INDUCTION OF VISUAL-IMAGERY DURING NREM SLEEP

In an attempt to induce eye movements (EMs) in non-rapid eye movement sleep, light and sound stimuli were presented to human subjects (at be low-waking threshold) during stage 2 sleep. EMs were used as an indica tor of ponto-geniculo-occipital (PGO) wave activity. When at least one concurrent EM in response to the stimuli was observed, the subjects w ere awakened and mentation reports collected. Compared to equivalent c ontrol periods with no stimulation, awakenings from the stage 2 stimul ation condition showed a higher frequency of visual imagery reports, e lectroencephalogram alpha activity, and k-complexes. Additional contro l and stimulation conditions elicited from rapid eye movement sleep aw akenings showed no significant differences in the frequency of visual imagery reports. When the amount of alpha activity before stage 2 awak enings from which imagery was reported was compared to that from which imagery was not reported, imagery awakenings showed significantly mor e alpha. Results can be interpreted as evidence for a link between PGO activity and dreaming in humans or in terms of an arousal-window hypo thesis of visual hallucinations.