K-COMPLEXES - ARE THEY SIGNS OF AROUSAL OR SLEEP PROTECTIVE

The number of K-complexes recorded at the central-temporal EEG derivat ion (C3-T3) during 5 min periods for both the ascending and descending phase of Stage 2 of NREM sleep for cycles 1, 2... etc, were counted i n 10 subjects for each of the following five groups: normal persons, p atients with a primary generalized form of epilepsy, narcolepsy, insom nia and obstructive sleep apnoea. The differences in time spent in dif ferent stages of sleep were as expected for these types of patients. A 2-within, 1-between factors, repeated measure ANOVA was applied to th e data on K-complexes. Overall, there was no significant difference be tween the number of K-complexes observed during the ascending and desc ending phases of the different sleep cycles. Patients with a sleep dis order had significantly less well-defined K-complexes than the normals and the patients with a primary form of generalized epilepsy: for ins omnia (P=0.035), for apnoea (P=0.011) and for narcolepsy (P=0.001). Th ere was a significant, but very low correlation coefficient between th e number of K-complexes observed during Stage 2 of NREM sleep and the time spent during that stage for all groups combined (Rho 0.27, P=0.00 2) and for the narcoleptic patients (Rho 0.44, P=0.017). In all, the f indings lend support to the hypothesis that a K-complex can be seen as a 'defensive response', or has a sleep protective function.