are free to move when observing such actions, the direct matching hypothesis predicts that subjects should produce eye movements similar to those produced when they perform the tasks. If an observer analyses action through purely visual means, however, eye movements will be linked reactively to the observed action. Here we show that when subjects observe a block stacking task, the coordination between their gaze and the actor's hand is predictive, rather than reactive, and is highly similar to the gaze-hand coordination when they perform the task themselves. These results indicate that during action observation subjects implement eye motor programs directed by motor representations of manual actions and thus provide strong evidence for the direct matching hypothesis.

  • 107.
    Flanagan, J Randall
    et al.
    Department of Psychology and Centre for Neuroscience Studies, Queen’s University, Kingston, Ontario, Canada.
    Merritt, Kyle
    Department of Psychology and Centre for Neuroscience Studies, Queen’s University, Kingston, Ontario, Canada.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Predictive mechanisms and object representations used in object manipulation2009Inngår i: Sensorimotor Control of Grasping: Physiology and Pathophysiology, Cambridge: Cambridge University Press , 2009, s. 161-177Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Skilled object manipulation requires the ability to estimate, in advance, the motor commands needed to achieve desired sensory outcomes and the ability to predict the sensory consequences of the motor commands. Because the mapping between motor commands and sensory outcomes depends on the physical properties of grasped objects, the motor system may store and access internal models of objects in order to estimate motor commands and predict sensory consequences. In this chapter, we outline evidence for internal models and discuss their role in object manipulation tasks. We also consider the relationship between internal models of objects employedby the sensorimotor system and representations of the same objects used by the perceptual system to make judgments about objects.

  • 108.
    Flanagan, J Randall
    et al.
    Department of Psychology, Queen's University, Kingston, Ontario, Canada, Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Rotman, Gerben
    Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Reichelt, Andreas F
    Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    The role of observers' gaze behaviour when watching object manipulation tasks: predicting and evaluating the consequences of action2013Inngår i: Philosophical Transactions of the Royal Society of London. Biological Sciences, ISSN 0962-8436, E-ISSN 1471-2970, Vol. 368, nr 1628, s. 20130063-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When watching an actor manipulate objects, observers, like the actor, naturally direct their gaze to each object as the hand approaches and typically maintain gaze on the object until the hand departs. Here, we probed the function of observers' eye movements, focusing on two possibilities: (i) that observers' gaze behaviour arises from processes involved in the prediction of the target object of the actor's reaching movement and (ii) that this gaze behaviour supports the evaluation of mechanical events that arise from interactions between the actor's hand and objects. Observers watched an actor reach for and lift one of two presented objects. The observers' task was either to predict the target object or judge its weight. Proactive gaze behaviour, similar to that seen in self-guided action-observation, was seen in the weight judgement task, which requires evaluating mechanical events associated with lifting, but not in the target prediction task. We submit that an important function of gaze behaviour in self-guided action observation is the evaluation of mechanical events associated with interactions between the hand and object. By comparing predicted and actual mechanical events, observers, like actors, can gain knowledge about the world, including information about objects they may subsequently act upon.

  • 109. Flanagan, J Randall
    et al.
    Terao, Yasuo
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Gaze behavior when reaching to remembered targets.2008Inngår i: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 100, nr 3, s. 1533-43Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    People naturally direct their gaze to visible hand movement goals. Doing so improves reach accuracy through use of signals related to gaze position and visual feedback of the hand. Here, we studied where people naturally look when acting on remembered target locations. Four targets were presented on a screen, in peripheral vision, while participants fixed a central cross (encoding phase). Four seconds later, participants used a pen to mark the remembered locations while free to look wherever they wished (recall phase). Visual references, including the screen and the cross, were present throughout. During recall, participants neither looked at the marked locations nor prevented eye movements. Instead, gaze behavior was erratic and was comprised of gaze shifts loosely coupled in time and space with hand movements. To examine whether eye and hand movements during encoding affected gaze behavior during recall, in additional encoding conditions, participants marked the visible targets with either free gaze or with central cross fixation or just looked at the targets. All encoding conditions yielded similar erratic gaze behavior during recall. Furthermore, encoding mode did not influence recall performance, suggesting that participants, during recall, did not exploit sensorimotor memories related to hand and gaze movements during encoding. Finally, we recorded a similar lose coupling between hand and eye movements during an object manipulation task performed in darkness after participants had viewed the task environment. We conclude that acting on remembered versus visible targets can engage fundamentally different control strategies, with gaze largely decoupled from movement goals during memory-guided actions.

  • 110.
    Flanagan, J Randall
    et al.
    Queen's University, Kingston, Ontario.
    Vetter, Philipp
    University College London, Queen Square, London.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Wolpert, Daniel M
    University College London, Queen Square, London.
    Prediction precedes control in motor learning2003Inngår i: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 13, nr 2, s. 146-150, Article Number: PII S0960-9822(03)00007-1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Skilled motor behavior relies on the brain learning both to control the body and predict the consequences of this control. Prediction turns motor commands into expected sensory consequences, whereas control turns desired consequences into motor commands. To capture this symmetry, the neural processes underlying prediction and control are termed the forward and inverse internal models, respectively. Here, we investigate how these two fundamental processes are related during motor learning. We used an object manipulation task in which subjects learned to move a hand-held object with novel dynamic properties along a prescribed path. We independently and simultaneously measured subjects' ability to control their actions and to predict their consequences. We found different time courses for predictor and controller learning, with prediction being learned far more rapidly than control. In early stages of manipulating the object, subjects could predict the consequences of their actions, as measured by the grip force they used to grasp the object, but could not generate appropriate actions for control, as measured by their hand trajectory. As predicted by several recent theoretical models of sensorimotor control, our results indicate that people can learn to predict the consequences of their actions before they can learn to control their actions.

  • 111.
    Fytagoridis, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap, Klinisk neurovetenskap.
    Sjöberg, Richard
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap, Klinisk neurovetenskap.
    Åström, Mattias
    Fredricks, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap, Klinisk neurovetenskap.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Blomstedt, Patric
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap, Klinisk neurovetenskap.
    Effects of deep brain stimulation in the caudal Zona incerta on verbal fluency2013Inngår i: Stereotactic and Functional Neurosurgery, ISSN 1011-6125, E-ISSN 1423-0372, Vol. 91, nr 1, s. 24-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background: Deep brain stimulation (DBS) of the caudal zona incerta (cZi) is a relatively unexplored and promising treatment in patients with severe essential tremor (ET). Preliminary data further indicate that the ability to produce language may be slightly affected by the treatment.

    Objective: To evaluate the effects on verbal fluency following cZi DBS in patients with ET.

    Method: Seventeen consecutive patients who had undergone DBS of the cZi for ET were tested regarding verbal fluency before surgery, 3 days after surgery and after 1 year. Ten patients were also evaluated by comparing performance on versus off stimulation after 1 year.

    Results: The total verbal fluency score decreased slightly, but significantly, from 22.7 (SD = 10.9) before surgery to 18.1 (SD = 7.5) 3 days after surgery (p = 0.036). After 1 year the score was nonsignificantly decreased to 20.1 (SD = 9.7, p = 0.2678). There was no detectable difference between stimulation on and off after 1 year.

    Conclusion: There was a tendency of an immediate and mostly transient postoperative decline in verbal fluency following cZi DBS for ET. In some of the patients this reduction was, however, more pronounced and also sustained over time.

  • 112.
    Grigoriadis, Anastasios
    et al.
    Karolinska Institutet.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Trulsson, Mats
    Karolinska Institutet.
    Adaptability of mastication in people with implant-supported bridges2011Inngår i: Journal of Clinical Periodontology, ISSN 0303-6979, E-ISSN 1600-051X, Vol. 38, nr 4, s. 395-404Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Objectives: We aimed to determine whether people with implant-supported bridges in both jaws, thus lacking periodontal receptors, adjust jaw muscle activity to food hardness during mastication.

