The complementary relationship between wake and REM sleep in the oculomotor system: a negative finding.

INTRODUCTION. An inverse relationship between waking and REM sleep eye movements (EMS) has been found with respect to frequency, amplitude and direction of EMS (e.g., 1). Recently we found a significant decrease of rightward REMs after having increased rightward saccades during wake by means of a unilateral tachistoscopic visual test administered prior to sleep (2). This effect was specific for REMs of amplitude similar to those which were increased during wake; this allowed to exclude a oculomor muscles fatigue phenomenon, without clarifying the mechanisms underlying the effect (central or peripheral). Aim of the present study is to evaluate the role of automatically induced eye movements (i.e. optokinetic nystaginus -0KN-) in affecting direction and frequency of REMs during sleep, and to investigate the peripheral origin of complementary effect. METHOD.Ten Ss. were studied in 3 consecutive nights (1 adaptation, 1 baseline, 1 experimental). In the experimental night 5s. underwent 2 hours OKN stimulation at 15 deg/sec (5 Ss. had the stripes going leftward and the other 5 Ss. the stripes going rightward). Unipolar EEG (C3 and C4), EMC and bipolar vertical and horizontal EOG were recorded in AC. At the beginning of each recording session il calibration procedure utilizing EMS of known direction and amplitude permitted to establish the equivalency between voltage and degree of visual angle. EOG was scored visually by two experimenters who were blind with respect to the experimental condition. Any deflection of the pen greater than 3 deg and separated from another deflection by more than 300 msec. was considered to be an independent EM. hlininial velocity criteria were 100 deg/sec. Blinks, vertical EMS and other artifacts were not considered. Dependent variables were the direction of REMs and the total frequency of REMs (# of horizontal REMs/REM duration). RESULTSandCONCLUSlONS.The actual mean number of fast phases of nystagmus induced by the OKN stimulation was 12461.3 (1.7 fast phases/sec). No significant effect was found with regard to direction or frequency of REMs; other analyses considering the factor "REM cycle" also failed in showing any effect of complementary relationship between wake eye movements and REMs, suggesting that this relationship is specific for the saccadic system. Finally, the lack of any significant effect on stage 1 and 2 latency confirm and extend to night-time sleep the report of no effect of 10 min OKN stimulation on daytime sleepiness (3). OFTOKINETIC STlMULATlON IN WAKE DOES NOT AFFECT DIRECTION AND FREQUENCY OF EYE MOVEMEhI-S IN REhl SLEEP.