ERPS and spontaneus fluctuations in the quality of sleep in insomniacs and good sleepers

Previous results [1,2] show that in primary insomniacs P300 amplitude is significantly higher compared to good sleepers only with the occurrence of a bad night. These results suggest a relationship between cortical arousal and spontaneus fluctuations of the quality of sleep in insomniacs. Aim of the present study was to deeply investigate this relationship considering also earlier ERPs components related to basic level of arousal [3]. 11 primary insomniacs and 11 healty matched controls were actigraphically monitored for 1 week. At their homes, each day, before and after sleep, subjects filled in a diary and their N1, P2 and P300 ERPs (oddball paradigm) were recorded through portable equipment. For each subject diary and actigraphic data were used for identifying the worse (N) and the best (N1) sleep quality night in the week. The mean amplitudes of the N1 and the P300 from FZ, CZ and PZ of both groups were submitted to separate ANOVAs considering NIGHT (N versus N1), GROUP (insomniacs versus controls), TIME of day (presleep versus postsleep) and LEAD (Fz versus CZ versus Pz.) as factors. ANOVA on N1 amplitude showed a significant GROUP X TIME X LEAD interaction (F (2,40)53,61; Po0.04). Post Hoc Test indicates that N1 amplitude recorded from FZ is significantly higher in insomniacs compared to controls both in the evenings before the N and in the evening before the N1. ANOVA on P300 amplitude shows a significant GROUP X NIGHTX LEAD interaction (F (2,40)53,16; Po0.05). Post hoc Test indicates that in insomniacs P300 amplitude recorded from FZ is significantly higher compared to controls, only with the occurrence of the N. The relationship between ERPs amplitude and spontaneous fluctuations in sleep quality of primary insomniacs occurs for late but not for early ERPs components.