Desynchronization in Speech and Non-speech
Orofacial Movements: the Effects of Task Complexity
P Tremblay, V Gracco
Oscillatory cortical activity in the beta frequency range (14-32 Hz) for externally-paced speech and non-speech oral movements (lip protrusion) was investigated in ten right-handed healthy volunteers. Electroencephalographic (EEG) activity was recorded from the scalp and the magnitude, timing, and lateralization of the event-related desynchronization (ERD) for the two tasks was compared. In contrast to a recent study reporting no significant speech and non-speech differences in ERD, we found significant differences in a number of ERD measures. The amplitude and duration of the ERD was larger and longer for speech than for lip protrusion. The maximal ERD decrease occurred slightly before the onset of EMG for lip protrusion but occurred well after the onset of EMG for speech. No strong evidence of lateralization was noted. However, the latency of the maximum ERD over the left and right side recording sites was highly correlated for speech but completely uncorrelated for lip protrusion. We also found a number of gender differences that have not previously been reported.