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Circadian Rhythms in the Brain - A first step
Linköping University, Department of Biomedical Engineering. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
2013 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Circadian Rhythms (CR) are driven by a biological clock called as suprachiasmaticnucleus (SCN), located in a brain region called the hypothalamus. These rhythms are very much necessary in maintaining the sleep and wake cycle at appropriate times in a day. As a starting step towards non-invasive investigation of CR, aim is to study changes in the physiological processes of two Regions of Interest (ROI), the hypothalamus and the visual cortex. This was studied using a functional Magnetic Resonance Imaging (fMRI) technique to investigate for any changes or differences in the Blood Oxygen Level Dependent (BOLD)signals extracted from the ROI during a visual stimulation. We acquired and processed fMRI data to extract BOLD signals from ROI and the extracted signals are again further used to study the correlation with the experimental ON-OFF design paradigm.

The extracted BOLD signals varied a lot between the two specified brain regions within the same subject and between three types of fMRI data. These variations were found in terms of number of activated voxels and also Signal to Noise ratio(SNR) level present in the signals. The number of activated voxels and SNR werehigh in visual cortex whereas low number of activated voxels and low SNR were found in hypothalamus. The correlation between BOLD responses from primaryvisual cortex were shown as positive with the experimental stimulation whereas BOLD responses extracted from hypothalamus have shown a negative correlation in time with the experimental stimulation.

As a start up of the project, these BOLD responses can provide references for a future use in research studies, especially to further study about change in phase of the BOLD signal extracted exactly from the SCN. These phase responses can then be used to study physiological processing in subjects affected by sleep disorders.

Place, publisher, year, edition, pages
2013. , 96 p.
Keyword [en]
BOLD-fMRI, Circadian Rhythms, suprachiasmatic nucleus, sleep disorders, ROI, ON-OFF experimental paradigm, ICA, activated voxels, voxel time series BOLD responses, correlation analysis
National Category
URN: urn:nbn:se:liu:diva-89698ISRN: LiTH-IMT/MASTER-EX--13/022--SEOAI: diva2:608967
Subject / course
Master's Program Biomedical Engineering
2013-01-18, Wranne, Linköping University, Linköping, 13:15 (English)
Available from: 2013-03-04 Created: 2013-03-02 Last updated: 2013-03-04Bibliographically approved

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Dadi, Kamalaker Reddy
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Department of Biomedical EngineeringCenter for Medical Image Science and Visualization, CMIVThe Institute of Technology

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