Investigating the modulation of brain activity associated with handgrip force and fatigue.

OBJECTIVE To investigate the effect of force level and fatigue on brain activity during handgrip tasks. METHODS Electroencephalography (EEG) signals were recorded from eleven healthy male subjects when they performed 25%, 50% and 75% maximal voluntary contraction (MVC), and were in fatigue state. EEG powers in different handgrip tasks were analyzed in the frequency domain and time domain respectively. RESULTS The EEG power at 25%MVC was significantly lower than that at 75%MVC in gamma band (p< 0.05) for electrode C3, C4, Cz, Pz and Fz. EEG power at 25%MVC was also significantly lower than that at 75%MVC in beta band (p< 0.05) for electrode C3. However, the handgrip force level and fatigue did not affect the EEG powers for the other frequencies and electrodes (p> 0.05). CONCLUSION The results suggest that handgrip force level may modulate the brain activity in certain frequency bands and cortical regions. EEG power is a useful tool to characterize the motor state.