IIIT Hyderabad Publications |
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Effects of structural perturbations on brain’s dynamics and the role of homeostatic plasticity in functional recoveryAuthor: Anirudh Nihalani Vattikonda Date: 2017-02-16 Report no: IIIT/TH/2017/20 Advisor:Dipanjan roy AbstractNeuroimaging methods like resting state fMRI and diffusion weighted tractography capture the large scale(macroscopic level) functional and structural connectivity between distant regions of the cortex. Using this data from healthy subjects, earlier studies have shown that structure and function are strongly correlated. In this thesis I have investigated the effects of structural perturbations on function and more importantly identified potential underlying neuronal mechanisms that are effected by such structural per-turbations. First we looked at how structure-function correlation of default mode network changes with age to gain insight into processes that might be responsible for cognitive and motor decline with ageing. Next using a bio-physically realistic computational model we investigated how focal lesions across cor-tex effect spontaneous neuronal dynamics. Computational modeling of the spontaneous dynamics over the whole brain provides critical insight into the spatio-temporal organization of brain dynamics at mul-tiple resolutions and their alteration to changes in brain structure (e.g. in diseased states, aging, across individuals). Recent experimental evidence further suggests that the adverse effect of lesions are visible on spontaneous dynamics characterized by changes in resting state functional connectivity and its graph theoretical properties (e.g. modularity). These changes originate from altered neuronal dynamics in individual brain areas that are otherwise poised towards a homeostatic equilibrium to maintain a stable excitatory and inhibitory activity. In this work, we employ a homeostatic inhibitory mechanism, balanc-ing excitation and inhibition in the local brain areas of the entire cortex under neurological impairments like lesions to understand global functional recovery (across brain networks and individuals). Previ-ous computational and empirical studies have demonstrated that the resting state functional connectivity varies primarily due to the location and specific topological characteristics of the lesion. We have shown that local homeostatic balance provides a functional recovery by re-establishing excitation-inhibition balance in all areas that are effected by lesion. We systematically compare the extent of recovery in the primary hub areas (e.g. default mode network (DMN), medial temporal lobe, medial prefrontal cortex) as well as other sensory areas like primary motor area, supplementary motor area, frontoparietal and temporo-parietal networks. Our findings suggest that stability and richness similar to the normal brain dynamics at rest is achievable by re-establishment of local excitation-inhibition balance. Full thesis: pdf Centre for Cognitive Science |
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