Psychic state influences electrophysiological correlates of cognition

The number of white squares (5-10) of different spatial distribution, projected on a screen by means of a tachistosccope, had to be recognized by the subjects. Evoked potentials (EPs) were recorded from occipital skull at the midline. A computer technique was used for EPs classification into two groups according to objective correctness or incorrectness of the subject's answer, subjective certainty or uncertainty about the correctness of the subject's answer, correctness or intentional falsification of the answer, and for separate averaging of the groups of EPs. The amplitudes of late positive potentials of EPs were significantly larger for correct than for incorrect answers, for certain than uncertain judgements and for correct than for intentionally falsified answers (with the exception of highly elaborated false answers).