Analysis of the first night effect on EEG Hemispheric Asymmetry during waking state in young healthy adult

Marc-André Gingras^1,2, Sylvie Chouinard^1,2, Christianne Bolduc^1,3, Roger Godbout^1,4
1Laboratoire du sommeil, Hôpital Rivière-des-Prairies, 7070 boul. Perras, Montréal, Québec, CANADA H1E 1A4
²Département de Psychologie, Université du Québec à Montréal
³Département de Psychologie, Université de Montréal
⁴Département de Psychiatrie, Université de Montréal

Abstract: Eight right-handed participants (4 men, 4 women, 26.9 ± 4.9 years) were recorded for two consecutive nights in a sleep laboratory. Waking EEG recordings were obtained in the evening and in the morning of both night using a 10-electrode montage. In each case, 60 seconds of artefact-free samples were submitted to spectral analysis, and absolute power amplitude was extracted (µV/Hz, 0.75Hz to 24.75Hz) on 24 frequency bands of 1 Hz. Participants showed typical first night effect (FNE) on sleep parameters. The ANOVA showed neither a moment nor a night effect on measures of EEG lateralization. Our previous results showed a FNE on REM sleep EEG lateralization. Therefore, the FNE has different influences on waking and REM sleep EEG lateralization, including topographical distribution of activity. 

Introduction

The detrimental effect in healthy participants of having to sleep for a first night in a laboratory is a well-known phenomenon. Very little attention, however, has been given to the consequence of FNE on quantified EEG measures. We have recently shown that the FNE gives way to a leftward asymmetry of the prefrontal EEG in REM sleep [1].  The aim of the present study was to verify whether the FNE had an impact on waking quantified EEG measures taken in the morning and in the evening.

Methods

Eight right-handed healthy participants (4 men, 4 women, 26.9 ± 4.9 years) were recorded for two consecutive nights in a sleep laboratory. All were free from sleep disorders and from a personal or a familial (first degree) history of psychiatric or neurologic disorders. Subjects were asked to keep a regular sleep-wake schedule for 14 days before coming to the laboratory. Napping was not allowed on days prior to recordings. Both nights were scored according to Rechtschaffen & Kales (1968). EEG recordings were obtained in the evening (between 22h00 and 23h00) and in the morning (between 07h00 and 08h00). Subjects were recorded for five minutes with eyes closed. Bilateral frontal (Fp1,Fp2,F7,F8), central (C3,C4), temporal (T3,T4) and occipital (O1,O2) monopolar EEGs refered to linked ears were recorded. In each case, 15 four‑seconds artefact free epochs equally distributed were selected and submitted to Fast Fourier transform with a resolution of 0.25 Hz and a cosine window smoothing. Absolute power amplitude was extracted (µV/Hz, 0.75Hz to 24.75Hz) and 24 frequency bands of 1 Hz were created. The lateralization coefficient was calculated with the following formula : ((Right - Left) / (Right + Left)) x 100. Data is expressed as means ± S.E.M. Sleep parameters were compared using T-tests. Statistical comparisons of EEG lateralization coefficients were made using a 2 (moments) x 2 (night) x 24 (frequency) ANOVA.

Results

Participants showed a typical FNE for young healthy participants on sleep parameters (see Table 1). On the other hand, the ANOVA did not reveal a moment (F=0.2; p<.69) nor a night (F=2.4; p<.14) main effect nor an interaction effect (F=0.1; p<.76) on lateralization coefficients. Table 2 illustrates this with descriptive data on the pair of (prefrontal) electrodes which has previously shown a FNE upon REM sleep EEG lateralization analysis [1].

Discussion

The FNE has been first described almost 40 years ago in terms of macroscopic sleep structure, and has been replicated repeatedly since [2]. EEG power amplitude, however,  remains constant over the nights 1 and 2 in terms of waking and REM sleep EEG activity [4,5]. On the other hand we have recently observed a leftward shift of EEG activity on night 1 compared to night 2. Together with the negative results on waking EEG asymmetry presented here, we conclude that there exist a dissociation between sensitivity of waking and REM sleep EEG towards the FNE and that topographical influences are involved.

Table 1
First night effect on sleep parameters

TABLE 2
Descriptive statistics for prefrontal EEG power amplitudes (µV), grouped by frequency bands

Delta (0.75-3.75 Hz) ; Theta (3.75-6.75 Hz) ;

Alpha (6.75-12.75 Hz) ; Beta (12.75-20.75 Hz)

REFERENCES

[1] Gingras MA, Chouinard S, Braun CMJ, Godbout R. “Analysis of the first night effect on REM sleep quantified EEG : Power amplitude and hemisphere asymetry”, J. Sleep Res., In press (Abstract).

[2] Agnew HW, Webb WB, Williams RL. “The first night effect: an EEG study of sleep”, Psychophysiology, 2: pp.263-266, 1966.

[3] Forest G, Godbout R. “The effect of one night of total sleep deprivation on EEG spectral analysis in young healthy subjects”, Sleep, 22, pp.145-6, 1999.

[4] Gingras MA, Poulin J, Godbout R. “An analysis of the first night effect on REM sleep quantified EEG”, Sleep, 23, pp. A239, 2000.

[5] Gingras MA, Chouinard S, Godbout R. “Analysis of the first night effect on evening and morning waking quantified EEG”, Sleep, 24 (suppl.), pp. A104 , 2001.

Supported by the Canadian Institutes for Health Research.