The mesograde amnesia of sleep may be attenuated in subjects with primary insomnia

In this study, we pilot tested one of the more controversial components of the Neurocognitive Model of Insomnia; the proposition that subjects with ch ronic primary insomnia are better able to recall and/or recognize informati on from sleep onset intervals than good sleeper controls. Nine subjects par ticipated in this pilot study, five of whom had a complaint of insomnia. Th e remaining four subjects were self-reported good sleeper controls. Subject s were matched for age, sex, and body mass. All subjects spent two nights i n the sleep laboratory. The first night served as an adaptation night. The second night served as the experimental night during which a forced awakeni ng and memory task was deployed. In this procedure, subjects were played si ngle-word stimuli across four time periods: at natural sleep onset (Trial 1 ) and at the sleep onset transitions following three forced awakenings (Tri als 2-4 from Stage 2 sleep). All subjects were awakened after about 6 h had elapsed from lights out and were tested for free recall and recognition me mory for the word stimuli. The insomnia subjects, tended to identify more o f the word stimuli on the recognition task (average for the four trials) an d recognized significantly more of the words that were presented at sleep o nset proper (Trial 1). This finding suggests that the natural mesograde amn esia of sleep may be attenuated in subjects with insomnia. (C) 2001 Elsevie r Science Inc. All rights reserved.