Functional Compartmentation and Connectivity of the Basal Ganglia at 9.4 Tesla

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Subcortical structures of the human brain comprise a large number of different nuclei, which account for about 25% of the total brain volume. The largest nuclei are assembled in the basal ganglia (BG) and the thalamus (Th), which both possess a relatively homogeneous anatomical structure, although they are in cooperation with various cortical areas responsible for a variety of functions. For example the four major nuclei of the BG, the caudate nucleus (NC), putamen (PU), and the internal (GPi) and external part (GPe) of the globus pallidum (GP) are involved in reinforcement learning, selection, processing, and control of motor commands, in limbic reactions, as well as in the inhibition of undesired actions. Thus, the proper interplay between the BG, cortex, and thalamus are fundamental for human behavior. Therefore, a better understanding of how the different nuclei of the BG and the Th work in concert with the cortex is urgently required. Moreover, such knowledge is of utmost importance to explain how neurological, neurodegenerative and psychiatric disorders alter brain function. Thus, our primary goal is to deliver a functional atlas of the BG to enhance the understanding of how these structures work together.We, therefore, want to investigate the segregated and integrative functional areas of the human BG and the Th and to determine their connectivity profiles with the cortex by applying high-resolution MRI at 9.4 Tesla. As the increased signal/noise at high-field MRI at 9.4 Tesla offers a superior spatial and temporal resolution, we hope to identify functional subunit within these nuclei. Using dedicated T1- and T2-weighted sequences and quantitative susceptibility maps we aim to: a) assess the anatomical delineation of the four nuclei of the BG, b) perform high-resolution (< 1 mm3) resting state (rs-fMRI) and task-related functional MRI (task-fMRI) measurements in groups of healthy controls, c) identify functional subunits within these nuclei, and d) analyze their connectivity patterns to i) cortical areas and ii) to different subunits of the thalamus. Finally, we plan to analyze iii) whether an overall correspondence and consistency exist between these structures at rest and during different task conditions. We hypothesize the existence of a reliable and reproducible functional parcellation of the BG, which can be identified via high-resolution imaging. Furthermore, we expect that parcellation and connectivity will differ between rest and task as it is influenced by the ongoing motor, somatosensory, and limbic processing.