    Materials and Methods: Thirteen participants with implant-supported bridges in both jaws and 13 with natural dentition chewed and swallowed soft and hard gelatine-based model foods, while electromyographic (EMG) activity of the masseter and temporal muscles was recorded bilaterally together with the position of the mandible. Data were compared by using a mixed-design anova model and a P-value<0.05 was considered statistically significant.

    Results: The number of chewing cycles and the duration of the masticatory sequence increased with food hardness in both groups, whereas vertical and lateral amplitude of the jaw movements, and the jaw-opening velocity, increased significantly with food hardness only for the dentate group. Although both groups adapted the EMG activity to the hardness of the food, the implant participants showed a significantly weaker increase in EMG activity with increased food hardness early during the masticatory sequence than the dentate participants did. In addition, the implant group showed significantly less reduction of muscle activity during the progression of the masticatory sequence than the dentate group.

    Conclusions: People with implant-supported bridges show an impaired adaptation of the muscle activity to food hardness during mastication. We suggest that a lack of sensory signals from periodontal mechanoreceptors accounts for the impairment.

  • 113.
    Gustafsson, Dan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    A model for investigating microcircuit changes underlying functional recovery after brain lesion in vivo2016Independent thesis Advanced level (degree of Master (Two Years)), 30 poäng / 45 hpOppgave
  • 114.
    Gåfvels, Mats
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Blood flow and metabolism in the corpus luteum of the rat: in vivo and in vitro studies on the ovarian luteal and follicular compartment of the rat1987Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The ovary undergoes cyclic changes in follicular growth and luteogenesis due to the action of gonadotropins and steroids. The ovary and especially the corpus luteum has an exteremely high blood flow. There is a gap in our knowledge about the physiological role of the high blood flow of the corpus luteum.

    The production of lactate, progesterone and cyclic AMP of follicles and corpora lutea incubated in vitro was analyzed and related to the tissue content of ATP to elucidate possible connections between oxygen and substrate levels and energy consumption, steroid output and LH responsiveness in vitro. It was also considered of interest to investigate if the oxygen tensions needed for ATP and progesterone production of the follicle and the corpus luteum differed. A corpus luteum model using adult pseudopregnant rats was developed and characterized according to criteria for identification of corpora lutea as well as levels of plasma steroids and gonadotropins. In vitro progesterone production was compared to plasma progesterone levels. The absolute blood flow of corpora lutea of different ages and the response to injection of hCG, noradrenaline and antidiuretic hormone was investigated with the microsphere technique. Relative blood flow changes of follicles and corpora lutea during follicular growth and luteogenesis in vivo were studied by injecting radiolabelled microspheres to anaesthetized immature rats at different time periods after injection of an ovulatory dose of pregnant mare serum gonadotropin. This approach was chosen to investigate the possible relation between follicular/luteal blood flow, steroid output and morphology in relation to the endogenous gonadotropin surge, ovulation and luteogenesis.

    Hormonal stimulation by injection of hCG and noradrenaline increased total ovarian blood flow but no evidence was found for a parallelism between luteotropism and blood flow. The increasing effect of hCG on ovarian blood flow was partly due to a shunting of blood from the uterus towards the ovary. The antidiuretic hormone potently decreased ovarian and uterine blood flow by 80-90% while blood flow of some other organs (e.g. kidney and spleen) were hardly affected. The corpus luteum of pseudopregnancy was found to produce 15“ 20 times more progesterone in vitro as compared to the preovulatory follicle. The steroidogenesis and energy production of corpora lutea was found to be more sensitive to decreases in oxygen tension in terms of tissue ATP levels and LH responsiveness of progesterone production while the follicle could compensate by increasing glycolysis. A parallelism between follicular/luteal blood flow and progesterone production in vivo was found. It was shown that the formation, growth and progesterone production of the corpus luteum was accompanied by an increase in blood flow as well as vascularization as seen under the light microscope. The endogenous gonadotropin surge did not change follicular blood flow due to the development of a follicular oedema. We hypothesize that the corpus luteum function in vivo and in vitro is dependent on higher energy levels than the preovulatory follicle and that the transformation of the follicle to a corpus luteum is supported by a high nutritive blood flow possibly to support a high demand for energy-rich substrates.

  • 115.
    Haage, David
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Obstetrik och gynekologi.
    Bäckström, Torbjörn
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Obstetrik och gynekologi.
    Johansson, Staffan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Interaction between allopregnanolone and pregnenolone sulfate in modulating GABA-mediated synaptic currents in neurons from the rat medial preoptic nucleus.2005Inngår i: Brain Research, ISSN 0006-8993, Vol. 1033, nr 1, s. 58-67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The two neurosteroids 3alpha-hydroxy-5alpha-pregnane-20-one (allopregnanolone; AlloP) and pregnenolone sulfate (PregS) affect neuronal GABA(A) receptors differently. While AlloP mainly potentiates the currents through GABA(A) receptors, PregS reduces such currents. The present study aimed at clarifying the interaction of AlloP and PregS at GABA(A) receptors in neurons from the medial preoptic nucleus of male rat. AlloP has previously been shown to dramatically prolong GABA-mediated spontaneous inhibitory postsynaptic currents (sIPSCs) in these neurons. Here, by recording sIPSCs under voltage-clamp conditions with the perforated-patch technique, it was shown that PregS by itself did not significantly affect the amplitude or time course of such currents. However, PregS, in a concentration-dependent manner, reduced the AlloP-evoked prolongation of sIPSC decay when the two neurosteroids were applied together. In contrast to sIPSC amplitude and time course, sIPSC frequency was significantly reduced by 10 microM PregS alone. Further, although 1.0 microM AlloP alone induced a clear increase in sIPSC frequency, the frequency was not significantly different from control when 1.0 microM AlloP was applied in combination with 10 microM PregS. In addition to the effects on sIPSC parameters, PregS reduced the baseline current evoked by 1.0 microM AlloP in the absence of GABA application or synaptic activity. PregS by itself did not significantly affect the baseline current. The main effects of AlloP and PregS on the sIPSC time course were mimicked by a simplified model with AlloP assumed to reduce the rate of GABA unbinding from the receptor and PregS assumed to increase the rate of desensitization.

  • 116.
    Haage, David
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Druzin, Michael
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Laboratory of Ionic Channels of Cell Membranes, Institute of Cytology, Russian Academy of Sciences, Russia.
    Johansson, Staffan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Allopregnanolone modulates spontaneous GABA release via presynaptic Cl- permeability in rat preoptic nerve terminals2002Inngår i: Brain Research, ISSN 0006-8993, E-ISSN 1872-6240, Vol. 958, nr 2, s. 405-413Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The endogenous neurosteroid 3alpha-hydroxy-5alpha-pregnane-20-one (allopregnanolone) affects presynaptic nerve terminals and thereby increases the frequency of spontaneous GABA release. The present study aimed at clarifying the mechanisms underlying this presynaptic neurosteroid action, by recording the frequency of spontaneous GABA-mediated inhibitory postsynaptic currents (sIPSCs) in neurons from the medial preoptic nucleus (MPN) of rat. Acutely dissociated neurons with functional adhering nerve terminals were studied by perforated-patch recording under voltage-clamp conditions. It was shown that the sIPSC frequency increased with the external K(+) concentration ([K(+)](o)). Further, the effect of allopregnanolone on the sIPSC frequency was strongly dependent on [K(+)](o). In a [K(+)](o) of 5 mM, 2.0 microM allopregnanolone caused a clear increase in sIPSC frequency. However, the effect declined rapidly with increased [K(+)](o) and at high [K(+)](o) allopregnanolone reduced the sIPSC frequency. The effect of allopregnanolone was also strongly dependent on the external Cl(-) concentration ([Cl(-)](o)). In a reduced [Cl(-)](o) (40 mM, but with a standard [K(+)](o) of 5 mM), the effect on sIPSC frequency was larger than that in the standard [Cl(-)](o) of 146 mM. The dependence of the effect of allopregnanolone on [K(+)](o) and on estimated presynaptic membrane potential was also altered by the reduction in [Cl(-)](o). As in standard [Cl(-)](o), the effect in low [Cl(-)](o) declined when [K(+)](o) was raised, but reversed at a higher [K(+)](o). The GABA(A) receptor agonist muscimol also potentiated the sIPSC frequency. Altogether, the results suggest that allopregnanolone exerts its presynaptic effect by increasing the presynaptic Cl(-) permeability, most likely via GABA(A) receptors.

