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  • 251.
    Omrani, Mohsen
    et al.
    Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Pruszynski, J. Andrew
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Murnaghan, Chantelle D.
    Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada.
    Scott, Stephen H.
    Center for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada ; Department of Biomedical and Molecular Sciences, Kingston, Ontario, Canada ; Department of Medicine Queen's University, Kingston, Ontario, Canada.
    Perturbation-evoked responses in primary motor cortex are modulated by behavioral context2014Inngår i: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 112, nr 11, s. 2985-3000Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corrective responses to external perturbations are sensitive to the behavioral task being performed. It is believed that primary motor cortex (M1) forms part of a transcortical pathway that contributes to this sensitivity. Previous work has identified two distinct phases in the perturbation response of M1 neurons, an initial response starting similar to 20 ms after perturbation onset that does not depend on the intended motor action and a task- dependent response that begins similar to 40 ms after perturbation onset. However, this invariant initial response may reflect ongoing postural control or a task- independent response to the perturbation. The present study tested these two possibilities by examining if being engaged in an ongoing postural task before perturbation onset modulated the initial perturbation response in M1. Specifically, mechanical perturbations were applied to the shoulder and/ or elbow while the monkey maintained its hand at a central target or when it was watching a movie and not required to respond to the perturbation. As expected, corrective movements, muscle stretch responses, and M1 population activity in the late perturbation epoch were all significantly diminished in the movie task. Strikingly, initial perturbation responses (<40 ms postperturbation) remained the same across tasks, suggesting that the initial phase of M1 activity constitutes a task- independent response that is sensitive to the properties of the mechanical perturbation but not the goal of the ongoing motor task.

  • 252.
    Ottander, Ulrika
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Obstetrik och gynekologi.
    Leung, Constant HB
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Olofsson, Jan I
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Obstetrik och gynekologi.
    Functional evidence for divergent receptor activation mechanisms of luteotrophic and luteolytic events in the human corpus luteum1999Inngår i: Molecular human reproduction, ISSN 1360-9947, E-ISSN 1460-2407, Vol. 5, nr 5, s. 391-395Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using a dispersed human luteal cell culture model, progesterone synthesis following treatment by incremental doses of human chorionic gonadotrophin (HCG) and the stable prostaglandin F2alpha (PGF2alpha) analogue cloprostenol, alone or in combination, was related to corpora lutea (CL) mRNA transcript abundance coding for the luteinizing hormone (LH)/HCG receptor (LH-R) and PGF2alpha-receptor (FP) by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) in 33 otherwise healthy women, scheduled for surgery due to benign conditions. CL were grouped according to age, based on the occurrence of a preovulatory LH surge where post-LH days 2-5 were designated as early luteal phase, days 6-10 as mid-luteal phase and days 11-14 as late luteal phase. When exposed to HCG, maximal progesterone output was raised 2.2-fold (P = 0.08, n = 5) compared with untreated controls in the early CL, while it increased 5.7- and 4.6-fold in the mid- and late groups respectively (P<0.05, n = 4 mid-luteal phase, n = 3 late luteal phase). This stimulation pattern was found to be concordant with the value of mRNA coding for LH-R in all groups (n = 6 early luteal phase, n = 5 mid-luteal phase, n = 6 late luteal phase). The integrated response to HCG and cloprostenol showed a dose-dependent 60% inhibition of progesterone production; but only in late luteal phase luteal cells (P<0.01, n = 3). FP mRNA values were lowest in early luteal phase, and increased with the age of the CL. Interestingly, lowest CL tissue concentrations of the natural FP agonist PGF2alpha were found during mid-luteal phase while it increased again 1.6-fold during late luteal phase (P<0.05, n = 8 versus mid-luteal phase, n = 6). Collectively, these data demonstrate that (i) the extrinsic functional control (or rescue of CL in the event of pregnancy) occurs when the sensitivity towards LH/HCG is maximal; and (ii) the demise of CL function is mediated via an acquisition of sensitivity towards the intrinsic luteolytic signal, PGF2alpha in the ageing CL.

  • 253.
    Panarese, Alessandro
    et al.
    Scuola Superiore Sant’Anna, Pisa.
    Edin, Benoni B
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    A modified low-cost haptic interface as a tool for complex tactile stimulation2011Inngår i: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 33, nr 3, s. 386-390Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study describes the development and evaluation of a platform for the investigation of the human tactile ability. Specifically, it enables precise and reproducible application of time-varying 3D force stimuli to the skin of an immobilized human limb. We proceeded in the following steps: (1) programming a low-cost haptic interface to apply time-varying 3D force stimuli to a fixed rigid target, (2) implementing a combined feed-forward/feedback controller to improve the platform's precision and reliability in force stimulation, (3) determining the optimal tuning of the control loop parameters and (4) evaluating the system's performances when applying time-varying 3D force stimuli to an immobilized human finger pad. The system's performances were evaluated in terms of the accuracy and repeatability when delivering standard 3D force stimuli, i.e., stimuli with specified force components in the normal and skin tangential directions. Within the range of forces tested (5N in various directions), the maximum difference between the actual force and the desired value during static phases was <30mN (accuracy) and the root-mean-square of the standard deviation (repeatability) was 15mN during static phases and <75mN during dynamic phases.

  • 254.
    Panarese, Alessandro
    et al.
    Scuola Superiore Sant’Anna, Pisa.
    Edin, Benoni B
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Human ability to discriminate direction of three-dimensional force stimuli applied to the finger pad2011Inngår i: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 105, nr 2, s. 541-547Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Sensory information from tactile mechanoreceptors located in the glabrous skin of the hand is crucial for skillful object exploration and manipulation. These mechanoreceptors reliably encode the direction of fingertip forces, and the brain certainly relies on this information in both sensorimotor and cognitive tasks. In this study, we examined human ability to discriminate the direction of force stimuli applied to the volar surface of the index fingertip on the basis of tactile information only. We show that humans can discriminate three-dimensional (3D) force stimuli whose directions differ by an angle as small as 7.1 ° in the plane tangential to the skin surface. Moreover, we found that the discrimination ability was mainly affected by the time-varying phases of the stimulus, because adding a static plateau phase to the stimulus improved the discrimination threshold only to a limited extent.

  • 255. Panarese, Alessandro
    et al.
    Edin, Benoni B
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Vecchi, Fabrizio
    Carrozza, Maria C
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Humans can integrate force feedback to toes in their sensorimotor control of a robotic hand2009Inngår i: IEEE transactions on neural systems and rehabilitation engineering, ISSN 1534-4320, E-ISSN 1558-0210, Vol. 17, nr 6, s. 560-567Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tactile sensory feedback is essential for dexterous object manipulation. Users of hand myoelectric prostheses without tactile feedback must depend essentially on vision to control their device. Indeed, improved tactile feedback is one of their main priorities. Previous research has provided evidence that conveying tactile feedback can improve prostheses control, although additional effort is required to solve problems related to pattern recognition learning, unpleasant sensations, sensory adaptation, and low spatiotemporal resolution. Still, these studies have mainly focused on providing stimulation to hairy skin regions close to the amputation site, i.e., usually to the upper arm. Here, we explored the possibility to provide tactile feedback to the glabrous skin of toes, which have mechanical and neurophysiological properties similar to the fingertips. We explored this paradigm in a grasp-and-lift task, in which healthy participants controlled two opposing digits of a robotic hand by changing the spacing of their index finger and thumb. The normal forces applied by the robotic fingertips to a test object were fed back to the right big and second toe. We show that within a few lifting trials, all the participants incorporated the force feedback received by the foot in their sensorimotor control of the robotic hand.

  • 256.
    Papenberg, Goran
    et al.
    Aging Research Center, Karolinska Institutet and Stockholm University, Gävlegatan 16, 113 30, Stockholm, Sweden.
    Salami, Alireza
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Aging Research Center, Karolinska Institutet and Stockholm University, Gävlegatan 16, 113 30, Stockholm, Sweden.
    Persson, Jonas
    Aging Research Center, Karolinska Institutet and Stockholm University, Gävlegatan 16, 113 30, Stockholm, Sweden.
    Lindenberger, Ulman
    Berlin, Germany; London, UK.
    Bäckman, Lars
    Aging Research Center, Karolinska Institutet and Stockholm University, Gävlegatan 16, 113 30, Stockholm, Sweden.
    Genetics and Functional Imaging: Effects of APOE, BDNF, COMT, and KIBRA in Aging2015Inngår i: Neuropsychology Review, ISSN 1040-7308, E-ISSN 1573-6660, Vol. 25, nr 1, s. 47-62Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Increasing evidence from cross-sectional and longitudinal molecular-genetic studies suggests that effects of common genetic variations on cognitive functioning increase with aging. We review the influence of candidate genes on brain functioning in old age, focusing on four genetic variations that have been extensively investigated: APOE, BDNF, COMT, and KIBRA. Similar to the behavioral evidence, there are reports from age-comparative studies documenting stronger genetic effects on measures of brain functioning in older adults compared to younger adults. This pattern suggests disproportionate impairments of neural processing among older individuals carrying disadvantageous genotypes. We discuss various factors, including gene-gene interactions, study population characteristics, lifestyle factors, and diseases, that need to be considered in future studies and may help understand inconsistent findings in the extant literature.

