An abnormal type of electroencephalographic response (positive bursts) confined to the posterior association cortex is found in patients with episodic psychopathic behavior when they are subjected to auditory stimulation during sleep. Similar results are found in animals when cortical activity is topically blocked with depressant drugs, and in other states of depressed cortical activity. It is suggested that the positive bursts are sleep spindles altered by blocking of activity in the superficial layers of the association cortex. That this may be due to delayed maturation of this region in these subjects is further suggested by the higher incidence of these bursts in younger people. From this it is postulated that the clinical manifestations are release phenomena due to transient cortical blocking of inhibitory mechanisms in the association cortex rather than the result of subcortical epileptic discharges.