MESOGRADE AMNESIA DURING THE SLEEP ONSET TRANSITION - REPLICATION ANDELECTROPHYSIOLOGICAL CORRELATES

The present study was designed to explore mechanisms of amnesia for me aningful auditory material presented during the sleep onset transition . Thirty undergraduate subjects (17 female, 13 male) were presented wi th auditory stimuli in an oddball paradigm until sleep onset. Subjects were allowed to accumulate either 30 seconds or 10 minutes of sleep, then awakened and tested on free recall and recognition memory for the meaningful stimuli. After 10 minutes of sleep, but not after 30 secon ds of sleep, subjects had profound amnesia on free recall for stimuli presented in the 4-minute window prior to sleep onset. Increased beta electroencephalograph (EEG) power during the sleep period correlated p ositively with recall of stimuli in the 4-minute presleep window. Even t-related potential recordings provided suggestive evidence that subje cts continued to process the auditory stimuli to some extent during th e sleep onset transition. When allowed to sleep for 10 minutes, subjec ts evidenced a mixed anterograde and retrograde amnesia for auditory s timuli presented in the 4-minute window prior to sleep onset. The resu lts are discussed in terms of stimulus encoding, consolidation, and re trieval.