  • 257.
    Persson, Jonas
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Bringlöv, Eva
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    The memory-enhancing effects of Ginseng and Ginkgo biloba in healthy volunteers2004Inngår i: Psychopharmacology, ISSN 0033-3158, E-ISSN 1432-2072, Vol. 172, nr 4, s. 430-434Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rationale: The use of herbal remedies, such as Ginkgo biloba and Ginseng, for improving cognitive performance has become increasingly popular during recent years. Several previous studies have indicated that administration of Ginkgo biloba and Ginseng may improve aspects of learning and memory in healthy volunteers. These results, however, are generally not supported by well-controlled clinical studies. Also, positive results have often been reported from studies investigating effects related to short-term, chronic administration of the extract. Nonetheless, both Ginkgo biloba and Ginseng are marketed as having the capacity to enhance cognitive functions, such as memory and learning, in the long term.

    Objective: This study aimed at investigating whether the use of Ginkgo biloba and Ginseng for a long period of time has positive effects on performance on learning and memory.

    Methods: Community-dwelling volunteers ( n=3500) from The Betula prospective cohort study: memory, health, and aging were included in the study.

    Results: It was found that the use of neither Ginkgo biloba ( n=40) nor Ginseng ( n=86) was associated with enhanced memory performance in any of the eight memory tests examined, relative to control groups either using or not using nutritional supplements.

    Conclusions: These findings indicate that use of Ginkgo biloba or Ginseng does not provide any quantifiable beneficial effects on memory performance in the long-term in healthy adult volunteers.

  • 258.
    Persson, Jonas
    et al.
    Department of Psychology, Stockholm University, 106 91 Stockholm, Sweden.
    Kalpouzos, Grégoria
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University, 106 91 Stockholm, Sweden.
    Ryberg, Mats
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Medicin.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Preserved hippocampus activation in normal aging as revealed by fMRI.2011Inngår i: Hippocampus, ISSN 1050-9631, E-ISSN 1098-1063, Vol. 21, nr 7, s. 753-766Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hippocampus is deteriorated in various pathologies such as Alzheimer's disease (AD) and such deterioration has been linked to memory impairment. By contrast, the structural and functional effects of normal aging on the hippocampus is a matter of debate, with some findings suggesting deterioration and others providing evidence of preservation. This constitutes a crucial question since many investigations on AD are based on the assumption that the deterioration of the hippocampus is the breaking point between normal and pathological aging. A growing number of fMRI studies specifically aimed at investigating hippocampal engagement in various cognitive tasks, notably memory tasks, but the results have been inconclusive. Here, we optimized the episodic face-name paired-associates task in order to test the functioning of the hippocampus in normal aging. Critically, we found no difference in the activation of the hippocampus between the young and a group of older participants. Analysis of individual patterns of activation substantiated this impression. Collectively, these findings provide evidence of preserved hippocampal functioning in normal aging.

  • 259. Persson, Jonas
    et al.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Altered brain activity in healthy seniors: what does it mean?2006Inngår i: Progress in Brain Research, ISSN 0079-6123, E-ISSN 1875-7855, Vol. 157, s. 45-56Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Age-related performance decreases are frequently observed on various memory tasks. Recent brain imaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) suggest a link between altered patterns of brain activity in older adults and memory performance. Convergent neuroimaging evidence shows that older adults have decreased activity in multiple regions important for memory tasks. Such relative under-activation in older adults is likely related to age-related reductions in cognitive performance. Age-comparative neuroimaging studies have also provided convincing support for regional over-activation by older adults. Such findings indicate that the older brain can re-organize to better cope with cognitive and other challenges. Although over-activation may play a compensatory role when cognitive decline is limited, under-activation seems to be the typical pattern when cognitive impairment is in a more progressed state. This pattern of age-related changes suggests that compensation through over-activation is restricted to the early stages of cognitive impairment in aging.

  • 260.
    Persson, Jonas
    et al.
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Pudas, Sara
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Lind, Johanna
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Kauppi, Karolina
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Nilsson, Lars-Göran
    Stockholm Univ, Dept Psychol, S-10691 Stockholm, Sweden .
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Longitudinal structure-function correlates in elderly reveal MTL dysfunction with cognitive decline2012Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 22, nr 10, s. 2297-2304Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By integrating behavioral measures and imaging data, previous investigations have explored the relationship between biological markers of aging and cognitive functions. Evidence from functional and structural neuroimaging has revealed that hippocampal volume and activation patterns in the medial temporal lobe (MTL) may predict cognitive performance in old age. Most past demonstrations of age-related differences in brain structure-function were based on cross-sectional comparisons. Here, the relationship between 6-year intraindividual change in functional magnetic resonance imaging (fMRI) signal and change in memory performance over 2 decades was examined. Correlations between intraindividual change in fMRI signal during episodic encoding and change in memory performance measured outside of scanning were used as an estimate for relating brain-behavior changes. The results revealed a positive relationship between activation change in the hippocampus (HC) and change in memory performance, reflecting reduced hippocampal activation in participants with declining performance. Using a similar analytic approach as for the functional data, we found that individuals with declining performance had reduced HC volume compared with individuals with intact performance. These observations provide a strong link between cognitive change in older adults and MTL structure and function and thus provide insights into brain correlates of individual variability in aging trajectories.

  • 261.
    Persson, Jonas
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Department of Psychology, Aging Research Center (ARC) at Karolinska Institute and Stockholm University, Stockholm, Sweden and Department of Psychology, Stockholm University, Stockholm, Sweden.
    Pudas, Sara
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Department of Psychology, Stockholm University, Stockholm, Sweden.
    Nilsson, Lars-Göran
    Karolinska Inst, Aging Res Ctr ARC, S-11330 Stockholm, Sweden and Stockholm Univ, Dept Psychol, S-11330 Stockholm, Sweden.
    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.
    Longitudinal assessment of default-mode brain function in aging2014Inngår i: Neurobiology of Aging, ISSN 0197-4580, E-ISSN 1558-1497, Vol. 35, nr 9, s. 2107-2117Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Age-related changes in the default-mode network (DMN) have been identified in prior cross-sectional functional magnetic resonance imaging studies. Here, we investigated longitudinal change in DMN activity and connectivity. Cognitively intact participants (aged 49-79 years at baseline) were scanned twice, with a 6-year interval, while performing an episodic memory task interleaved with a passive control condition. Longitudinal analyses showed that the DMN (control condition > memory task) could be reliably identified at both baseline and follow-up. Differences in the magnitude of task-induced deactivation in posterior DMN regions were observed between baseline and follow-up indicating reduced deactivation in these regions with increasing age. Although no overall longitudinal changes in within-network connectivity were found across the whole sample, individual differences in memory change correlated with change in connectivity. Thus, our results show stability of whole-brain DMN topology and functional connectivity over time in healthy older adults, whereas within-region DMN analyses show reduced deactivation between baseline and follow-up. The current findings provide novel insights into DMN functioning that may assist in identifying brain changes in patient populations, as well as characterizing factors that distinguish between normal and pathologic aging.

  • 262. Pettersson, L-G
    et al.
    Alstermark, Bror
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    Blagovechtchenski, E
    Isa, T
    Sasaski, S
    Skilled digit movements in feline and primate--recovery after selective spinal cord lesions.2007Inngår i: Acta Physiologica, ISSN 1748-1708, Vol. 189, nr 2, s. 141-54Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Recovery of voluntary movements after partial spinal cord injury depends, in part, on a take-over of function via unlesioned pathways. Using precise forelimb movements in the cat as model, spinal pathways contributing to motor restitution have been investigated in more detail. The food-taking movement by which the cat graSPS a morsel of food with the digits and brings it to the mouth is governed by interneurones in the forelimb segments (C6-Th1) and is normally controlled via the cortico- and rubrospinal tracts. Food-taking disappears after transection of these pathways in the dorsal part of the lateral funiculus (DLF) in C5/C6, but then recovers during a period of 2-3 weeks. Experiments with double lesions showed that the recovery depends on a take-over via ipsilateral ventral systems; a ventrally descending pathway, most probably cortico-reticulospinal, and a pathway via propriospinal neurones in the C3-C4 segments. It is postulated that the recovery involves a plastic reorganization of these systems. Dexterous finger movements in the macaque monkey are generally considered to depend on the monosynaptic cortico-motoneuronal (CM) connexion, which is lacking in the cat. Such movements are abolished after pyramidotomy at the level of the trapezoid body. However, experiments with transection of the corticospinal tract in the DLF and partly ventral part of the lateral funiculus in C5, showed a fast (1-28 days) recovery of precision grip and, to some extent, independent finger movements. Deficits in preshaping during the final approach to the morsel as well as lack of force were observed. A C5 DLF lesion spares corticofugal pathways to the brainstem and upper cervical segments. It is suggested that indirect corticomotoneuronal pathways may provide for recovery of dexterous finger movements and that the role of CM pathways for such movements should be broadened to include not only the monosynaptic connexion.