  • 117. Habib, Reza
    et al.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Neural Correlates of Availability and Accessibility in Memory2008Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 8, nr 7, s. 1720-1726Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Failure to remember can be due to not having information available in memory or to an inability to access information that is available. We used functional magnetic resonance imaging to examine brain responses during encoding and successive cued recall and associative recognition tests of paired associates. Items were classified into 3 categories based on performance on the 2 retrieval tests: 1) successfully remembered (both recalled and recognized), 2) inaccessible (not recalled but later recognized), and 3) forgotten (neither recalled nor recognized). During cued recall, availability in memory was signaled in a network of regions including bilateral medial temporal lobe, left middle temporal cortex, and the parietal cortex. Memory access resulted in heightened activity in these regions as well as in left inferior frontal cortex. Encoding-related activity in hippocampus and inferior temporal cortex predicted subsequent availability and left inferior frontal activity predicted subsequent access. These results suggest that failure to access information that is available in memory may reflect weaker memory representations.

  • 118.
    Hansson, C
    et al.
    Sahlgrenska Academy at the University of Gothenburg.
    Haage, D
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Sahlgrenska Academy at the University of Gothenburg.
    Taube, M
    Sahlgrenska Academy at the University of Gothenburg.
    Egecioglu, E
    Sahlgrenska Academy at the University of Gothenburg.
    Salomé, N
    Sahlgrenska Academy at the University of Gothenburg.
    Dickson, S L
    Sahlgrenska Academy at the University of Gothenburg.
    Central administration of ghrelin alters emotional responses in rats: behavioural, electrophysiological and molecular evidence2011Inngår i: Neuroscience, ISSN 0306-4522, E-ISSN 1873-7544, Vol. 180, s. 201-211Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The orexigenic and pro-obesity hormone ghrelin targets key hypothalamic and mesolimbic circuits involved in energy balance, appetite and reward. Given that such circuits are closely integrated with those regulating mood and cognition, we sought to determine whether chronic (>2 weeks) CNS exposure to ghrelin alters anxiety- and depression-like behaviour in rats as well as some physiological correlates. Rats bearing chronically implanted i.c.v. catheters were treated with ghrelin (10 μg/d) or vehicle for 4 weeks. Tests used to assess anxiety- and depression-like behaviour were undertaken during weeks 3-4 of the infusion. These revealed an increase in anxiety- and depression-like behaviour in the ghrelin-treated rats relative to controls. At the end of the 4-week infusion, brains were removed and the amygdala dissected for subsequent qPCR analysis that revealed changes in expression of a number of genes representing key systems implicated in these behavioural changes. Finally, given the key role of the dorsal raphe serotonin system in emotional reactivity, we examined the electrophysiological response of dorsal raphe neurons after a ghrelin challenge, and found mainly inhibitory responses in this region. We demonstrate that the central ghrelin signalling system is involved in emotional reactivity in rats, eliciting pro-anxiety and pro-depression effects and have begun to explore novel target systems for ghrelin that may be of importance for these effects.

  • 119.
    Hansson, Patrik
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Sunnegårdh-Grönberg, Karin
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi, Tandhygienistutbildning.
    Bergdahl, Jan
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Bergdahl, Maud
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Nilsson, Lars-Göran
    Relationship between natural teeth and memory in a healthy elderly population2013Inngår i: European Journal of Oral Sciences, ISSN 0909-8836, E-ISSN 1600-0722, Vol. 121, nr 4, s. 333-340Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The relationship between mastication and cognitive function remains unclear, but both animal and experimental human studies suggest a possible causal relationship. In the present study it was hypothesized that natural teeth are of importance for hippocampus-based cognitive processes, such as episodic long-term memory. A population-based sample of 273 participants (55-80yr of age; 145 women) was investigated in a cross-sectional study. The participants underwent health assessment, completed a battery of cognitive tests, and took part in an extensive clinical oral examination. The number of natural teeth contributed uniquely and significantly to explaining variance (3-4%) in performance on measures of episodic memory and semantic memory over and above individual differences in age, years of education, gender, occupation, living conditions, and medical history. The number of natural teeth did not have an influence on the performance of measures of working memory, visuospatial ability, or processing speed. Within the limitations of the current study, a small, but significant, relationship between episodic memory and number of natural teeth is evident.

  • 120.
    Hao, Manzhao
    et al.
    Institute of Rehabilitation Engineering, Med-X Research Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
    He, Xin
    Institute of Rehabilitation Engineering, Med-X Research Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
    Xiao, Qin
    Institute of Rehabilitation Engineering, Med-X Research Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
    Alstermark, Bror
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Lan, Ning
    Institute of Rehabilitation Engineering, Med-X Research Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
    Corticomuscular transmission of tremor signals by propriospinal neurons in Parkinson's disease.2013Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, nr 11, artikkel-id e79829Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cortical oscillatory signals of single and double tremor frequencies act together to cause tremor in the peripheral limbs of patients with Parkinson's disease (PD). But the corticospinal pathway that transmits the tremor signals has not been clarified, and how alternating bursts of antagonistic muscle activations are generated from the cortical oscillatory signals is not well understood. This paper investigates the plausible role of propriospinal neurons (PN) in C3-C4 in transmitting the cortical oscillatory signals to peripheral muscles. Kinematics data and surface electromyogram (EMG) of tremor in forearm were collected from PD patients. A PN network model was constructed based on known neurophysiological connections of PN. The cortical efferent signal of double tremor frequencies were integrated at the PN network, whose outputs drove the muscles of a virtual arm (VA) model to simulate tremor behaviors. The cortical efferent signal of single tremor frequency actuated muscle spindles. By comparing tremor data of PD patients and the results of model simulation, we examined two hypotheses regarding the corticospinal transmission of oscillatory signals in Parkinsonian tremor. Hypothesis I stated that the oscillatory cortical signals were transmitted via the mono-synaptic corticospinal pathways bypassing the PN network. The alternative hypothesis II stated that they were transmitted by way of PN multi-synaptic corticospinal pathway. Simulations indicated that without the PN network, the alternating burst patterns of antagonistic muscle EMGs could not be reliably generated, rejecting the first hypothesis. However, with the PN network, the alternating burst patterns of antagonist EMGs were naturally reproduced under all conditions of cortical oscillations. The results suggest that cortical commands of single and double tremor frequencies are further processed at PN to compute the alternating burst patterns in flexor and extensor muscles, and the neuromuscular dynamics demonstrated a frequency dependent damping on tremor, which may prevent tremor above 8 Hz to occur.

