RESPIRATORY-LIKE PERIODICITIES IN SLOW EYE-MOVEMENTS DURING SLEEP ONSET

Slow eye movements (SEMs) during sleep onset and their relationship to vegetative rhythms were investigated in six healthy, sleep-deprived s ubjects, yielding 143-289 SEMs in an epoch of 31.5-56 min per experime nt. Exclusively, sleep in stages I and II was recorded. From the bandp ass-filtered electro-oculogram (EOG) signal (cut-off frequencies 0.05 and 1 Hz), turning points of the gaze were detected and compared with the start of inspiration, which was discriminated from the abdominal r espiratory excursions. SEM cycle times varied considerably more than r espiratory cycle times (P < 0.05 in Levene's test). Both were preferen tially of equal length, or, in some subjects, in 2:1 co-ordination. Cr oss-correlation histograms yielded that inspiration and SEMs were also temporally co-ordinated. Thus, there is a temporal coherence regardin g the occurrence, the cycle time and the phase between SEMs and a resp iratory-like rhythm. Our findings show that it is not exactly the resp iratory rhythm that is mirrored in the SEMs. Rather, we favour the int erpretation of an autorhythmicity that is temporarily connected to the common brainstem system in the reticular formation of the brainstem.