  • 263. Pinpin, L K
    et al.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Laschi, C
    Dario, P
    Gaze Interface: Utilizing Human Predicitive Gaze Movements for Controlling a Robotic Artefact2008Inngår i: 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, Pisa: Primo Congresso Nazionale di Bioingegneria , 2008Konferansepaper (Fagfellevurdert)
  • 264. Pinpin, LK
    et al.
    Johansson, Roland
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Laschi, C
    Dario, P
    Gaze interface: Utilizing human predictive gaze movements for controlling a HBS.2008Inngår i: 2nd IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, 2008, s. 158-162Konferansepaper (Fagfellevurdert)
  • 265.
    Pruszynski, J Andrew
    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.
    Edge-orientation processing in first-order tactile neurons2014Inngår i: Nature Neuroscience, ISSN 1097-6256, E-ISSN 1546-1726, Vol. 17, nr 10, s. 1404-1409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fundamental feature of first-order neurons in the tactile system is that their distal axon branches in the skin and forms many transduction sites, yielding complex receptive fields with many highly sensitive zones. We found that this arrangement constitutes a peripheral neural mechanism that allows individual neurons to signal geometric features of touched objects. Specifically, we observed that two types of first-order tactile neurons that densely innervate the glabrous skin of the human fingertips signaled edge orientation via both the intensity and the temporal structure of their responses. Moreover, we found that the spatial layout of a neuron's highly sensitive zones predicted its sensitivity to particular edge orientations. We submit that peripheral neurons in the touch-processing pathway, as with peripheral neurons in the visual-processing pathway, perform feature extraction computations that are typically attributed to neurons in the cerebral cortex.

  • 266.
    Pruszynski, J. Andrew
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Queen’s University, Kingston, Ontario.
    Kurtzer, Isaac
    New York College of Osteopathic Medicine, Queen’s University, Kingston, Ontario, New York College of Osteopathic Medicine, Old Westbury, New York.
    Nashed, Joseph Y.
    Queen’s University, Kingston, Ontario.
    Omrani, Mohsen
    Queen’s University, Kingston, Ontario.
    Brouwer, Brenda
    Queen’s University, Kingston, Ontario.
    Scott, Stephen H.
    Queen’s University, Kingston, Ontario.
    Primary motor cortex underlies multi-joint integration for fast feedback control2011Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 478, nr 7369, s. 387-390Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A basic difficulty for the nervous system is integrating locally ambiguous sensory information to form accurate perceptions about the outside world(1-4). This local-to-global problem is also fundamental to motor control of the arm, because complex mechanical interactions between shoulder and elbow allow a particular amount of motion at one joint to arise from an infinite combination of shoulder and elbow torques(5). Here we show, in humans and rhesus monkeys, that a transcortical pathway through primary motor cortex (M1) resolves this ambiguity during fast feedback control. We demonstrate that single M1 neurons of behaving monkeys can integrate shoulder and elbow motion information into motor commands that appropriately counter the underlying torque within about 50 milliseconds of a mechanical perturbation. Moreover, we reveal a causal link between M1 processing and multi-joint integration in humans by showing that shoulder muscle responses occurring 50 milliseconds after pure elbow displacement can be potentiated by transcranial magnetic stimulation. Taken together, our results show that transcortical processing through M1 permits feedback responses to express a level of sophistication that rivals voluntary control; this provides neurophysiological support for influential theories positing that voluntary movement is generated by the intelligent manipulation of sensory feedback(6,7).

  • 267.
    Pruszynski, J Andrew
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Centre for Neuroscience Studies, Queen's University, Kingston, Ontario K7L 3N6, Canada.
    Omrani, Mohsen
    Centre for Neuroscience Studies, Queen's University, Kingston, Ontario K7L 3N6, Canada.
    Scott, Stephen H
    Centre for Neuroscience Studies, Departments of Biomedical and Molecular Sciences, and Medicine, Queen's University, Kingston, Ontario K7L 3N6, Canada.
    Goal-dependent modulation of fast feedback responses in primary motor cortex2014Inngår i: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 34, nr 13, s. 4608-4617Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many human studies have demonstrated that rapid motor responses (i.e., muscle-stretch reflexes) to mechanical perturbations can be modified by a participant's intended response. Here, we used a novel experimental paradigm to investigate the neural mechanisms that underlie such goal-dependent modulation. Two monkeys positioned their hand in a central area against a constant load and responded to mechanical perturbations by quickly placing their hand into visually defined spatial targets. The perturbation was chosen to excite a particular proximal arm muscle or isolated neuron in primary motor cortex and two targets were placed so that the hand was pushed away from one target (OUT target) and toward the other (IN target). We chose these targets because they produced behavioral responses analogous to the classical verbal instructions used in human studies. A third centrally located target was used to examine responses with a constant goal. Arm muscles and neurons robustly responded to the perturbation and showed clear goal-dependent responses ∼35 and 70 ms after perturbation onset, respectively. Most M1 neurons and all muscles displayed larger perturbation-related responses for the OUT target than the IN target. However, a substantial number of M1 neurons showed more complex patterns of target-dependent modulation not seen in muscles, including greater activity for the IN target than the OUT target, and changes in target preference over time. Together, our results reveal complex goal-dependent modulation of fast feedback responses in M1 that are present early enough to account for goal-dependent stretch responses in arm muscles.

  • 268.
    Pruszynski, J. Andrew
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Queen’s University, Kingston.
    Scott, Stephen H.
    Queen’s University, Kingston.
    Optimal feedback control and the long-latency stretch response2012Inngår i: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 218, nr 3, s. 341-359Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    There has traditionally been a separation between voluntary control processes and the fast feedback responses which follow mechanical perturbations (i.e., stretch "reflexes"). However, a recent theory of motor control, based on optimal control, suggests that voluntary motor behavior involves the sophisticated manipulation of sensory feedback. We have recently proposed that one implication of this theory is that the long-latency stretch "reflex", like voluntary control, should support a rich assortment of behaviors because these two processes are intimately linked through shared neural circuitry including primary motor cortex. In this review, we first describe the basic principles of optimal feedback control related to voluntary motor behavior. We then explore the functional properties of upper-limb stretch responses, with a focus on how the sophistication of the long-latency stretch response rivals voluntary control. And last, we describe the neural circuitry that underlies the long-latency stretch response and detail the evidence that primary motor cortex participates in sophisticated feedback responses to mechanical perturbations.

  • 269.
    Pudas, Sara
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Persson, Jonas
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Josefsson, Maria
    Umeå universitet, Samhällsvetenskapliga fakulteten, Handelshögskolan vid Umeå universitet, Statistik.
    de Luna, Xavier
    Umeå universitet, Samhällsvetenskapliga fakulteten, Statistiska institutionen.
    Nilsson, Lars-Göran
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper.
    Brain Characteristics of Individuals Resisting Age-Related Cognitive Decline over Two Decades2013Inngår i: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 33, nr 20, s. 8668-8677Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Some elderly appear to resist age-related decline in cognitive functions, but the neural correlates of successful cognitive aging are not well known. Here, older human participants from a longitudinal study were classified as successful or average relative to the mean attrition-corrected cognitive development across 15-20 years in a population-based sample (n = 1561). Fifty-one successful elderly and 51 age-matched average elderly (mean age: 68.8 years) underwent functional magnetic resonance imaging while performing an episodic memory face-name paired-associates task. Successful older participants had higher BOLD signal during encoding than average participants, notably in the bilateral PFC and the left hippocampus (HC). The HC activation of the average, but not the successful, older group was lower than that of a young reference group (n = 45, mean age: 35.3 years). HC activation was correlated with task performance, thus likely contributing to the superior memory performance of successful older participants. The frontal BOLD response pattern might reflect individual differences present from young age. Additional analyses confirmed that both the initial cognitive level and the slope of cognitive change across the longitudinal measurement period contributed to the observed group differences in BOLD signal. Further, the differences between the older groups could not be accounted for by differences in brain structure. The current results suggest that one mechanism behind successful cognitive aging might be preservation of HC function combined with a high frontal responsivity. These findings highlight sources for heterogeneity in cognitive aging and may hold useful information for cognitive intervention studies.