  • 121.
    Hedner, Margareta
    et al.
    Stockholm University, Stockholm Brain Institute.
    Nilsson, Lars-Göran
    Stockholm University, Stockholm Brain Institute.
    Olofsson, Jonas K
    Stockholm University, Stockholm Brain Institute.
    Bergman, Olle
    Göteborg University.
    Eriksson, Elias
    Göteborg University.
    Nyberg, Lars
    Umeå universitet, Samhällsvetenskapliga fakulteten, Centrum för befolkningsstudier (CBS). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Larsson, Maria
    Stockholm University, Stockholm Brain Institute.
    Age-related olfactory decline is associated with the BDNF Val66met Polymorphism: Evidence from a population-based study2010Inngår i: Frontiers in aging neuroscience, ISSN 1663-4365, Vol. 2, s. 24-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The present study investigates the effect of the brain-derived neurotrophic factor (BDNF) val66met polymorphism on change in olfactory function in a large scale, longitudinal population-based sample (n = 836). The subjects were tested on a 13 item force-choice odor identification test on two test occasions over a 5-year-interval. Sex, education, health-related factors, and semantic ability were controlled for in the statistical analyses. Results showed an interaction effect of age and BDNF val66met on olfactory change, such that the magnitude of olfactory decline in the older age cohort (70-90 years old at baseline) was larger for the val homozygote carriers than for the met carriers. The older met carriers did not display larger age-related decline in olfactory function compared to the younger group. The BDNF val66met polymorphism did not affect the rate of decline in the younger age cohort (45-65 years). The findings are discussed in the light of the proposed roles of BDNF in neural development and maintenance.

  • 122.
    Hultin, Magnus
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Anestesiologi och intensivvård.
    Edin, Benoni B.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Själander, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Medicin.
    Two Years Experiences of a new Swedish National Proficiency Test for Doctors of Medicine.2018Inngår i: Abstract book, undee, 2018Konferansepaper (Fagfellevurdert)
  • 123.
    Häger Ross, Charlotte
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    To grip and not to slip: sensorimotor mechanisms in reactive control of grasp stability1995Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The reactive control of fingertip forces maintaining grasp stability was examined in man during a prehensile task. Blindfolded subjects used the precision grip between the tips of index finger and thumb to restrain an object that was subjected to unpredictable load forces. These were delivered tangential to the parallel grip surfaces of the object. Load forces, grip forces (perpendicular to the grip surfaces) and position of the object were recorded.Subjects automatically adjusted the grip forces to loads of various amplitudes and rates. Thereby they maintained a reliable safety margin against frictional slips without using excessive grip forces. A rapid rise in grip force lasting about 0.2 s was triggered after a short delay following the onset of a sustained ramp load increase. This 'catch-up' response caused a quick restoration of an adequate grip:load force ratio that prevented frictional slips. If the ramp load continued to increase after the catchup response, the grip force also increased in parallel with the load change in a 'tracking' manner. Consequently, during the hold phases of 'ramp-and-hold' loads, the employed grip forces were approximately proportional to the load amplitude. Sensory information about the rate of change of the load force parametrically scaled the 'catchup' and 'tracking' responses.Following anesthetic block of sensory input from the digits, the grip responses were both delayed and attenuated or even abolished. To compensate for these impairments, subjects had to voluntarily maintain exceedingly high grip forces to prevent the object from slipping. The grip control improved slightly during hand and forearm support conditions that allowed marked wrist movements to occur in response to the loading. This indicates that signals from receptors in muscles, joints or skin areas proximal to the digits can to some extent be used to adjust grip forces during impaired digital sensibility. In contrast, these signals had only minor influence on the control during normal digital sensibility.Grip responses to loads delivered in various directions revealed that the load direction, in relation to gravity and to the hand's geometry, represents intrinsic task variables in the automatic processes that maintain a stable grasp. The load direction influenced both the response latencies and the magnitudes of the grip responses. The response latencies were shortest for loads in directions that were the most critical with regard to the consequences of frictional slippage, i.e., loads directed away from the palm or in the direction of gravity. Recordings of signals in cutaneous afferents innervating the finger tips demonstrated that these effects on the response latencies depended on differences in the time needed by the central nervous system to implement the motor responses. The short latencies in the most ‘criticar load directions may reflect the preparation of a default response, while additional central processing would be needed to execute the response to loads in other directions. Adjustments to local frictional anisotropies at the digit-object interface largely explained the magnitude effects.In conclusion, grip responses are automatically adjusted to the current loading condition during unpredictable loading of a hand held object. Subjects call up a previously acquired sensorimotor transform that supports grasp stability by preventing both object slippage and excessive grip forces. Cutaneous sensory information about tangential forces and frictional conditions at the digit-object interface is used to initiate and scale the grip responses to the current loading conditions, largely in a predictive manner.

  • 124.
    Häger-Ross, Charlotte
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Cole, KJ
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Grip-force responses to unanticipated object loading: load direction reveals body- and gravity-referenced intrinsic task variables1996Inngår i: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 110, nr 1, s. 142-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Humans preserve grasp stability by automatically regulating the grip forces when loads are applied tangentially to the grip surfaces of a manipulandum held in a precision grip. The effects of the direction of the load force in relation to the palm, trunk, and gravity were investigated in blindfolded subjects. Controlled, tangential load-forces were delivered in an unpredictable manner to the grip surface in contact with the index finger either in the distal and proximal directions (away from and toward the palm) or in the ulnar and radial directions (transverse to the palm). The hand was oriented in: (1) a standard position, with the forearm extended horizontally and anteriorly in intermediate pronosupination; (2) an inverted position, reversing the direction of radial and ulnar loads in relation to gravity; and (3) a horizontally rotated position, in which distal loads were directed toward the trunk. The amplitude of the grip-force responses (perpendicular to the grip surface) varied with the direction of load in a manner reflecting frictional anisotropies at the digit-object interface; that is, the subjects automatically scaled the grip responses to provide similar safety margins against frictional slips. For all hand positions, the time from onset of load increase to start of the grip-force increase was shorter for distal loads, which tended to pull the object out of the hand, than for proximal loads. Furthermore, this latency was shorter for loads in the direction of gravity, regardless of hand position. Thus, shorter latencies were observed when frictional forces alone opposed the load, while longer latencies occurred when gravity also opposed the load or when the more proximal parts of the digits and palm were positioned in the path of the load. These latency effects were due to different processing delays in the central nervous system and may reflect the preparation of a default response in certain critical directions. The response to loads in other directions would incur delays required to implement a new frictional scaling and a different muscle activation pattern to counteract the load forces. We conclude that load direction, referenced to gravity and to the hand's geometry, represents intrinsic task variables in the automatic processes that maintain a stable grasp on objects subjected to unpredictable load forces. In contrast, the grip-force safety margin against frictional slips did not vary systematically with respect to these task variables. Instead, the magnitude of the grip-force responses varied across load direction and hand orientation according to frictional differences providing similar safety margins supporting grasp stability.

  • 125.
    Häger-Ross, Charlotte
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nondigital afferent input in reactive control of fingertip forces during precision grip1996Inngår i: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 110, nr 1, s. 131-141Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sensory inputs from the digits are important in initiating and scaling automatic reactive grip responses that help prevent frictional slips when grasped objects are subjected to destabilizing load forces. In the present study we analyzed the contribution to grip-force control from mechanoreceptors located proximal to the digits when subjects held a small manipulandum between the tips of the thumb and index finger. Loads of various controlled amplitudes and rates were delivered tangential to the grip surfaces at unpredictable times. Grip forces (normal to the grip surfaces) and the position of the manipulandum were recorded. In addition, movements of hand and arm segments were assessed by recording the position of markers placed at critical points. Subjects performed test series during normal digital sensibility and during local anesthesia of the index finger and thumb. To grade the size of movements of tissues proximal to the digits caused by the loadings, three different conditions of arm and hand support were used; (1) in the hand-support condition the subjects used the three ulnar fingers to grasp a vertical dowel support and the forearm was supported in a vacuum cast; (2) in the forearm-support condition only the forearm was supported; finally, (3) in the no-support condition the arm was free. With normal digital sensibility the size of the movements proximal to the digits had small effects on the grip-force control. In contrast, the grip control was markedly influenced by the extent of such movements during digital anesthesia. The poorest control was observed in the hand-support condition, allowing essentially only digital movements. The grip responses were either absent or attenuated, with greatly prolonged onset latencies. In the forearm and no-support conditions, when marked wrist movements took place, both the frequency and the strength of grip-force responses were higher, and the grip response latencies were shorter. However, the performance never approached normal. It is concluded that sensory inputs from the digits are dominant in reactive grip control. However, nondigital sensory input may be used for some grip control during impaired digital sensibility. Furthermore, the quality of the control during impaired sensibility depends on the extent of movements evoked by the load in the distal, unanesthetized parts of the arm. The origin of these useful sensory signals is discussed.

