Changes in cortical negative DC shifts due to different motor task conditions

The experiments were performed to study the relationship between motor performance and DC potential curves recorded by scalp electrodes. Accordingly, we studied the influence of different movements (e.g., unilateral versus bilateral, simple versus complex, active versus passive, phasic versus tonic muscle activity) on negative DC potentials. Our results confirm that spatial distributions of DC potential maxima can be used as an indicator of the activation of distinct cortical areas. Furthermore, evidence is presented that some motor tasks have a greater influence on the magnitude of surface electronegativity than others. (1) Phasic muscle activity revealed a significantly larger potential size than tonic. (2) Performance of a complex finger movement task elicited an increased surface electronegativity compared with performance of a simple task. (3) No significant differences in potential size were found between left (untrained) and right (skilled) hand use during the performance of the same complex motor task. (4) This was also true for the performance of an active and a passive finger movement task, indicating that, at least in simple motor tasks, somatosensory afferents significantly contribute to the recorded potential curve.