  • 270.
    Pudas, Sara
    et al.
    Department of Psychology, Stockholm University, Stockholm, Sweden .
    Persson, Jonas
    Department of Psychology, Stockholm University, Stockholm, Sweden .
    Nilsson, Lars-Göran
    Department of Psychology, Stockholm University, Stockholm, Sweden .
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Maintenance and manipulation in working memory: Differential ventral and dorsal frontal cortex fMRI activity2009Inngår i: Acta Psychologica Sinica, ISSN 0439-755X, Vol. 41, nr 11, s. 1054-1062Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A verbal working memory protocol was designed and evaluated on a group of healthy younger adults in preparation for a large-scale functional magnetic resonance (fMRI) study on aging and memory. Letters were presented in two critical conditions: (i) maintenance, in which letters were to be memorized and kept in mind over a four second interval, and (ii) manipulation, in which letters were shifted forward in alphabetical order, and the new order was kept in mind. Analyses of fMRI data showed that the protocol elicited reliable activation in the frontal cortex, with manipulation producing more extensive activation patterns, both in whole-brain analyses and in predefined regions of interest (ROIs). There was also a distinction between dorsal and ventral lateral prefrontal regions, such that manipulation elicited more dorsolateral prefrontal activation. The protocol also elicited activation in various subcortical areas, previously associated with working-memory tasks. It was concluded that this working memory protocol is appropriate for investigating age-related changes in frontal-cortex functioning.

  • 271.
    Pudas, Sara
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Department of Psychology, Stockholm University, Stockholm.
    Persson, Jonas
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Department of Psychology, Stockholm University, Aging Research Center, Karolinska Institute and Stockholm University, Stockholm.
    Nilsson, Lars-Göran
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Aging Research Center, Karolinska Institute and Stockholm University, Stockholm.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Midlife memory ability accounts for brain activity differences in healthy aging2014Inngår i: Neurobiology of Aging, ISSN 0197-4580, E-ISSN 1558-1497, Vol. 35, nr 11, s. 2495-2503Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cross-sectional neuroimaging studies suggest that hippocampal and prefrontal cortex functions underlie individual differences in memory ability in older individuals, but it is unclear how individual differences in cognitive ability in youth contribute to cognitive and neuroimaging measures in older age. Here, we investigated the relative influences of midlife memory ability and age-related memory change on memory-related BOLD-signal variability at one time point, using a sample from a longitudinal population-based aging study (N = 203, aged 55-80 years). Hierarchical regression analyses showed that midlife memory ability, assessed 15-20 years earlier, explained at least as much variance as memory change in clusters in the left inferior prefrontal cortex and the bilateral hippocampus, during memory encoding. Furthermore, memory change estimates demonstrated higher sensitivity than current memory levels in identifying distinct frontal regions where activity was selectively related to age-related memory change, as opposed to midlife memory. These findings highlight challenges in interpreting individual differences in neurocognitive measures as age-related changes in the absence of longitudinal data and also demonstrate the improved sensitivity of longitudinal measures.

  • 272.
    Ramser, Kerstin
    et al.
    Luleå University of Technology.
    Malinina, Evgenya
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Luleå University of Technology.
    Candefjord, Stefan
    Luleå University of Technology.
    Resonance micro-raman investigations of the rat medial preoptic nucleus: effects of a low-iron diet on the neuroglobin content2012Inngår i: Applied Spectroscopy, ISSN 0003-7028, E-ISSN 1943-3530, Vol. 66, nr 12, s. 1454-1460Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The aim of this study was to investigate the medial preoptic nucleus (MPN) of the anterior hypothalamus by resonance Raman spectroscopy (514.5 nm) to determine if it is possible to enhance the Raman scattering of hemoproteins in fresh brain tissue slices. The resonance effect was compared with near-infrared Raman spectra. Two groups of male Sprague Dawley rats were studied, one control group on a normal diet and one group on a low-iron diet to evoke iron deficiency. Each group consisted of four rats, 38-41 days old. The diets lasted for 11, 12, and 15 days. The MPN regions of brain tissue slices were analyzed by monitoring raw and pre-processed mean data, by cluster analysis, and by deriving difference spectra from pre-processed mean spectra. Cluster analysis of the resonance Raman spectra could identify different hemoprotein groups, namely, hemoglobin (Hb) and neuroglobin (Ngb). Spectra from randomly distributed spots revealed high Hb content, whereas Ngb was evenly distributed in the MPN. The different spectra showed a decrease of the Ngb and lipid content for the animals on the low-iron diet. The Ngb decrease was approximately 20%. The data show that resonance Raman spectroscopy is well suited to study hemoproteins in fresh brain tissue.

  • 273. Reichelt, Andreas F
    et al.
    Ash, Alyssa M
    Baugh, Lee A
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, J Randall
    Adaptation of lift forces in object manipulation through action observation.2013Inngår i: Experimental Brain Research, ISSN 0014-4819, E-ISSN 1432-1106, Vol. 228, nr 2, s. 221-234Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ability to predict accurately the weights of objects is essential for skilled and dexterous manipulation. A potentially important source of information about object weight is through the observation of other people lifting objects. Here, we tested the hypothesis that when watching an actor lift an object, people naturally learn the object's weight and use this information to scale forces when they subsequently lift the object themselves. Participants repeatedly lifted an object in turn with an actor. Object weight unpredictably changed between 2 and 7 N every 5th to 9th of the actor's lifts, and the weight lifted by the participant always matched that previously lifted by the actor. Even though the participants were uninformed about the structure of the experiment, they appropriately adapted their lifting force in the first trial after a weight change. Thus, participants updated their internal representation about the object's weight, for use in action, when watching a single lift performed by the actor. This ability presumably involves the comparison of predicted and actual sensory information related to actor's actions, a comparison process that is also fundamental in action.

  • 274. Rotman, Gerben
    et al.
    Troje, Nikolaus F
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, J Randall
    Eye movements when observing predictable and unpredictable actions.2006Inngår i: Journal of Neurophysiology, ISSN 0022-3077, Vol. 96, nr 3, s. 1358-69Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We previously showed that, when observers watch an actor performing a predictable block-stacking task, the coordination between the observer's gaze and the actor's hand is similar to the coordination between the actor's gaze and hand. Both the observer and the actor direct gaze to forthcoming grasp and block landing sites and shift their gaze to the next grasp or landing site at around the time the hand contacts the block or the block contacts the landing site. Here we compare observers' gaze behavior in a block manipulation task when the observers did and when they did not know, in advance, which of two blocks the actor would pick up first. In both cases, observers managed to fixate the target ahead of the actor's hand and showed proactive gaze behavior. However, these target fixations occurred later, relative to the actor's movement, when observers did not know the target block in advance. In perceptual tests, in which observers watched animations of the actor reaching partway to the target and had to guess which block was the target, we found that the time at which observers were able to correctly do so was very similar to the time at which they would make saccades to the target block. Overall, our results indicate that observers use gaze in a fashion that is appropriate for hand movement planning and control. This in turn suggests that they implement representations of the manual actions required in the task and representations that direct task-specific eye movements.

  • 275.
    Rudner, Mary
    et al.
    The Swedish Institute for Disability Research, Department of Behavioural Sciences, Linköping University, Linköping, Sweden.
    Fransson, Peter
    Cognitive Neurophysiology, MR Research Centre, N8, Department of Clinical Neuroscience, Karolinska University Hospital, Stockholm, Sweden.
    Ingvar, Martin
    Cognitive Neurophysiology, MR Research Centre, N8, Department of Clinical Neuroscience, Karolinska University Hospital, Stockholm, Sweden.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Rönnberg, Jerker
    The Swedish Institute for Disability Research, Department of Behavioural Sciences, Linköping University, Linköping, Sweden.
    Neural representation of binding lexical signs and words in the episodic buffer of working memory2007Inngår i: Neuropsychologia, ISSN 0028-3932, E-ISSN 1873-3514, Vol. 45, nr 10, s. 2258-2276Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The episodic buffer accommodates formation and maintenance of unitary multidimensional representations based on information in different codes from different sources. Formation, based on submorphemic units, engages posterior brain regions, while maintenance engages frontal regions. Using a hybrid fMRI design, that allows separate analysis of transient and sustained components, an n-back task and an experimental group of 13 hearing native signers, with experience of Swedish Sign Language and Swedish since birth, we investigated binding of lexical signs and words in working memory. Results show that the transient component of these functions is supported by a buffer-specific network of posterior regions including the right middle temporal lobe, possibly relating to binding of phonological loop representations with semantic representations in long-term memory, as well as a loop-specific network, in line with predictions of a functional relationship between loop and buffer. The left hippocampus was engaged in transient and sustained components of buffer processing, possibly reflecting the meaningful nature of the stimuli. Only a minor role was found for executive functions in line with other recent work. A novel representation of the sustained component of working memory for audiovisual language in the right inferior temporal lobe may be related to perception of speech-related facial gestures. Previous findings of sign and speech loop representation in working memory were replicated and extended. Together, these findings support the notion of a module that mediates between codes and sources, such as the episodic buffer, and further our understanding of its nature.

