Observations on Photically Evoked Occipital and Vertex Waves during Sleep in Man.

Information about the character of the visual evoked response in man during sleep and possible differences between waking and sleep is as yet limited. Vanzulli et a2. (1960) reported that response latencies were increased and “positive waves” augmented. CigLnek ( 1961 ) noted that the early triphasic complex was unchanged except for increased latency while a later wave (“V”) was increased in amplitude, broadened and delayed. He observed typical K-complexes during deep sleep. Guillard (1960) has reported that an anteriorly distributed response may persist in sleep when the posterior response has disappeared. He also reported longer response latency as depth of sleep increased. Brazier (1960) and Barlow (1960) have averaged occipital responses to flash in a subject both awake and asleep and have shown that periodic alpha range oscillations may disappear during sleep. The present communication describes morphological characteristics of cerebral responses evoked by single intense photic stimuli presented during sleep, compares these characteristics with those observed in waking and relates response morphology to electrographic and behavioral measures of level of consciousness. Attention is also given to topographical features of the responses, particularly in relation to distinctions that may be drawn between central and occipital events.