EFFECTS OF STIMULUS-INTENSITY ON ELICITED PONTOGENICULOOCCIPITAL WAVES

Waves similar to spontaneous ponto-geniculo-occipital (PGO) waves of paradoxical sleep (PS) in cats are elicited by tones and can be considered a form of evoked potential termed PGO(E). The aims of the present experiment were to determine: (1) the effects of tone intensity on the probability of producing PGO(E); (2) the effects of intensity on the amplitude and latency of PGO(E) across slow-wave sleep (SWS) and PS; (3) whether the effects of intensity on PGO(E) are similar to those on a particular form of auditory evoked potential known as the mid-latency response (MLR). Increasing the intensity of the stimulus from 60 to 100 in 10 dB increments resulted in increased probability, increased amplitude, and decreased latency of PGO(E) in both SWS and PS. This pattern was similar to published findings with MLR, and latencies of PGO(E) (roughly 60-100 msec) fell within the range of 'C wave' type of MLR recorded in intralaminar nuclei of the thalamus of cats. The possibility that PGO(E) and MLR share underlying mechanisms and represent the same phenomenon is discussed with particular attention to the function of the mechanisms during alerting and orienting.