Sleep's Influence on a Reflexive Form of Memory That Does Not Require Voluntary Attention

Study Objectives: Studies to date have examined the influence of sleep on forms of memory that require voluntary attention. The authors examine the influence of sleep on a form of memory that is acquired by passive viewing. Design: Induction of the McCollough effect, and measurement of perceptual color bias before and after induction, and before and after intervening sleep, wake, or visual deprivation. Setting: Sound-attenuated sleep research room. Participants: 13 healthy volunteers (mean age = 23 years; age range = 18-31 years) with normal or corrected-to-normal vision. Interventions: N/A. Measurements and Results:) Encoding: sleep preceded adaptation. On separate nights, each participant slept for an average of 0 (wake), 1, 2, 4, or 7 hr (complete sleep). Upon awakening, the participant's baseline perceptual color bias was measured. Then, he or she viewed an adapter consisting of alternating red/horizontal and green/vertical gratings for 5 min. Color bias was remeasured. The strength of the aftereffect is the postadaptation color bias relative to baseline. A strong orientation contingent color aftereffect was observed in all participants, but total sleep duration (TSD) prior to the adaptation did not modulate aftereffect strength. Further, prior sleep provided no benefit over prior wake. Retention: sleep followed adaptation. The procedure was similar except that adaptation preceded sleep. Postadaptation sleep, irrespective of its duration (1, 3, 5, or 7 hr), arrested aftereffect decay. By contrast, aftereffect decay was arrested during subsequent wake only if the adapted eye was visually deprived. Conclusions: Sleep as well as passive sensory deprivation enables the retention of a color aftereffect. Sleep shelters this reflexive form of memory in a manner akin to preventing sensory interference.