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 chronic primary insomnia are better able to recall and/or recognize information from sleep onset intervals than good sleeper controls. Nine subjects participated in this pilot study, five of whom had a complaint of insomnia. The remaining four subjects were self-reported good sleeper controls. Subjects were matched for age, sex, and body mass. All subjects spent two nights in the sleep laboratory. The first night served as an adaptation night. The second night served as the experimental night during which a forced awakening and memory task was deployed. In this procedure, subjects were played single-word stimuli across four time periods: at natural sleep onset (Trial 1) and at the sleep onset transitions following three forced awakenings (Trials 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 memory for the word stimuli. The insomnia subjects, tended to identify more of the word stimuli on the recognition task (average for the four trials) and recognized significantly more of the words that were presented at sleep onset proper (Trial 1). This finding suggests that the natural mesograde amnesia of sleep may be attenuated in subjects with insomnia.

Temporal and stagewise distribution of high frequency EEG activity in patients with primary and secondary insomnia and in good sleeper controls.

In the present study, we evaluate the temporal and stagewise distribution of high frequency EEG activity (HFA) in primary and secondary insomnia. Three groups (n=9 per group) were compared: primary insomnia (PI), Insomnia secondary to major depression (MDD), and good sleeper controls (GS). Groups were matched for age, sex and body mass. Average spectral profiles were created for each sleep epoch. Grand averages were created for each NREM cycle and each stage of sleep after removing waking and movement epochs and epochs containing micro or miniarousals. It was found that HFA (in terms of relative power) tends to increase across NREM cycles, occurs maximally during stage 1 and during REM sleep, and that both these effects are exaggerated in patients with PI. In addition, HFA was found to be inversely associated with Delta activity and the three groups in our study appear to exhibit characteristic Delta/Beta patterns. Our data are consistent with the perspective that HFA is related to CNS arousal to the extent that Beta/Gamma activity occurs maximally during shallow stages of sleep and maximally in subjects with PI.

Beta/Gamma EEG activity in patients with primary and secondary insomnia and good sleeper controls.

STUDY OBJECTIVE: Several studies have shown that patients with insomnia exhibit elevated levels of Beta EEG activity (14-35 Hz) at or around sleep onset and during NREM sleep. In this study, we evaluated 1) the extent to which high frequency EEG activity is limited to the 14-32 Hz domain, 2) whether high frequency EEG activity (HFA) is associated with discrepancies between subjective and PSG measures of sleep continuity, and 3) the extent to which high frequency EEG activity occurs in patients with primary, as opposed to secondary, insomnia. DESIGN: Three groups (n=9 per group) were compared: Primary Insomnia, Insomnia secondary to Major Depression, and Good Sleeper Controls. Groups were matched for age, sex and body mass. Average spectral profiles were created for each NREM cycle after removing waking and movement epochs and epochs containing micro- or mini-arousals. SETTING: Sleep Research Laboratory PATIENTS OR PARTICIPANTS: Patients with primary and secondary insomnia INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: Subjects with Primary Insomnia exhibited more average NREM activity for Beta-1 (14-20Hz), Beta-2 (20-35Hz) and Gamma activity (35-45Hz) than the other two groups (p.<.01). Group differences were also suggestive for Omega activity (45.0-125Hz) (p.<.10), with MDD subjects tending to exhibit more activity than the other groups. Correlational analyses revealed that average NREM Beta-1 and Beta-2 activity tended to be negatively correlated with subjective-objective discrepancy measures for total sleep time and sleep latency. CONCLUSIONS: Our results confirm that Beta activity is increased in Primary Insomnia. In addition, our data suggest that high frequency activity in patients with Primary Insomnia is limited to the Beta/Gamma range (14-45 Hz), and is negatively associated with the perception of sleep.