EEG RHYTHMS OF THE SENSORIMOTOR REGION DURING HAND MOVEMENTS

The aim of this study was to determine what motor behaviors or conditi ons were associated with an increased occurrence of beta activity in t he sensorimotor region of human subjects. EEG recordings were obtained from 8 electrodes symmetrically arranged around C3, with 3 cm interel ectrode spacing. The electrode montage allowed calculation of the Lapl acian operator at two positions, C3, and C3(c), overlying the hand are a of the motor cortex and of the somatosensory cortex, respectively A variety of tasks involving right-hand movements of different levels of complexity, attention and preparation were performed. The correspondi ng EEG power spectra were subsequently computed for frequencies betwee n 7 and 50 Hz. Repetitive hand movements alone (either drawing circles or writing one's signature) did not result in significantly increased beta activity in the sensorimotor region compared to relaxed conditio ns. However, both motor preparation and focused attention, whether mov ements were performed or not, were associated with an increase of high frequency beta activity (30-50 Hz) in the sensorimotor region. Theref ore, the facilitatory effect of attention and motor preparation and no t the functional activation of the sensorimotor cortex by hand movemen ts was associated with an increase in synchronized fast beta activity.