Cortical connectivity during isometric contraction with concurrent visual processing by partial directed coherence

Previously, coherence function has been applied to investigate the effects of external visual stimulation on cortico- muscular synchronization. It was proven that brain regions with enhanced 8-12 Hz (alpha)/decreased 31-50 Hz (gamma) power have strong coupling between them and demonstrated as codes of brain functional activity. However, the cortical connectivity was performed using ordinary coherence that does not provide the directional flow of information in the brain. In this paper, cortical directional connectivity in the brain was investigated by adopting partial directed coherence method. Two tasks were investigated, i.e. Control and Count Visual Stimuli tasks. The Control task required subject to maintain first dorsal interosseous muscle contraction without visual stimulation. In Count Visual task, the subject was asked to count certain stimuli in a random series of visual stimuli displayed on a screen while maintained the muscle contraction. Result showed that in control task, most of the sources of the information pathways were from the frontal region. In count visual task, most of the sources of the information pathways came from the occipital, temporal and parietal regions and ended at the central or frontal regions. These results provide information on the cortical functional connectivity during motor action with competing visual processing. As conclusion, frontal region provides the source of information during motor task alone while the sources of information come from occipital, temporal and parietal regions for the concurrent motor task with competing visual processing