  • 276. Saal, Hannes P
    et al.
    Vijayakumar, Sethu
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Information about complex fingertip parameters in individual human tactile afferent neurons2009Inngår i: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 29, nr 25, s. 8022-8031Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although information in tactile afferent neurons represented by firing rates has been studied extensively over nearly a century, recent studies suggest that precise spike timing might be more important than firing rates. Here, we used information theory to compare the information content in the discharges of 92 tactile afferents distributed over the entire terminal segment of the fingertip when it was contacted by surfaces with different curvatures and force directions representative of everyday manipulations. Estimates of the information content with regard to curvature and force direction based on the precise timing of spikes were at least 2.2 times and 1.6 times, respectively, larger than that of spike counts during a 125 ms period of force increase. Moreover, the information regarding force direction based on the timing of the very first elicited spike was comparable with that provided by spike counts and more than twice as large with respect to object shape. For all encoding schemes, afferents terminating close to the stimulation site tended to convey more information about surface curvature than more remote afferents that tended to convey more information about force direction. Finally, coding schemes based on spike timing and spike counts overall contributed mostly independent information. We conclude that information about tactile stimuli in timing of spikes in primary afferents, even if limited to the first spikes, surpasses that contained in firing rates and that these measures of afferents' responses might capture different aspects of the stimulus.

  • 277.
    Sailer, Uta
    et al.
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    Eggert, Thomas
    Straube, Andreas
    Impaired temporal prediction and eye-hand coordination in patients with cerebellar lesions.2005Inngår i: Behavioural Brain Research, ISSN 0166-4328, Vol. 160, nr 1, s. 72-87Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigated the effect of cerebellar lesions on temporal prediction and coordination in eye and hand movements. Nine patients with cerebellar lesions were compared to controls while they made saccades with and without simultaneous pointing movements towards a target that was either temporally predictable or non-predictable. The direction and amplitude of the target step was always predictable. Patients made much more early and late saccades than controls, but an equal amount of visually triggered saccades. This suggests that inappropriate saccades could be suppressed during the preparation of a goal-directed saccade. Hand movement frequency did not differ between both groups. Thus, cerebellar lesions can induce inappropriate saccades more easily than inappropriate hand movements. Controls, but not patients, generated visually triggered saccades of shorter latencies when the target was temporally predictable. Thus, the patients could not use information about target timing to synchronise visually triggered saccades with the target. They could, however, use this information to improve the suppression of inappropriate saccades. Regarding coordination, patients showed impairments in synchronising saccades with hand movements. Nevertheless, hand movements led to an enhancement of anticipatory saccades in patients as in controls. Moreover, hand movements and temporal predictability affected saccadic accuracy in both groups similarly. These results suggest that cerebellar lesions do not generally prevent access to temporal information on the rhythm of a target sequence or the timing of a planned hand movement. More specifically, the cerebellum seems to be crucial for synchronizing saccades with such learned or planned temporal events.

  • 278.
    Sailer, Uta
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Flanagan, J Randall
    Johansson, Roland
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Eye-hand coordination during learning of a novel visuomotor task.2005Inngår i: Journal of Neuroscience, ISSN 1529-2401, Vol. 25, nr 39, s. 8833-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigated how gaze behavior and eye-hand coordination change when subjects learned a challenging visuomotor task that required acquisition of a novel mapping between bimanual actions and their visual sensory consequences. By applying isometric forces and torques to a rigid tool held freely between the two hands, subjects learned to control a cursor on a computer screen to hit successively displayed targets as quickly as possible. The learning occurred in stages that could be distinguished by changes in performance (target-hit rate) as well as by gaze behavior and eye-hand coordination. In a first exploratory stage, the hit rate was consistently low, the cursor position varied widely, and gaze typically pursued the cursor. In a second skill acquisition stage, the hit rate improved rapidly, and gaze fixations began to mark predictively desired cursor positions, indicating that subjects started to program spatially congruent eye and hand motor commands. In a third skill refinement stage, performance continued to improve gradually, and gaze shifted directly toward the target. We suggest that during the exploratory stage, the learner attempts to establish basic mapping rules between manual actions and eye-movement commands. In this process, subjects may establish correlations between hand motor commands and their visual sensory consequences, primarily in fovea-anchored, gaze-centered coordinates, and correlations between recent hand motor commands and eye motor commands. The established mapping rules are then implemented and refined in the skill acquisition and refinement stages.

  • 279.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Eriksson, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Kompus, Kristiina
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Habib, Reza
    Southern Illinois University , Carbondale.
    Kauppi, Karolina
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Characterizing the neural correlates of modality-specific and modality-independent accessibility and availability signals in memory using partial-least squares2010Inngår i: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 52, nr 2, s. 686-698Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous studies have shown that information that currently cannot be retrieved but will be retrieved on a subsequent, more supported task (i.e. is available but not accessible) has a distinct neural signature compared with non-available information. For verbal paired-associates, an availability signal has been revealed in left middle temporal cortex, an area potentially involved in the storage of such information, raising the possibility that availability signals are expressed in modality-specific storage sites. In the present study subjects encoded pictures and sounds representing concrete objects. One day later, during fMRI scanning, a verbal cued-recall task was administrated followed by a post-scan recognition task. Items remembered on both tasks were classified as accessible; items not remembered on the first but on the second task were classified as available; and items not remembered on any of the tasks were classified as not available. Multivariate partial-least-squares analyses revealed a modality-independent accessibility network with dominant contributions of left inferior parietal cortex, left inferior frontal cortex, and left hippocampus. Additionally, a modality-specific availability network was identified which included increased activity in visual regions for available pictorial information and in auditory regions for available sound information. These findings show that availability in memory, at least in part, is characterized by systematic changes in brain activity in sensory regions whereas memory access reflects differential activity in a modality-independent, conceptual network, thus indicating qualitative differences between availability and accessibility in memory.

  • 280.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Eriksson, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Nilsson, Lars-Göran
    Stockholm University.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Age-related white matter microstructural differences partly mediate age-related decline in processing speed but not cognition2012Inngår i: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1822, nr 3, s. 408-415Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aging is associated with declining cognitive performance as well as structural changes in brain gray and white matter (WM). The WM deterioration contributes to a disconnection among distributed brain networks and may thus mediate age-related cognitive decline. The present diffusion tensor imaging (DTI) study investigated age-related differences in WM microstructure and their relation to cognition (episodic memory, visuospatial processing, fluency, and speed) in a large group of healthy subjects (n=287) covering 6 decades of the human life span. Age related decreases in fractional anisotropy (FA) and increases in mean diffusivity (MD) were observed across the entire WM skeleton as well as in specific WM tracts, supporting the WM degeneration hypothesis. The anterior section of the corpus callosum was more susceptible to aging compared to the posterior section, lending support to the anterior-posterior gradient of WM integrity in the corpus callosum. Finally, and of critical interest, WM integrity differences were found to mediate age-related reductions in processing speed but no significant mediation was found for episodic memory, visuospatial ability, or fluency. These findings suggest that compromised WM integrity is not a major contributing factor to declining cognitive performance in normal aging. This article is part of a Special Issue entitled: Imaging Brain Aging and Neurodegenerative disease.

