EEG coherence changes between right and left motor cortical areas during voluntary muscular contraction

It is known that movements of the right side of the body are controlled by the left motor cortex of the brain. The aim of this study is to evaluate the contribution of right motor cortex of the brain in the central motor control of right-sided muscle contraction. EEG/EEG coherence analysis has been used to determine the functional coupling between the right and left motor cortical areas in twenty normal volunteers, during maximum voluntary contraction (MVC) and 50% MVC of right Adductor Pollicis muscle (APM). It shows that the maximum mean coherence values were: 0.751 during MVC at 10 and 12Hz, and 0.274 during 50% of MVC at 22 Hz. The minimum mean coherence values were: 0.716 during MVC at 48 and 50Hz, and 0.242 during 50% MVC at 34 Hz. The high coherence values obtained during MVC, and to a lesser extent during 50% of MVC, could be attributed to the need of recruitment of both motor cortical areas during the decision phase of central motor control of voluntary muscular contraction. The 'will' to perform maximum voluntary contraction could be a major factor, which contribute to the higher coherence values obtained during MVC than these associated with 50% of MVC.