University thesis:
Dissertation, Universität Freiburg, 2022
Footnote:
Description:
Abstract: Large-scale integration terms the mechanism which coordinates brain functions, presumably represented in spatially distant brain regions, to collectively produce other, higher brain functions. Aspects of special interest are the temporal dynamics of large-scale integration, which can be summarized as the chronnectome (Calhoun et al., 2014), and specifically the reconfiguration of movement-associated human brain networks. Furthermore, the fine tuning between cortical areas which are involved in movement planning and execution is not fully resolved.<br>Intracranial ECoG recordings offer a high spatial and temporal resolution and high signal to noise ratio, providing an excellent and unique source of high quality data to study dynamic processes in the human cortex.<br><br>In the present work, phase synchrony as a metric for functional connectivity was successfully applied to identify task related connectivity patterns during a naturally cued reach and grasping task. The thereby observed networks were assessed qualitatively and with tools originating in graph theory.<br><br>Network nodes and connections showed a characteristic distribution of their activity duration within an observation period and were therefore classified by either short- or long-lasting activity. Temporally stable activity was always accompanied by fluctuating activity, which appeared to be a basic mechanism in cortical control of voluntary reach and grasping movement. Connectivity unfolded between cortical areas known to be relevant for reach and grasping movements, involving somatosensory cortex, premotor cortex, primary motor cortex, inferior parietal cortex, Brodmann areas 44 and 45, prefrontal cortex and the parietal operculum.<br>Results from previous ECoG-based connectivity studies were thereby confirmed and complemented. The temporal reconfiguration of connectivity patterns and the involvement of specific cortical areas depended on the sequential events during the reach and grasping task.<br><br>The present findings revealed that connectivity patterns of the cortical areas generating voluntary reach and grasping movement consist of temporally stable alongside very dynamic activity. Connectivity patterns unfolded between postcentral and parietal cortex on the one hand and precentral, frontal and prefrontal cortex on the other hand. These configurations may be the basis for sustained coordination of cortical functions alongside quick adaption to<br>afferent information like visual, somatosensory and proprioceptive input. In conclusion, phase synchrony in the theta band (4-8 Hz) was identified as a probable mechanism of large scale integration during a naturally cued reach and grasping movement