  • 126. Isa, Tadashi
    et al.
    Ohki, Yukari
    Alstermark, Bror
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Pettersson, Lars-Gunnar
    Sasaki, Shigeto
    Direct and indirect cortico-motoneuronal pathways and control of hand/arm movements.2007Inngår i: Physiology, ISSN 1548-9213, Vol. 22, s. 145-52Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Recent studies from our group have demonstrated the existence of a disynaptic excitatory cortico-motoneuronal (CM) pathway in macaque monkeys via propriospinal neurons in the midcervical segments. Results from behavioral studies with lesion of the direct pathway suggest that the indirect CM pathway can mediate the command for dexterous finger movements.

  • 127. Isa, Tadashi
    et al.
    Ohki, Yukari
    Seki, Kazuhiko
    Alstermark, Bror
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    Properties of propriospinal neurons in the C3-C4 segments mediating disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey.2006Inngår i: Journal of Neurophysiology, ISSN 0022-3077, Vol. 95, nr 6, s. 3674-85Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Candidate propriospinal neurons (PNs) that mediate disynaptic pyramidal excitation to forelimb motoneurons were studied in the C3-C4 segments in anesthetized macaque monkeys (n = 10). A total of 177 neurons were recorded (145 extracellularly, 48 intracellularly, and 16 both) in laminae VI-VII. Among these, 86 neurons (73 extracellularly, 14 intracellularly and 1 both) were antidromically activated from the forelimb motor nucleus or from the ventrolateral funiculus just lateral to the motor nucleus in the C6/C7 segments and thus are identified as PNs. Among the 73 extracellularly recorded PNs, 60 cells were fired by a train of four stimuli to the contralateral pyramid with segmental latencies of 0.8-2.2 ms, with most of them (n = 52) in a monosynaptic range (<1.4 ms including one synaptic delay and time to firing). The firing probability was only 21% from the third pyramidal volley but increased to 83% after intravenous injection of strychnine. In most of the intracellularly recorded PNs, stimulation of the contralateral pyramid evoked monosynaptic excitatory postsynaptic potentials (EPSPs, 12/14) and disynaptic inhibitory postsynaptic potentials (14/14), which were found to be glycinergic. In contrast, cells that did not project to the C6-Th1 segments where forelimb motoneurons are located were classified as segmental interneurons. These were fired from the third pyramidal volley with a probability of 71% before injection of strychnine. It is proposed that some of these interneurons mediate feed-forward inhibition to the PNs. These results suggest that the C3-C4 PNs receive feed-forward inhibition from the pyramid in addition to monosynaptic excitation and that this inhibition is stronger in the macaque monkey than in the cat. Another difference with the cat was that only 26 of the 86 PNs (30%, as compared with 84% in the cat) with projection to the forelimb motor nuclei send ascending collaterals terminating in the lateral reticular nucleus (LRN) on the ipsilateral side of the medulla. Thus we identified C3-C4 PNs that could mediate disynaptic pyramidal excitation to forelimb motoneurons in the macaque monkey. The present findings explain why it was difficult in previous studies of the macaque monkey to evoke disynaptic pyramidal excitation via C3-C4 PNs in forelimb motoneurons and why-as compared with the cat-the monosynaptic EPSPs evoked from the LRN via C3-C4 PNs were smaller in amplitude.

  • 128.
    Jeneskog, Torgny
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    A descending pathway to dynamic fusimotor neurones and its possible relation to a climbing fibre system1974Doktoravhandling, med artikler (Annet vitenskapelig)
  • 129.
    Jenmalm, Per
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Birznieks, Ingvars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Goodwin, A. W.
    Johansson, Roland S
    Influences of object shape on responses in human tactile afferents under conditions characteristic for manipulationManuskript (Annet vitenskapelig)
  • 130.
    Jiang, Juan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Azim, Eiman
    Ekerot, Carl-Fredrik
    Alstermark, Bror
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Direct and indirect spino-cerebellar pathways: shared ideas but different functions in motor control2015Inngår i: Frontiers in Computational Neuroscience, ISSN 1662-5188, E-ISSN 1662-5188, Vol. 9, artikkel-id 75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impressive precision of mammalian limb movements relies on internal feedback pathways that convey information about ongoing motor output to cerebellar circuits. The spino-cerebellar tracts (SCT) in the cervical, thoracic and lumbar spinal cord have long been considered canonical neural substrates for the conveyance of internal feedback signals. Here we consider the distinct features of an indirect spino-cerebellar route, via the brainstem lateral reticular nucleus (LRN), and the implications of this pre-cerebellar "detour" for the execution and evolution of limb motor control. Both direct and indirect spino-cerebellar pathways signal spinal interneuronal activity to the cerebellum during movements, but evidence suggests that direct SCT neurons are mainly modulated by rhythmic activity, whereas the LRN also receives information from systems active during postural adjustment, reaching and grasping. Thus, while direct and indirect spinocerebellar circuits can both be regarded as internal copy pathways, it seems likely that the direct system is principally dedicated to rhythmic motor acts like locomotion, while the indirect system also provides a means of pre-cerebellar integration relevant to the execution and coordination of dexterous limb movements.

  • 131.
    Johansson, Anders
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Context dependent adaptation of biting behavior in human2014Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The focus of this thesis was to study an action that humans perform regularly, namely, to hold a morsel between the teeth and split it into smaller pieces. Three different issues related to this biting behavior were addressed:  (1) the effect of redu­c­ed perio­dontal tissues on food holding and splitting behavior; (2) the behavioral conse­quences of performing different bite tasks with different functional requirements, i.e., to split a peanut half resting on a piece of chocolate or to split both the peanut and the chocolate; and (3) the reflex modulations resul­ting from such a change in the intended bite action. The main conclusions from the experi­mental studies were the following:

    First, perio­dontitis, an inflam­matory disease that destroys the peri­o­dontal ligaments and the embedded perio­dontal mechanoreceptors, causes significant impairments in the masticatory abili­ty: the manipulative bite forces when holding a morsel are elevated compared to a matched control population and the bite force development prior to food split is altered. These changes are likely due to a combination of reduced sensory informa­tion from the damaged ligaments and to changes in the bite stra­tegy secon­d­ary to the unstable oral situation.

    Second, people exploit the anatomy of jaw-closing muscles to regulate the amount of bite force that dissipates following a sudden unloading of the jaw. Such control is necessary because without mechanisms that quickly halt jaw-closing movements after sudden unloading, the impact forces when the teeth collide could otherwise damage both the teeth and related soft tissues. Splitting a piece of chocolate, for instance, regularly requires >100N of bite force and the jaws collide within 5 ms of a split. On the other hand, when biting through heterogeneous food, the bite force needs to be kept high until the whole morsel is split. The required regulation is achieved by differen­tial­ly engaging parts of the masseter muscles along the anteroposterior axis of the jaw to exploit differences between muscle portions in their bite force generating capa­ci­ty and muscle shortening velocity.

