The Effects of Slow Cortical Potentials on Response Speed

The relationship between slow cortical potentials (SCPs) and response speed was investigated by training subjects to induce different cortical shifts by means of a biofeedback procedure. During two identical experimental sessions trials with visual feedback of the actual DC-shifts alternated with reaction time trials without feedback. In reaction time trials only the signal for the required change in polarity was provided. At the end of the signal interval an immediate button-press was required to stop a hissing noise. Two groups of 10 subjects each were investigated, one group receiving feed back from the left precentral recording(C₃) and the other from the right precentral recording (C₄). Results showed that subjects achieved control over their SCPs. At the end of the training period in the second session significant differences in SCPs between trials of the different required polarities were observed, during feedback trials as well as during reaction time trials without feedback. Subjects responded faster during trials in which a change toward more cortical negativity was required as compared to trials requiring less negativity.