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

In the present study, we evaluate the temporal and stagewise distribution o f high frequency EEG activity (HFA) in primary and secondary insomnia. Thre e groups (n = 9 per group) were compared: primary insomnia (PI). Insomnia s econdary to major depression (MDD), and good sleeper controls (GS). Groups were matched for age, sex and body mass. Average spectral profiles were cre ated for each sleep epoch. Grand averages were created for each NREM cycle and each stage of sleep after removing waking and movement epochs and epoch s containing micro or miniarousals. It was found that HFA (in terms of rela tive power) tends to increase across NREM cycles. occurs maximally during s tage 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 wi th Delta activity and the three groups in our study appear to exhibit chara cteristic 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 w ith PI.