Community structure in large-scale cortical networks during motor acts

The purpose of the present work is to evaluate the community structure of the cortical network subserving the neurophysiologic processes in simple motor acts. To this end, we studied the topological properties of the functional brain connectivity in the frequency domain. The functional networks were estimated by means of the imaginary coherence from a dataset of high-resolution EEG recordings (4094 cortical sources) in a group of healthy subjects (n = 10) during a finger extension task. The analysis of the community structure was addressed through a particular detection algorithm that optimizes the modularity, a function related to the level of internal clustering inside the communities in the network. The principal results indicate that the cortical network changes its structural organization during the motor execution with respect to a baseline condition. Notably in the Beta band (12.5-30 Hz), the level of intra-module connectivity decreases, while inter-module connectivity increases reflecting the need for a neural integration of distant regions. Notably, this distributed interaction involves anatomical regions belonging to both the hemispheres including pre-motor and primary motor areas in the frontal and central part of the cortex as well as parietal associative regions, which are related to the planning, selection and execution of actions.