engKalthoff, DanielBlümich, BernhardFunctional connectivity of the rat brain in magnetic resonance imaginginfo:eu-repo/classification/ddc/540NMR-TomographieWistar-RatteRatteRatte <Gattung>GehirnHirnforschungSchlaganfallNeurologieKöln / Max-Planck-Institut für Neurologische ForschungNMR-BildgebungBildgebendes VerfahrenMolekulare BildgebungNeurowissenschaftenChemieBOLDfunktionelle KonnektivitätKonnektivitätfunctional connectivityconnectivityresting statersfMRIINTRODUCTION: Functional connectivity – generally defined by Friston as “temporal correlation of a neurophysiological index measured in different brain areas” – was first reported for human functional magnetic resonance imaging (fMRI) of the brain by Biswal and co-workers in 1995. It relies on spontaneous low frequency fluctuations (< 0.1 Hz) of the blood oxygenation level dependent (BOLD) signal that are synchronized in distant brain regions in the absence of any task or stimulus, hence the term “resting state". These low frequency BOLD fluctuations are believed to reflect spontaneous neuronal activity.MOTIVATION: During the last 15 years, functional connectivity and related concepts have proven their high sensitivity in human psychiatric and neurological disorders, among them Alzheimer's and Parkinson's disease, depression and stroke. In this scenario, functional connectivity measured by MRI (fcMRI) may provide an important bridge between clinical research and basic neuroscience.OBJECTIVE: The present work aimed at establishing resting state functional MRI (rsfMRI) and related measures of functional connectivity for high-field MR imaging of the rat brain. The in vivo assessment of MRI based parameters - both structural and functional - has a long history at the Max Planck Institute in Cologne, particularly in application to stroke. Thus, the objective was furthermore to investigate the potential of rsfMRI and functional connectivity for longitudinal studies of stroke and recovery. RESULTS: During the course of this work, a protocol for assessment of rat brain functional connectivity by MRI (fcMRI) was successfully established for high-field imaging. An fMRI protocol previously established in this laboratory was advanced for non-invasive and longitudinal acquisition of rsfMRI data and a comprehensive data analysis package was compiled for pre-processing and assessment of functional connectivity measures. Resting state low frequency fluctuations underlying functional connectivity were specifically examined for non-neuronal sources of variance. We found that respiratory related physiological noise at high field has a dramatic impact on functional connectivity measures and proposed a correction scheme based on regression of physiological nuisance variables. Furthermore, we examined rat brain functional connectivity in different anaesthetic regimes employing seed correlation along with the exploration of functional connectivity networks using independent component analysis (ICA). We found that our established protocol of Medetomidine sedation outperformed conventional Isoflurane anaesthesia with respect to complexity and level of detail of functional connectivity networks. At last, the established protocol was applied to a rat model of stroke in a pilot study. Functional connectivity and activation measures were assessed before and at five weeks after stroke. Analysis of this data revealed a number of valuable impulses and implications for future investigations of connectivity in stroke and recovery.CONCLUSION: The present work has put forth a well-characterised, ready-to-use protocol for fcMRI that will be employed in the near future to characterise functional recovery from stroke.Aachen : Publikationsserver der RWTH Aachen University IV, 173 S. : Ill., graph. Darst. (2011). = Aachen, Techn. Hochsch., Diss., 2011info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionPublikationsserver der RWTH Aachen University2011info:eu-repo/semantics/openAccessDEhttps://publications.rwth-aachen.de/record/82736https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-143109%22StudentsStudent Financial Aid ProvidersTeachersResearchersinfo:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:82-opus-39440