    Finally, the reflex evoked by suddenly unloading the jaw—apparent only after the initial bite force dissipation—is modulated according to the bite intention. That is, when the intention is to bite through food items with multiple layers, the reflex response in the jaw opening muscles following a split is small, thus minimizing the bite force reduction. In contrast, when the intention is to rapidly decrease the bite force once a split has occurred, the reflex response is high. This pattern of reflex modulation is functionally beneficial when biting through heterogeneous food in a smooth manner.

    The presented studies show the significance of integrating cogni­tive, physiological and anatomical aspects when attempting to understand human masticatory control.

  • 132.
    Johansson, Anders Sixten
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Pruszynski, J Andrew
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Edin, Benoni Benjamin
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Westberg, Karl-Gunnar
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Biting intentions modulate digastric reflex responses to sudden unloading of the jaw2014Inngår i: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 112, nr 5, s. 1067-1073Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reflex responses in jaw opening muscles can be evoked when a brittle object cracks between the teeth and suddenly unloads the jaw. We hypothesized that this reflex response is flexible and, as such, is modulated according to the instructed goal of biting through an object. Study participants performed two different biting tasks when holding a peanut-half stacked on a chocolate piece between their incisors. In one task, they were asked to split the peanut-half only (single-split task) and, in the other task, they were asked to split both the peanut and the chocolate in one action (double-split task). In both tasks, the peanut split evoked a jaw opening muscle response, quantified from EMG recordings of the digastric muscle in a window 20-60 ms following peanut split. Consistent with our hypothesis, we found that the jaw opening muscle response in the single-split trials was about twice the size of the jaw opening muscle response in the double-split trials. A linear model that predicted the jaw opening muscle response on a single trial basis indicated that task settings played a significant role in this modulation but also that the pre-split digastric muscle activity contributed to the modulation. These findings demonstrate that, like reflex responses to mechanical perturbations in limb muscles, reflex responses in jaw muscles not only show gain-scaling but also are modulated by subject intent.

  • 133.
    Johansson, Anders
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Westberg, Karl-Gunnar
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Edin, Benoni B.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Task-dependent control of the jaw during food splitting in humans2014Inngår i: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 111, s. 2614-2623Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although splitting of food items between the incisors often requires high bite forces, rarely do the teeth harmfully collide when the jaw quickly closes after split. Previous studies indicate that the force-velocity relationship of the jaw closing muscles principally explains the prompt dissipation of jaw closing force. Here, we asked whether people could regulate the dissipation of jaw closing force during food splitting. We hypothesized that such regulation might be implemented via differential recruitment of masseter muscle portions situated along the anteroposterior axis because these portions will experience a different shortening velocity during jaw closure. Study participants performed two different tasks when holding a peanut-half stacked on a chocolate piece between their incisors. In one task, they were asked to split the peanut-half only (single-split trials) and, in the other, to split both the peanut and the chocolate in one action (double-split trials). In double-split trials following the peanut split, the intensity of the tooth impact on the chocolate piece was on average 2.5 times greater than in single-split trials, indicating a substantially greater loss of jaw closing force in the single-split trials. We conclude that control of jaw closing force dissipation following food splitting depends on task demands. Consistent with our hypothesis, converging neurophysiological and morphometric data indicated that this control involved a differential activation of the jaw closing masseter muscle along the anteroposterior axis. These latter findings suggest that the regulation of jaw closing force after sudden unloading of the jaw exploits masseter muscle compartmentalization.

  • 134.
    Johansson, Jonas
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Avdelningen för hållbar hälsa. Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Jarocka, Ewa
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Westling, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nordström, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Avdelningen för hållbar hälsa.
    Nordström, Peter
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Predicting incident falls: Relationship between postural sway and limits of stability in older adults2019Inngår i: Human Movement Science, ISSN 0167-9457, E-ISSN 1872-7646, Vol. 66, s. 117-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Background We have previously shown that objective measurements of postural sway predicts fall risk, although it is currently unknown how limits of stability (LOS) might influence these results.

    Research question: How integrated postural sway and LOS measurements predict the risk of incident falls in a population-based sample of older adults.

    Methods: The sample for this prospective observational study was drawn from the Healthy Ageing Initiative cohort and included data collected between June 2012 and December 2016 for 2396 men and women, all 70 years of age. LOS was compared to postural sway with measurements during eyes-open (EO) and eyes-closed (EC) trials, using the previously validated Wii Force Plate. Fall history was assessed during baseline examination and incident falls were collected during follow-up at 6 and 12 months. Independent predictors of incident falls and additional covariates were investigated using multiple logistic regression models.

    Results: During follow-up, 337 out of 2396 participants (14%) had experienced a fall. Unadjusted regression models from the EO trial revealed increased fall risk by 6% (OR 1.06, 95% CI 1.02–1.11) per each centimeter squared increase in sway area and by 16% (OR 1.16, 95% CI 1.07–1.25) per 1-unit increase in Sway-Area-to-LOS ratio. Odds ratios were generally lower when analyzing EC trials and only slightly attenuated in fully adjusted models.

    Significance: Integrating postural sway and LOS parameters provides valid fall risk prediction and a holistic analysis of postural stability. Future work should establish normative values and evaluate clinical utility of these measures.

  • 135.
    Johansson, R S
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Westling, G
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Bäckström, A
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, J R
    Queen's University, Kingston, Canada.
    Eye-hand coordination in object manipulation.2001Inngår i: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 21, nr 17, s. 6917-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We analyzed the coordination between gaze behavior, fingertip movements, and movements of the manipulated object when subjects reached for and grasped a bar and moved it to press a target-switch. Subjects almost exclusively fixated certain landmarks critical for the control of the task. Landmarks at which contact events took place were obligatory gaze targets. These included the grasp site on the bar, the target, and the support surface where the bar was returned after target contact. Any obstacle in the direct movement path and the tip of the bar were optional landmarks. Subjects never fixated the hand or the moving bar. Gaze and hand/bar movements were linked concerning landmarks, with gaze leading. The instant that gaze exited a given landmark coincided with a kinematic event at that landmark in a manner suggesting that subjects monitored critical kinematic events for phasic verification of task progress and subgoal completion. For both the obstacle and target, subjects directed saccades and fixations to sites that were offset from the physical extension of the objects. Fixations related to an obstacle appeared to specify a location around which the extending tip of the bar should travel. We conclude that gaze supports hand movement planning by marking key positions to which the fingertips or grasped object are subsequently directed. The salience of gaze targets arises from the functional sensorimotor requirements of the task. We further suggest that gaze control contributes to the development and maintenance of sensorimotor correlation matrices that support predictive motor control in manipulation.

  • 136.
    Johansson, Roland
    et al.
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    Birznieks, Ingvars
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    First spikes in ensembles of human tactile afferents code complex spatial fingertip events.2004Inngår i: Nature Neuroscience, ISSN 1097-6256, Vol. 7, nr 2, s. 170-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is generally assumed that primary sensory neurons transmit information by their firing rates. However, during natural object manipulations, tactile information from the fingertips is used faster than can be readily explained by rate codes. Here we show that the relative timing of the first impulses elicited in individual units of ensembles of afferents reliably conveys information about the direction of fingertip force and the shape of the surface contacting the fingertip. The sequence in which different afferents initially discharge in response to mechanical fingertip events provides information about these events faster than the fastest possible rate code and fast enough to account for the use of tactile signals in natural manipulation.

