Selective modification of spontaneous ECoG rhythms of the cat somesthetic cortex by psychoactive drugs: behavioral correlates.

Three psychoactive drugs with known central effects were administered to the freely moving cat in order to study their action on spontaneous rhythmic activities recorded from the primary somesthetic cortex, which are analogous to the rolandic mu rhyhm in man. The ECoG patterns obtained are qualitatively identical to those of the normal subject, but their temporal organization is profoundly disturbed by the action of the drugs. The normal ECoG consists of three rhythmic systems with distinct frequencies and displays a considerable time variability. In contrast, psychoactive drugs induce a stabilized pattern with only one type (or at most two types) of rhythm prevailing for one or several hours, which never occurs under normal conditions. These ECoG rhythms underlie various behavioral states. Under d-amphetamine, correspondence remains excellent between behavior and ECoG; under Ditran, complete dissociation occurs; finally, LSD represents a borderline case in which ECoG and behavior are partially correlated and partially dissociated.