[Inversion of the polarity of contingent negative variation during falling asleep (author's transl)]

In 25 subjects repeated examination of contingent negative variation (S1 - S2 = 1 sec) under relatively unconstrained experimental conditions (simple, monotonous task, long recording sessions with eyes closed) favorized drowsiness and falling asleep. These periods of low vigilance level, observed in 7 subjects, are characterized by: (1) a global reduction in spontaneous EEG, measured by a diminution in the alpha/theta + delta index (FFT on bipolar leads P3--P4); (2) an inversion in alpha reactivity in the S1 - S2 interval, which, instead of diminishing, tends to augment 'paradoxically'; and (3) an inversion in the polarity of the CNV, which can reach a positive value as high as + 15 to + 20 microV. These electrophysiological phenomena are not accompanied by significant modifications in reaction time. The results are interpreted as the translation of an active 'internal inhibition' process, induced by repetition of monotonic stimuli. They are compared with animal data obtained by MARCZYNSKI and SHERRY (1972) and SKINNER and YINGLING (1977).