  • 137.
    Johansson, Roland
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, JR
    Queen’s University, Kingston, ON, Canada.
    Tactile sensory control of object manipulation in humans2008Inngår i: The senses, a comprehensive reference: somatotsensation Vol 6 / [ed] Esther Gardner, Jon H Kaas, Amsterdam: Elsevier , 2008, 1, Vol. 6, s. 67-86Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Dexterous object manipulation is a hallmark of human skill. The versatility of the human hands in manipulation tasks depends on both the anatomical structure of the hands and the neural machinery that controls them. Research during the last 20 years has led to important advances in our understanding of the sensorimotor control mechanisms that underlie dexterous object manipulation. This article focuses on the sensorimotor control of fingertip actions with special emphasis on the role of tactile sensory mechanisms. It highlights the importance of sensory predictions, especially related to mechanical contact events around which manipulation tasks are organized, and analyzes how such predictions are influenced by tactile afferent signals recorded in single neurons in awake humans.

  • 138.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Dynamic use of tactile afferent signals in control of dexterous manipulation.2002Inngår i: Advances in Experimental Medicine and Biology, ISSN 0065-2598, E-ISSN 2214-8019, Vol. 508, s. 397-410Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During object manipulation, humans select and activate neural action programs acquired during ontogenetic development. A basic issue in understanding the control of dexterous manipulation is to learn how people use sensory information to adapt the output of these neural programs such that the fingertip actions matches the requirements imposed by the physical properties of the manipulated object, e.g., weight (mass), slipperiness, shape, and mass distribution. Although visually based identification processes contribute to predictions of required fingertip actions, the digital tactile sensors provide critical information for the control of fingertip forces. The present account deals with the tactile afferent signals from the digits during manipulation and focuses on some specific issues that the neural controller has to deal with to make use of tactile information.

  • 139.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nervceller i samarbete2008Inngår i: Det friska och det sjuka nervsystemet, Umeå: Medicinska fakulteten , 2008Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 140.
    Johansson, Roland S
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, J Randall
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Coding and use of tactile signals from the fingertips in object manipulation tasks2009Inngår i: Nature Reviews Neuroscience, ISSN 1471-003X, E-ISSN 1471-0048, Vol. 10, nr 5, s. 345-359Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During object manipulation tasks, the brain selects and implements action-phase controllers that use sensory predictions and afferent signals to tailor motor output to the physical properties of the objects involved. Analysis of signals in tactile afferent neurons and central processes in humans reveals how contact events are encoded and used to monitor and update task performance.

  • 141.
    Johansson, Roland S
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, J Randall
    Umeå universitet, Medicinska fakulteten, Institutionen för odontologi.
    Sensorimotor control of manipulation2009Inngår i: Encyclopedia of Neuroscience, Elsevier , 2009, 8, s. 593-604Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 142.
    Johansson, Roland S
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, JR
    Sensory control of object manipulation2009Inngår i: Sensorimotor control of grasping: Physiology and pathophysiology / [ed] Dennis A. Nowak, Joachim Hermsdörfer., Cambridge: Cambridge books , 2009, s. 141-160Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Series of action phases characterize natural object manipulation tasks where each phase is responsible for satisfying a task subgoal. Subgoal attainment typically corresponds to distinct mechanical contact events, either involving the making or breaking of contact between the digits and an object or between a held object and another object. Subgoals are realized by the brain selecting and sequentially implementing suitable action-phase controllers that use sensory predictions and afferents signals in specific ways to tailor the motor output in anticipation of requirements imposed by objects' physical properties. This chapter discusses the use of tactile and visual sensory information in this context. It highlights the importance of sensory predictions, especially related to the discrete and distinct sensory events associated with contact events linked to subgoal completion, and considers how sensory signals influence and interact with such predictions in the control of manipulation tasks.

  • 143.
    Johansson, Roland S
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Häger, Charlotte
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Riso, Ronald
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Somatosensory control of precision grip during unpredictable pulling loads. II. Changes in load force rate.1992Inngår i: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 89, nr 1, s. 192-203Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the previous paper regarding the somatosensory control of the human precision grip, we concluded that the elicited automatic grip force adjustments are graded by the amplitude of the imposed loads when restraining an 'active' object subjected to unpredictable pulling forces (Johansson et al. 1992a). Using the same subjects and apparatus, the present study examines the capacity to respond to imposed load forces applied at various rates. Grip and load forces (forces normal and tangential to the grip surfaces) and the position of the object in the pulling direction (distal) were recorded. Trapezoidal load force profiles with plateau amplitudes of 2 N were delivered at the following rates of loading and unloading in an unpredictable sequence: 2 N/s, 4 N/s or 8 N/s. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N) were intermingled. The latencies between the start of the loading and the onset of the grip force response increased with decreasing load force rate. They were 80 +/- 9 ms, 108 +/- 13 ms, 138 +/- 27 ms and 174 +/- 39 ms for the 32, 8, 4 and 2 N/s rates, respectively. These data suggested that the grip response was elicited after a given minimum latency once a load amplitude threshold was exceeded. The amplitude of the initial rapid increase of grip force (i.e., the 'catch-up' response) was scaled by the rate of the load force, whereas its time course was similar for all load rates. This response was thus elicited as a unit, but its amplitude was graded by afferent information about the load rate arising very early during the loading. The scaling of the catch-up response was purposeful since it facilitated a rapid reconciliation of the ratio between the grip and load force to prevent slips. In that sense it apparently also compensated for the varying delays between the loading phase and the resultant grip force responses. However, modification of the catch-up response may occur during its course when the loading rate is altered prior to the grip force response or very early during the catch-up response itself. Hence, afferent information may be utilized continuously in updating the response although its motor expression may be confined to certain time contingencies. Moreover, this updating may take place after an extremely short latency (45-50 ms).

  • 144.
    Johansson, Roland S
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Riso, Ronald
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Häger, Charlotte
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Bäckström, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Somatosensory control of precision grip during unpredictable pulling loads. I. Changes in load force amplitude.1992Inngår i: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 89, nr 1, s. 181-191Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In manipulating 'passive' objects, for which the physical properties are stable and therefore predictable, information essential for the adaptation of the motor output to the properties of the current object is principally based on 'anticipatory parameter control' using sensorimotor memories, i.e., an internal representation of the object's properties based on previous manipulative experiences. Somatosensory afferent signals only intervene intermittently according to an 'event driven' control policy. The present study is the first in a series concerning the control of precision grip when manipulating 'active' objects that exert unpredictable forces which cannot be adequately represented in a sensorimotor memory. Consequently, the manipulation may be more reliant on a moment-to-moment sensory control. Subjects who were prevented from seeing the hand used the precision grip to restrain a manipulandum with two parallel grip surfaces attached to a force motor which produced distally directed (pulling) loads tangential to the finger tips. The trapezoidal load profiles consisted of a loading phase (4 N/s), plateau phase and an unloading phase (4 N/s) returning the load force to zero. Three force amplitudes were delivered in an unpredictable sequence; 1 N, 2 N and 4 N. In addition, trials with higher load rate (32 N/s) at a low amplitude (0.7 N), were superimposed on various background loads. The movement of the manipulandum, the load forces and grip forces (normal to the grip surfaces) were recorded at each finger. The grip force automatically changed with the load force during the loading and unloading phases. However, the grip responses were initiated after a brief delay. The response to the loading phase was characterized by an initial fast force increase termed the 'catch-up' response, which apparently compensated for the response delay--the grip force adequately matched the current load demands by the end of the catch-up response. In ramps with longer lasting loading phases (amplitude greater than or equal to 2 N) the catch-up response was followed by a 'tracking' response, during which the grip force increased in parallel with load force and maintained an approximately constant force ratio that prevented frictional slips. The grip force during the hold phase was linearly related to the load force, with an intercept close to the grip force used prior to the loading. Likewise, the grip force responses evoked by the fast loadings superimposed on existing loads followed the same linear relationship.(ABSTRACT TRUNCATED AT 400 WORDS)

