Changes of slow cortical negative DC-potentials during the acquisition of a complex finger motor task.

To study whether electrophysiological correlates of increasing motor skill can be demonstrated in man, we recorded cortical negative DC-potentials during the acquisition of a complex finger movement in 21 subjects. The movement consisted in moving a matchstick to and fro between the index finger (II) and the little finger (V). Cortical negative DC-potentials were recorded at Fz, Cz, C1, C2 and Pz. As a control a simple finger movement was performed during the same session by 7 of the Ss. Both tasks were repeated 60-80 times and averages of the first and the last 15 artifact-free single runs were compared. Whereas only a slight, inconstant decrease in surface electronegativity during the simple motor task was observed, a significant reduction in potential size occurred during the complex task at Cz (maximum), C1, C2 and Pz but not at Fz. In addition, a significant difference in the decrease of surface electronegativity between various electrode positions was observed. We suggest that these changes in potential size during the process of motor learning may reflect an altered cortical organisation of movement control during the acquisition of a complex motor task.