  • 281.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Eriksson, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    Opposing effects of aging on large-scale brain systems for memory encoding and cognitive control2012Inngår i: Journal of Neuroscience, ISSN 0270-6474, E-ISSN 1529-2401, Vol. 32, nr 31, s. 10749-10757Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Episodic memory declines with advancing age. Neuroimaging studies have associated such decline to age-related changes in general cognitive-control networks as well as to changes in process-specific encoding or retrieval networks. To assess the specific influence of aging on encoding and retrieval processes and associated brain systems, it is vital to dissociate encoding and retrieval from each other and from shared cognitive-control processes. We used multivariate partial-least-squares to analyze functional magnetic resonance imaging data from a large population-based sample (n = 292, 25-80 years). The participants performed a face-name paired-associates task and an active baseline task. The analysis revealed two significant network patterns. The first reflected a process-general encoding-retrieval network that included frontoparietal cortices and posterior hippocampus. The second pattern dissociated encoding and retrieval networks. The anterior hippocampus was differentially engaged during encoding. Brain scores, representing whole-brain integrated measures of how strongly an individual recruited a brain network, were correlated with cognitive performance and chronological age. The scores from the general cognitive-control network correlated negatively with episodic memory performance and positively with age. The encoding brain scores, which strongly reflected hippocampal functioning, correlated positively with episodic memory performance and negatively with age. Univariate analyses confirmed that bilateral hippocampus showed the most pronounced activity reduction in older age, and brain structure analyses found that the activity reduction partly related to hippocampus atrophy. Collectively, these findings suggest that age-related structural brain changes underlie age-related reductions in the efficient recruitment of a process-specific encoding network, which cascades into upregulated recruitment of a general cognitive-control network.

  • 282.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Karolinska Inst, Aging Res Ctr, S-11330 Stockholm, Sweden; Stockholm Univ, S-11330 Stockholm, Sweden.
    Pudas, Sara
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI).
    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.
    Elevated hippocampal resting-state connectivity underlies deficient neurocognitive function in aging2014Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 111, nr 49, s. 17654-17659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The brain is not idle during rest. Functional MRI (fMRI) studies have identified several resting-state networks, including the default mode network (DMN), which contains a set of cortical regions that interact with a hippocampus (HC) subsystem. Age-related alterations in the functional architecture of the DMN and HC may influence memory functions and possibly constitute a sensitive biomarker of forthcoming memory deficits. However, the exact form of DMN-HC alterations in aging and concomitant memory deficits is largely unknown. Here, using both task and resting data from 339 participants (25-80 y old), we have demonstrated age-related decrements in resting-state functional connectivity across most parts of the DMN, except for the HC network for which age-related elevation of connectivity between left and right HC was found along with attenuated HC-cortical connectivity. Elevated HC connectivity at rest, which was partly accounted for by age-related decline in white matter integrity of the fornix, was associated with lower cross-sectional episodic memory performance and declining longitudinal memory performance over 20 y. Additionally, elevated HC connectivity at rest was associated with reduced HC neural recruitment and HC-cortical connectivity during active memory encoding, which suggests that strong HC connectivity restricts the degree to which the HC interacts with other brain regions during active memory processing revealed by task fMRI. Collectively, our findings suggest a model in which age-related disruption in cortico-hippocampal functional connectivity leads to a more functionally isolated HC at rest, which translates into aberrant hippocampal decoupling and deficits during mnemonic processing.

  • 283.
    Salami, Alireza
    et al.
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Aging Research Center, Karolinska Institutet and Stockholm University, SE-113 30, Stockholm, Sweden.
    Wåhlin, Anders
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Kaboodvand, Neda
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Aging Research Center, Karolinska Institutet and Stockholm University, SE-113 30, Stockholm, Sweden.
    Lundquist, Anders
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    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.
    Longitudinal Evidence for Dissociation of Anterior and Posterior MTL Resting-State Connectivity in Aging: Links to Perfusion and Memory2016Inngår i: Cerebral Cortex, ISSN 1047-3211, E-ISSN 1460-2199, Vol. 26, nr 10, s. 3953-3963Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neuroimaging studies of spontaneous signal fluctuations as measured by resting-state functional magnetic resonance imaging have revealed age-related alterations in the functional architecture of brain networks. One such network is located in the medial temporal lobe (MTL), showing structural and functional variations along the anterior-posterior axis. Past cross-sectional studies of MTL functional connectivity (FC) have yielded discrepant findings, likely reflecting the fact that specific MTL subregions are differentially affected in aging. Here, using longitudinal resting-state data from 198 participants, we investigated 5-year changes in FC of the anterior and posterior MTL. We found an opposite pattern, such that the degree of FC within the anterior MTL declined after age 60, whereas elevated FC within the posterior MTL was observed along with attenuated posterior MTL-cortical connectivity. A significant negative change-change relation was observed between episodic-memory decline and elevated FC in the posterior MTL. Additional analyses revealed age-related cerebral blood flow (CBF) increases in posterior MTL at the follow-up session, along with a positive relation of elevated FC and CBF, suggesting that elevated FC is a metabolically demanding alteration. Collectively, our findings indicate that elevated FC in posterior MTL along with increased local perfusion is a sign of brain aging that underlie episodic-memory decline.

  • 284. Salome, Nicolas
    et al.
    Haage, David
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Perrissoud, Daniel
    Moulin, Aline
    Demange, Luc
    Egecioglu, Emil
    Fehrentz, Jean-Alain
    Martinez, Jean
    Dickson, Suzanne L
    Anorexigenic and electrophysiological actions of novel ghrelin receptor (GHS-R1A) antagonists in rats2009Inngår i: European Journal of Pharmacology, ISSN 0014-2999, E-ISSN 1879-0712, Vol. 612, nr 1-3, s. 167-173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we provide the first pharmacological exploration of the impact of acute central nervous system exposure to three recently developed ghrelin receptor (GHS-R1A) ligands on food intake and on the electrical activity of the target cells for ghrelin in the hypothalamus. Central (i.c.v) injection of GHS-R1A antagonists to rats suppressed food intake induced by i.c.v ghrelin injection (1 mu g) in a dose-dependent manner with a total blockade at concentraions of 0.4 mu g and 8 mu g for JMV 3002 and JMV 2959 respectively. JMV 2810, a partial agonist, also suppressed ghrelin-induced food intake (range: 0.02-2 mu g). Moreover all three compounds reduced fasting-induced food intake in rats (i.e. the amount of food eaten during the first hour of food exposure after a 16 h fast). At the single cell level we also explored the effects of the compounds to suppress ghrelin (0.5 mu M)-induced changes in electrical activity of arcuate nucleus cells recorded extracellularly in a slice preparation. Preincubation followed by perfusion with the GHS-R1A ligands suppressed the responsiveness of arcuate cells to ghrelin. Thus, the recently developed GHS-R1A ligands (JMV 3002, 2959 and 2810) suppress ghrelin-induced and fasting-induced food intake at the level of the central nervous system. This appears to be mediated, at least in part, by a modulation of the activity of ghrelin-responsive arcuate nucleus cells. As the central ghrelin signalling system has emerged as an important pro-obesity target, it will be important to establish the efficacy of these GHS-R1A ligands to reduce fast mass in clincal studies.

  • 285.
    Sandström, Agneta
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin.
    Säll, R
    Peterson, Jonas
    Salami, Alireza
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Larsson, A
    Olsson, Tommy
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Medicin.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Brain activation patterns in major depressive disorder and job stress-related long-term sick leaveArtikkel i tidsskrift (Annet vitenskapelig)
  • 286.
    Sandström, Agneta
    et al.
    Remonthagen Stroke och hjärnskadecenter, Östersund.
    Säll, Roland
    Umeå universitet, Medicinska fakulteten, Institutionen för klinisk vetenskap, Psykiatri.
    Peterson, Jonas
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Medicin.
    Salami, Alireza
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Larsson, Anne
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Olsson, Tommy
    Umeå universitet, Medicinska fakulteten, Institutionen för folkhälsa och klinisk medicin, Medicin.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Brain activation patterns in major depressive disorder and work stress-related long-term sick leave among swedish females2012Inngår i: Stress, ISSN 1025-3890, E-ISSN 1607-8888, Vol. 15, nr 5, s. 503-513Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Deficits in executive and working-memory functioning associated with frontal lobe dysfunction are prominent in depression and work-related long-term sick leave (LTSL). This study used functional magnetic resonance imaging (fMRI) to investigate potential differences in brain activation patterns in these conditions. In addition, the function of the hypothalamic-pituitary-adrenal (HPA)-axis was examined and compared between groups. Since there is a clear overrepresentation of women in these diagnostic groups, and to ensure a more homogenous sample population, only women were included. To examine the neural correlates of relevant cognitive processes in patients on sick-leave > 90 days due to work-related LTSL, recently diagnosed patients with major depression (DSM-IV criteria, untreated), and healthy controls (n=10 each group), a 2-back working memory task and a visual long-term memory task were administered during fMRI scanning. HPA-axis functioning was investigated using a diurnal curve of saliva cortisol and a dexamethasone suppression test. Task performance was comparable among the three groups. Multivariate image analysis revealed that both memory tasks engaged a similar brain network in all three groups, including the prefrontal and parietal cortex. During the 2-back task, LTSL patients had significant frontal hypoactivation compared to controls and patients with depression. Saliva cortisol measurements showed a flattening of the diurnal rythmicity in LTSL patients compared to patients with depression and healthy contols. Taken together, these findings indicate that work stress-related LTSL and major depression are dissociable in terms of frontal activation and diurnal cortisol rhythmicity.