  • 145.
    Johansson, Roland
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Theorin, Anna
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Westling, Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Andersson, Micael
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Ohki, Yukari
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    How a lateralized brain supports symmetrical bimanual tasks2006Inngår i: PLoS biology, ISSN 1544-9173, E-ISSN 1545-7885, Vol. 4, nr 6, s. e158-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A large repertoire of natural object manipulation tasks require precisely coupled symmetrical opposing forces by both hands on a single object. We asked how the lateralized brain handles this basic problem of spatial and temporal coordination. We show that the brain consistently appoints one of the hands as prime actor while the other assists, but the choice of acting hand is flexible. When study participants control a cursor by manipulating a tool held freely between the hands, the left hand becomes prime actor if the cursor moves directionally with the left-hand forces, whereas the right hand primarily acts if it moves with the opposing right-hand forces. In neurophysiological (electromyography, transcranial magnetic brain stimulation) and functional magnetic resonance brain imaging experiments we demonstrate that changes in hand assignment parallels a midline shift of lateralized activity in distal hand muscles, corticospinal pathways, and primary sensorimotor and cerebellar cortical areas. We conclude that the two hands can readily exchange roles as dominant actor in bimanual tasks. Spatial relationships between hand forces and goal motions determine hand assignments rather than habitual handedness. Finally, flexible role assignment of the hands is manifest at multiple levels of the motor system, from cortical regions all the way down to particular muscles.

  • 146.
    Johansson, Staffan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Yelhekar, Tushar D.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Druzin, Michael
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Commentary: Chloride Regulation: a Dynamic Equilibrium Crucial for Synaptic Inhibition2016Inngår i: Frontiers in Cellular Neuroscience, ISSN 1662-5102, E-ISSN 1662-5102, Vol. 10, artikkel-id 182Artikkel i tidsskrift (Fagfellevurdert)
  • 147.
    Jonasson, Lars
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Samhällsvetenskapliga fakulteten, Enheten för demografi och åldrandeforskning (CEDAR).
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Kramer, Arthur
    Departments of Psychology and Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA.
    Lundquist, Anders
    Umeå universitet, Samhällsvetenskapliga fakulteten, Handelshögskolan vid Umeå universitet, Statistik. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Riklund, Katrine
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Boraxbekk, Carl-Johan
    Umeå universitet, Samhällsvetenskapliga fakulteten, Enheten för demografi och åldrandeforskning (CEDAR). Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Hvidovre, Denmark.
    Aerobic Exercise Intervention, CognitivePerformance, and Brain Structure: results from the Physical Influences on Brain in Aging (PHIBRA) Study2017Inngår i: Frontiers in Aging Neuroscience, ISSN 1663-4365, E-ISSN 1663-4365, Vol. 8, s. 1-15, artikkel-id 336Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Studies have shown that aerobic exercise has the potential to improve cognition and reduce brain atrophy in older adults. However, the literature is equivocal with regards to the specificity or generality of these effects. To this end, we report results on cognitive function and brain structure from a 6-month training intervention with 60 sedentary adults (64–78 years) randomized to either aerobic training or stretching and toning control training. Cognitive functions were assessed with a neuropsychological test battery in which cognitive constructs were measured using several different tests. Freesurfer was used to estimate cortical thickness in frontal regions and hippocampus volume. Results showed that aerobic exercisers, compared to controls, exhibited a broad, rather than specific, improvement in cognition as indexed by a higher “Cognitive score,” a composite including episodic memory, processing speed, updating, and executive function tasks (p = 0.01). There were no group differences in cortical thickness, but additional analyses revealed that aerobic fitness at baseline was specifically related to larger thickness in dorsolateral prefrontal cortex (dlPFC), and hippocampus volume was positively associated with increased aerobic fitness over time. Moreover, “Cognitive score” was related to dlPFC thickness at baseline, but changes in “Cognitive score” and dlPFC thickness were associated over time in the aerobic group only. However, aerobic fitness did not predict dlPFC change, despite the improvement in “Cognitive score” in aerobic exercisers. Our interpretation of these observations is that potential exercise-induced changes in thickness are slow, and may be undetectable within 6-months, in contrast to change in hippocampus volume which in fact was predicted by the change in aerobic fitness. To conclude, our results add to a growing literature suggesting that aerobic exercise has a broad influence on cognitive functioning, which may aid in explaining why studies focusing on a narrower range of functions have sometimes reported mixed results.

  • 148.
    Jonasson, Lars S.
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Samhällsvetenskapliga fakulteten, Centrum för befolkningsstudier (CBS).
    Axelsson, Jan
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Riklund, Katrine
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Braver, Todd S.
    Department of Psychology,Washington University, St Louis, MO 63130, USA.
    Ögren, Mattias
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Bäckman, Lars
    Aging Research Center, Karolinska Institute, SE-113 30 Stockholm, Sweden.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Dopamine release in nucleus accumbens during rewarded task switching measured by [11C]raclopride2014Inngår i: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 99, s. 357-364Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Reward and motivation have positive influences on cognitive-control processes in numerous settings. Models of reward implicate corticostriatal loops and the dopamine (DA) system, with special emphasis on D2 receptors in nucleus accumbens (NAcc). In this study, 11 right-handed males (35-40 years) were scanned with positron emission tomography (PET) in a single [(11)C]raclopride dynamic scan during rewarded and non-rewarded task switching. Rewarded task switching (relative to baseline task switching) decreased [(11)C]raclopride binding in NAcc. Decreasing NAcc [(11)C]raclopride binding was strongly associated with task reaction time measures that reflect individual differences in effort and control strategies. Voxelwise analyses additionally revealed reward-related DA release in anterodorsal caudate, a region previously associated with task-switching. These PET findings provide evidence for striatal DA release during motivated cognitive control, and further suggest that NAcc DA release predicts the task reaction time benefits of reward incentives.

  • 149. Jones, Sari
    et al.
    Nyberg, Lars
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    Sandblom, Johan
    Stigsdotter Neely, Anna
    Ingvar, Martin
    Magnus Petersson, Karl
    Bäckman, Lars
    Cognitive and neural plasticity in aging: general and task-specific limitations.2006Inngår i: Neuroscience Biobehavioral Reviews, ISSN 0149-7634, Vol. 30, nr 6, s. 864-71Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    There is evidence for cognitive as well as neural plasticity across the adult life span, although aging is associated with certain constraints on plasticity. In the current paper, we argue that the age-related reduction in cognitive plasticity may be due to (a) deficits in general processing resources, and (b) failure to engage in task-relevant cognitive operations. Memory-training research suggests that age-related processing deficits (e.g., executive functions, speed) hinder older adults from utilizing mnemonic techniques as efficiently as the young, and that this age difference is reflected by diminished frontal activity during mnemonic use. Additional constraints on memory plasticity in old age are related to difficulties that are specific to the task, such as creating visual images, as well as in binding together the information to be remembered. These deficiencies are paralleled by reduced activity in occipito-parietal and medial-temporal regions, respectively. Future attempts to optimize intervention-related gains in old age should consider targeting both general processing and task-specific origins of age-associated reductions in cognitive plasticity.

  • 150.
    Jonsson, Bert
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Karlsson, Linnea
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB). Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Lithner, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Umeå forskningscentrum för matematikdidaktik (UFM). Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för naturvetenskapernas och matematikens didaktik.
    Liljekvist, Yvonne
    Karlstad University.
    Norqvist, Mathias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för matematik och matematisk statistik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för naturvetenskapernas och matematikens didaktik.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Mathematical Teaching Method affects Performance and Brain Activity2012Konferansepaper (Fagfellevurdert)
1234567 101 - 150 of 343
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf