The polysomnogram and electrocardiogram were continuouslyrecorded before lights out until the termination of the firstREM sleep in 14 young healthy subjects. The subject remainedin a semirecumbent posture in dim light during waking periodbefore light out. The effects of circadian rhythm were controlled.Heart rate variability was calculated using the MemCalc methodfrom electrocardiogram R–R intervals. The heart rate variabilitywas analyzed in time course changes before and after sleep onset.The LF/(LF+HF) and LF/HF declined clearly prior 30 min tosleep onset. The HF increased prior to sleep onset in consecutivephases. The change of LF/(LF+HF) and LF/HF preceded slowwave sleep and REM sleep. There was no clear stage dependencyafter sleep onset in HF. The results mentioned above suggest thatthe cardiac sympathetic nervous activity represented LF/(LF+HF) and LF/HF may possibly anticipate sleep and eachsleep stage onset.

doi:10.1016/j.clinph.2007.05.057

47. Sleep

Preliminary evaluation of cyclic alternating pattern (CAP) in

Japanese insomniac patients—T. Yagi 1, M. Ozone 2, S.

Chiba 1, Y. Inoue 3, H. Itoh 2, M. Sasaki 1, T. Shimizu 4,

M.G. Terzano 5 (1 Ota Memorial Sleep Center, Kanagawa,Japan, 2 The Jikei University, Tokyo, Japan, 3 Japan

Somnology Center, Neuropsychiatric Research Institute,

Tokyo, Japan, 4 Akita University, Akita, Japan, 5 Univer-

sity of Parma, Parma, Italy)

The cyclic alternating pattern (CAP) is a periodic EEGactivity during non-REM sleep that may relate to subjectivesleep quality and signify sleep instability and/or sleep distur-bance. To evaluate the usefulness of CAP in Japanese insom-niac patients, nine patients with psychophysiological insomnia(four males and five females; 41.9 ± 12.8 years) and ,for com-parison, eight age- and gender-matched control subjects (fourmales and four females; 46.3 ± 12.3 years) without any sleepcomplaints were enrolled in the study. Nocturnal polysomnog-raphy (PSG) were performed in air-conditioned, light- andnoise-controlled sleep laboratory. Conventional PSG parame-ters and CAP parameters were quantified by experienced scor-ers. Visual analogue scale showed that insomnia subjectsranked lower quality of sleep than control subjects. Amongconventional parameters, only wake time after sleep onsetand sleep efficiency showed significant differences between two

groups. However, CAP parameters could clearly distinguishedinsomnia group from control group, indicating the increase inCAP rate (66.8 ± 7.75% vs. 38.0 ± 7.75%), CAP time(171 ± 37.7 min vs. 117 ± 21.0 min), and the numbers of CAPcycles (408 ± 108 vs. 259 ± 67.2), respectively. These resultssuggest that CAP parameters were more useful indicators toassess sleep disturbance of insomniac patients than conven-tional PSG parameters.

doi:10.1016/j.clinph.2007.05.058

48. Sleep

Subjective sleep duration was not related with sleep durationbut with wake duration in healthy male volunteers—H.

Tagaya 1, M. Uchiyama 1, Y. Kamei 2, K. Shibui 1, A.

Ozaki 1, X. Tan 1, H. Suzuki 1, S. Okada-Aritake 1, L. Li 1

(1 Department of Psychophysiology, National Institute of

Mental Health, National Center of Neurology and Psychi-

atry, Japan, 2 Department of Psychiatry, Kohnodai Hospi-

tal, National Center of Neurology and Psychiatry, Japan)

We investigated subjective sleep duration (SSD) under highsleep pressure condition (HS) and low sleep pressure condition(LS). Seven healthy male volunteers aged 22.4 ± 0.79 years partic-ipated. Written informed consents were obtained. Polysomno-gram (PSG) have recorded for 9 h between 1200 and 2100 hafter 28-h sleep deprivation (HS) and after recovery sleep (LS).PSGs were separated into six 90-min period. Subjects were wokenonce in every period during sleep stage 2, and were asked SSD ofthe preceding sleep.

Forty-one periods in HS and 38 periods in LS contained atleast one epoch of sleep. Objective sleep parameters did not differbetween HS and LS except time spent awake which was signifi-cantly longer in LS. SSD was significantly longer than objectivesleep duration (OSD), and were significantly shorter in LS.Among all the periods with sleep, SSD was negatively correlatedwith time spent awake. No correlation was found between SSDand OSD. Our results suggested that we estimate our sleep dura-tion by subtracting wake duration from time spent in bed, insteadof perceiving sleep duration directly. This may provide an expla-nation for effectiveness of stimulus control therapy, whichinstructs insomniacs to leave bed unless sleepy.

doi:10.1016/j.clinph.2007.05.059

e202 Japanese Society of Clinical Neurophysiology / Clinical Neurophysiology 118 (2007) e189–e202