EEG correlates of wrist kinematics as revealed by averaging techniques and Morlet wavelet transforms.

The question regarding the invariant movement properties the central nervous system may organize to accomplish different motor task demands as reflected in EEG remains unsolved. Surprisingly, no systematic electrocortical research in humans has related movement preparation with different movement distance, although this area has been widely investigated in the field of motor control. This study examined whether the amplitude of discrete wrist movements influences the various EEG components both in time and frequency domains. Time-domain averaging techniques and Morlet wavelet transforms of EEG single trials were applied in order to extract three components [BP(0), N1, and LPS] of movement related potentials (MRP) and to quantify changes in oscillatory activity of the movement-induced EEG waveforms accompanying 20, 40, and 60 unilateral wrist flexion movements. The experimental manipulations induced systematic changes in BP(0) and N1 amplitude along the midline (Fz, Cz, and Pz) with 20 movement showing the most negativity and 60 the least. The dominant energy within a 30-50 frequency cluster from bilateral precentral (C3, Cz, C4), frontal (F3, Fz, F4), and parietal (P3, Pz, P4) areas with maximum at vertex (Cz) also appeared to be sensitive to movement amplitude with the least power observed during 60 wrist flexion. This suggests that movement amplitude may be a controllable variable that is highly related with task-specific cortical activation primarily at frontocentral areas as reflected in EEG.