  • 287. Sasaki, Shigeto
    et al.
    Isa, Tadashi
    Pettersson, Lars-Gunnar
    Alstermark, Bror
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Fysiologi.
    Naito, Kimisato
    Yoshimura, Kazuya
    Seki, Kazuhiko
    Ohki, Yukari
    Dexterous finger movements in primate without monosynaptic corticomotoneuronal excitation.2004Inngår i: Journal of Neurophysiology, ISSN 0022-3077, Vol. 92, nr 5, s. 3142-7Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It is generally accepted that the precision grip and independent finger movements (IFMs) in monkey and man are controlled by the direct (monosynaptic) corticomotoneuronal (CM) pathway. This view is based on previous observations that pyramidotomy causes near permanent deficits of IFMs. However, in addition to the direct CM pathway, pyramidotomy interrupts several corticofugal connections to the brain stem and upper cervical segments. Indirect (oligosynaptic) CM pathways, which are phylogenetically older, have been considered to be of little or no importance in prehension. In three adult macaque monkeys, complete transection of the direct CM pathway was made in C4/C5, which is rostral to the forelimb segments (C6-Th1). Electrophysiological recordings revealed lack of the direct lateral corticospinal tract (LCST) volley, monosynaptic extracellular field potentials in the motor nuclei, and monosynaptic CM excitation. However, a disynaptic volley, disynaptic field potentials and disynaptic CM excitation mediated via C3-C4 propriospinal neurons remained after the lesion. Thus the lesion interrupted the monosynaptic CM pathway and oligosynaptic LCST pathways mediated by interneurons in the forelimb segments. Precision grip and IFMs were observed already after 1-28 days postoperatively. Weakness in force and deficits in preshaping remained for an observation period of 3 mo. Indirect CM pathways may be important for neuro-rehabilitation.

  • 288. Sasaki, Shigeto
    et al.
    Naito, Kimisato
    Yoshimura, Kazuya
    Isa, Tadashi
    Seki, Kazuhiko
    Pettersson, Lars-Gunnar
    Alstermark, Bror
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Ohki, Yukari
    Cortico-motoneuronal system and dexterous finger movements: reply2004Inngår i: Journal of Neurophysiology, ISSN 0022-3077, E-ISSN 1522-1598, Vol. 92, nr 6, s. 3601-3603Artikkel i tidsskrift (Fagfellevurdert)
  • 289.
    Schenker, Michael
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Burstedt, M K O
    Wiberg, Mikael
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Anatomi. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Handkirurgi.
    Johansson, Roland S
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Precision grip function after hand replantation and digital nerve injury.2006Inngår i: Journal of Plastic, Reconstructive & Aesthetic Surgery, ISSN 1748-6815, Vol. 59, nr 7, s. 706-716Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding how the loss of digital sensibility affects manual dexterity could have important implications for rehabilitation after hand injury. We investigated precision grip function during lifting tasks in seven patients after hand replantation, in five after single digital nerve injury and in four volunteers subjected to digital anaesthesia. Using their affected hand, all participants could successfully lift test objects with parallel and vertical grip surfaces and they all reliably increased the grip force with increasing object weight (0.11-0.55 kg). However, the grip forces used were frequently significantly higher than those applied by the unaffected hand. This was partly due to participants compensating for loss of sensibility with high grip force safety margins against slips, and partly related to misalignments of the fingertips on the grasp surfaces. The latter was most prominent after hand replantation. In a second series of lifting experiments we changed the shape of the grip surfaces in order to investigate the participants' ability to adapt grip forces based on tactile recognition of object shape. An important finding from this series was that in patients with poor clinical outcomes, the contralateral unaffected hand tended to mirror the abnormal grasp patterns of the injured hand. This suggests that control strategies developed for the impaired hand can influence the control of the contralateral uninjured hand.

  • 290. Schmitz, Christina
    et al.
    Jenmalm, Per
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Ehrsson, H Henrik
    Forssberg, Hans
    Brain activity during predictable and unpredictable weight changes when lifting objects.2005Inngår i: Journal of Neurophysiology, ISSN 0022-3077, Vol. 93, nr 3, s. 1498-509Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When humans repetitively lift the same object, the fingertip forces are targeted to the weight of the object. The anticipatory programming of the forces depends on sensorimotor memory representations that provide information on the object weight. In the present study, we investigate the neural substrates of these sensorimotor memory systems by recording the neural activity during predictable or unpredictable changes in the weight of an object in a lifting task. An unpredictable change in weight leads to erroneous programming of the fingertip forces. This triggers corrective mechanisms and an update of the sensorimotor memories. In the present fMRI study, healthy right-handed subjects repetitively lifted an object between right index finger and thumb. In the constant condition, which served as a control, the weight of the object remained constant (either 230 or 830 g). The weight alternated between 230 and 830 g during the regular condition and was irregularly changed between the two weights during the irregular condition. When we contrasted regular minus constant and irregular minus constant, we found activations in the right inferior frontal gyrus pars opercularis (area 44), the left parietal operculum and the right supramarginal gyrus. Furthermore, irregular was associated with stronger activation in the right inferior frontal cortex as compared with regular. Taken together, these results suggest that the updating of sensorimotor memory representations and the corrective reactions that occur when we manipulate different objects correspond to changes in synaptic activity in these fronto-parietal circuits.

  • 291.
    Scott, G
    et al.
    McGill University, Montréal and Université de Montréal.
    Westberg, Karl-Gunnar
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Vrentzos, N
    McGill University, Montréal.
    Kolta, A
    Université de Montréal.
    Lund, J P
    McGill University, Montréal and Université de Montréal.
    Effect of lidocaine and NMDA injections into the medial pontobulbar reticular formation on mastication evoked by cortical stimulation in anaesthetized rabbits2003Inngår i: European Journal of Neuroscience, ISSN 0953-816X, E-ISSN 1460-9568, Vol. 17, nr 10, s. 2156-2162Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neurons of the dorsal nucleus reticularis pontis caudalis (nPontc) fire rhythmically during fictive mastication, while neurons of the ventral half tend to fire tonically (Westberg et al., 2001). This paper describes the changes in the pattern of rhythmical mastication elicited by stimulation of the sensorimotor cortex during inhibition or excitation of neurons in this nucleus and adjacent parts of nucleus reticularis gigantocellularis (Rgc) in the anaesthetized rabbit. Masticatory movements and electromyographic (EMG) activity of the masseter and digastric muscles produced by cortical stimulation were recorded before, during and after injections of a local anaesthetic (lidocaine) or excitatory amino acid N-methyl-d-aspartate (NMDA) into nPontc and Rgc through a microsyringe with attached microelectrode to record neuronal activity. Lidocaine inhibited local neurons and modified the motor program, and the effects varied with the site of injection. Most injections into the ventral half of nPontc increased cycle duration, digastric burst duration and burst area. The action of lidocaine in dorsal nPontc was more variable, although burst duration and area were often decreased. The effects on the muscle activity were always bilateral. Lidocaine block of the rostromedial part of Rgc had no effect on movements or on EMGs. Injections of NMDA excited local neurons and when injected into ventral nPontc, it completely blocked mastication. Dorsal injections either had no effect or increased cycle frequency, while decreasing burst duration and area. No increases in EMG burst duration or area were observed with NMDA. Our findings suggest that neurons of ventral nPontc tonically inhibit other parts of the central pattern generator during mastication, while dorsal neurons have mixed effects. We incorporated these findings into a new model of the masticatory central pattern generator.

  • 292.
    Silfvenius, Herbert
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Projections to the cat cerebral cortex from fore- and hind limb group I muscle afferents1972Doktoravhandling, med artikler (Annet vitenskapelig)
  • 293.
    Sjöberg, Rickard L
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap, Klinisk neurovetenskap. University Hospital of Northern Sweden, Department of Neurosurgery, Umeå, Sweden.
    Stålnacke, Mattias
    Umeå universitet, Medicinska fakulteten, Institutionen för farmakologi och klinisk neurovetenskap.
    Andersson, Micael
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB).
    Eriksson, Johan
    Umeå universitet, Medicinska fakulteten, Umeå centrum för funktionell hjärnavbildning (UFBI). Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    The supplementary motor area syndrome and cognitive control2019Inngår i: Neuropsychologia, ISSN 0028-3932, E-ISSN 1873-3514, Vol. 129, s. 141-145Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Supplementary Motor Area (SMA)-syndrome is a transient disturbance of the ability to initiate voluntary motor and speech actions that will often occur immediately after neurosurgical resections in the dorsal superior frontal gyrus but will typically have disappeared after 3 months. The purpose of the present study was to investigate the extent to which this syndrome is associated with alterations in cognitive control. Five patients who were to different extents affected by the SMA-syndrome after surgery for WHO grade II gliomas in the left hemisphere, were tested with the color word interference (Stroop) test; the Bergen dichotic listening test and for letter and category verbal fluency before surgery, 1–2 days after surgery and approximately 3 months after surgery. Results suggest that the motor symptoms known as the SMA syndrome co-occur with pronounced deficits in cognitive control.

  • 294. Stein, L.
    et al.
    Bergdahl, M.
    Pettersen, K. S.
    Bergdahl, Jan
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Exploring the association between oral health literacy and alexithymia2015Inngår i: Community Dental Health, ISSN 0265-539X, Vol. 32, nr 3, s. 143-147Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low health literacy and alexithymia have separately been emphasized as barriers to patient-practitioner communication, but the association between the two concepts has not been explored. Objective: To test the hypothesis that low oral health literacy and alexithymia are associated. Method: Adults (n=127) aged 21-80 years (56% women) participated in this cross-sectional study. Oral health literacy was assessed using the interview-based Adult Health Literacy Instrument for Dentistry (AHLID) with scores from 1-5. The self-administered Toronto Alexithymia Scale (TAS-20) was used to assess three distinct TAS-20 factors and TAS-20 total score. Results: Significant negative correlations between AHLID scores and TAS-20 factors 2, 3 and TAS-20 total score were found. Regression analyses showed that TAS-20 factor 3, externally-oriented thinking (beta=-0.21, SE=0.02, p=0.017), and TAS-20 total score (beta=-0.18, SE=0.01, p=0.036) were significant predictors of AHLID level. Conclusion: The hypothesis that low oral health literacy is associated with alexithymia was supported. This finding proposes that alexithymia may be considered as a possible factor for low oral health literacy. However, the correlations are not strong, and the results should be regarded as a first step to provide evidence with additional research on this topic being needed.

  • 295.
    Stenvall, Michael
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Olofsson, Birgitta
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Lundström, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Englund, Undis
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Borssén, Bengt
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Svensson, Olle
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Gustafson, Yngve
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    A multidisciplinary, multifactorial intervention program reduces postoperative falls and injuries after femoral neck fracture.2007Inngår i: Osteoporosis International, ISSN 0937-941X, E-ISSN 1433-2965, Vol. 18, nr 2, s. 167-175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    INTRODUCTION: This study evaluates whether a postoperative multidisciplinary, intervention program, including systematic assessment and treatment of fall risk factors, active prevention, detection, and treatment of postoperative complications, could reduce inpatient falls and fall-related injuries after a femoral neck fracture.

    METHODS: A randomized, controlled trial at the orthopedic and geriatric departments at Umeå University Hospital, Sweden, included 199 patients with femoral neck fracture, aged >or=70 years.

    RESULTS: Twelve patients fell 18 times in the intervention group compared with 26 patients suffering 60 falls in the control group. Only one patient with dementia fell in the intervention group compared with 11 in the control group. The crude postoperative fall incidence rate was 6.29/1,000 days in the intervention group vs 16.28/1,000 days in the control group. The incidence rate ratio was 0.38 [95% confidence interval (CI): 0.20 - 0.76, p=0.006] for the total sample and 0.07 (95% CI: 0.01-0.57, p=0.013) among patients with dementia. There were no new fractures in the intervention group but four in the control group.

    CONCLUSION: A team applying comprehensive geriatric assessment and rehabilitation, including prevention, detection, and treatment of fall risk factors, can successfully prevent inpatient falls and injuries, even in patients with dementia.

  • 296.
    Stenvall, Michael
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Olofsson, Birgitta
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Lundström, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Svensson, Olle
    Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Gustafson, Yngve
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Inpatient falls and injuries in older patients treated for femoral neck fracture.2006Inngår i: Archives of gerontology and geriatrics (Print), ISSN 0167-4943, E-ISSN 1872-6976, Vol. 43, nr 3, s. 389-399Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A prospective inpatient study was performed at the Orthopedic and Geriatric Departments at the Umeå University Hospital, Sweden, to study inpatient falls, fall-related injuries, and risk factors for falls following femoral neck fracture surgery. Ninety-seven patients with femoral neck fracture aged 70 years or older were included, background characteristics, falls, injuries, and other postoperative complications were assessed and registered during the hospitalization. There were 60 postoperative falls among 26/97 patients (27%). The postoperative fall event rate was 16.3/1000 Days (95% CI 12.2-20.4). Thirty two percent of the falls resulted in injuries, 25% minor, and 7% serious ones. In multiple regression analyses, delirium after Day 7, HRR 4.62 (95% CI 1.24-16.37), male sex 3.92 (1.58-9.73), and sleeping disturbances 3.49 (1.24-9.86), were associated with inpatient falls. Forty-five percent of the patients were delirious the day they fell. Intervention programs, including prevention and treatment of delirium and sleeping disturbances, as well as better supervision of male patients, could be possible fall prevention strategies. Improvement of the quality of care and rehabilitation, with the focus on fall prevention based on these results, should be implemented in postoperative care of older people.

  • 297.
    Stenvall, Michael
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Olofsson, Birgitta
    Umeå universitet, Medicinska fakulteten, Institutionen för omvårdnad.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Lundström, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för omvårdnad.
    Gustafson, Yngve
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Bättre resultat med ett multidisciplinärt vårdprogram för äldre med höftfraktur2008Rapport (Annet vitenskapelig)
  • 298.
    Stenvall, Michael
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Olofsson, Birgitta
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik. Umeå universitet, Medicinska fakulteten, Institutionen för kirurgisk och perioperativ vetenskap, Ortopedi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Lundström, Maria
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Gustafson, Yngve
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Geriatrik.
    Improved performance in activities of daily living and mobility after a multidisciplinary postoperative rehabilitation in older people with femoral neck fracture: a randomized controlled trial with 1-year follow-up.2007Inngår i: Journal of Rehabilitation Medicine, ISSN 1650-1977, E-ISSN 1651-2081, Vol. 39, nr 3, s. 232-238Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    OBJECTIVE: To investigate the short- and long-term effects of a multidisciplinary postoperative rehabilitation programme in patients with femoral neck fracture.

    DESIGN AND SUBJECTS: A randomized controlled trial in patients (n = 199) with femoral neck fracture, aged >or= 70 years.

    METHODS: The primary outcomes were: living conditions, walking ability and activities of daily living performance on discharge, 4 and 12 months postoperatively. The intervention consisted of staff education, individualized care planning and rehabilitation, active prevention, detection and treatment of postoperative complications. The staff worked in teams to apply comprehensive geriatric assessment, management and rehabilitation. A geriatric team assessed those in the intervention group 4 months postoperatively, in order to detect and treat any complications. The control group followed conventional postoperative routines.

    RESULTS: Despite shorter hospitalization, significantly more people from the intervention group had regained independence in personal activities of daily living performance at the 4- and 12-month follow-ups; odds ratios (95% confidence interval (CI) ) 2.51 (1.00-6.30) and 3.49 (1.31-9.23), respectively. More patients in the intervention group had also regained the ability to walk independently indoors without walking aids by the end of the study period, odds ratio (95% confidence interval) 3.01 (1.18-7.61).

    CONCLUSION: A multidisciplinary postoperative intervention programme enhances activities of daily living performance and mobility after hip fracture, from both a short-term and long-term perspective.

  • 299.
    Stigsdotter Neely, Anna
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    A fronto-striatal workout to promote neuro-plasticity in old adults2013Inngår i: Psychophysiology, ISSN 0048-5772, E-ISSN 1469-8986, Vol. 50, nr Special issue, suppl. 1, s. S7-S8Artikkel i tidsskrift (Fagfellevurdert)
  • 300.
    Stigsdotter Neely, Anna
    et al.
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Sehlstedt, I
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Ekman, Urban
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Eriksson, Johan
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi. Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi.
    Sandberg, Petra
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Qwillbard, Tony
    Umeå universitet, Samhällsvetenskapliga fakulteten, Institutionen för psykologi.
    Nyberg, Lars
    Umeå universitet, Medicinska fakulteten, Institutionen för integrativ medicinsk biologi (IMB), Fysiologi. Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Diagnostisk radiologi.
    Working Memory Updating Training in Older Adults: Is Level of Performance After Training Related to Transfer?2013Inngår i: Journal of Psychophysiology, ISSN 0269-8803, E-ISSN 2151-2124, Vol. 27, nr Supplement 1, s. 69-70Artikkel i tidsskrift (Annet vitenskapelig)
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