mise à jour du
13 octobre 2002
Sleep Research
EEG correlats of yawning during sleep onset
John V. Laing Robert D. Ogilvie
Psychology dep.; Brock University, St Cathatarines, Canada


Does yawning have an effect on arousal level ? Since we could not locate any studies in the literature addressing this question, the following analyses were planned as part of a series of investigations into sleep onset mechanisms. Twelve university students spent two consecutive nights each in the sleep lab where, in addition to standard polysomnographic recordings, respiration and behavioral responsiveness (Ogilvie & Wilkinson, 1984) assessed multiple transitions into sleep.
(Subjects were awakened after their first four sets of response failures, used in our lab to define sleep onset). These data were recorded on FM tape for subsequent computer analyses. Split screen CCTV monitoring of the subject and concurrent electrophysiological activity made it possible to identify instances of yawning and relate those episodes precisely to polygraphic and FM tape recordings.

There were 35 instances of yawning detected in 10 subjects over the 24 nights. However, the data were further seriously reduced by the requirement that there be 30 sec. of artifact-free EEG activity immediately preceding and following the yawn. As a control condition, EEG samples were taken from the same subjects before and after postural adjustments which produced movement artifacts of similar amplitudes and durations to those seen during yawning.

Thirty sec. samples of EEG (C3-A1) taken immediately prior to and following yawns and postural shifts were subjected to FFT analysis in 5 sec. blocks. Data from only four subjects were analyzed. Alpha, theta, and spindle frequencies were examined both in terms of absolute power and percent power (.4 to 25 Hz range) for three, 5 sec. blocks (5, 15, and 25 sec.).

These data were entered into 2 x 2 x 3 repeated measures ANOVAs (pre/post; yawn/postural shift; 3 time blocks).

There were no significant differences in absolute or percent power in any of the three frequency bands analyzed for any main effect or interaction. Unambiguous examples of yawning behavior recorded in the sleep lab prior to continuous nocturnal sleep do not appear to be associated with rapid changes in EEG-based levels of arousal.
mise à jour du
27 mars 2005
Sleep Research
Electrophysiological correlates of yawning
KL Regehr, RD Ogilvie, IA Simons
Psychology dep.; Brock University, St Cathatarines, Canada
Although an earlier study from this lab found no consistent relationship between yawning behavior and EEG changes, we decided to expand and replicate that work, for there were indications in Laing's data that differences might stabilize in a more comprehensive comparison of EEG activity 30 sec prior to and following a yawn. In that work, the clearest changes appeared 15 sec prior to and following the yawn in the Alpha and Theta frequencies.
Fifteen university students were paid to spend 2 nights in the sleep lab as part of a larger sleep onset investigation. After preparations for standard polysomnographic recording were complete, subjects were asked to read for 15 min immediately prior to a night's sleep. During that time, computerized EEG recordings were obtained, as was a simultaneous split screen videotaping of the subject reading and his/her concomitant EEG activity. The videotapes were viewed for clear instances of spontaneous yawning. Once yawning episodes were identified, the appropriate EEG epochs were located on the computer, and separate FFT analyses were obtained for each of 3 consecutive 10 sec blocks immediately prior to and following each yawn. Interest was focused on the middle period - 10 to 20 sec on either side of the yawn. 112 artifact free spontaneous yawns were analyzed. Yawn frequency varied from zero to 26 per subject (X= 13.17; SD= 5.74, N=12). Thus 12 separate FFTs were averaged within subjects, so that one set of RMS power measures per subject were treated statistically.
The primary analyses were 2 x 3 (pre/post yawn x 3, 10 sec blocks) MANOVAs calculated on RMS power measures for each of the 5 standard frequency bands. These analyses produced no significant main effects or interactions. However, since Laing had found significant changes when examining 5 sec blocks of EEG 15 to 20 sec prior to and following yawns, we had planned similar specific comparisons in this investigation. When correlated t-tests (df=11) were computed comparing the ore- and post-yawn 10 to 20 sec blocks (all 5 frequencies), the following significant differences were obtained: Delta (t = 2.23, p<.05; xpre = 502,xpost = 426); Theta (t = 4.15, p<.002; xpre = 172, xpost = 219); Sigma (t = 3.09, p<,01; xpre = 30.3, xpost = 37.8); Beta (t = 2.64, p<,02; xpre = 57.4, xpost = 72.3). These analyses indicate that there may be transient decreases in Delta and increases in Theta, Sigma (spindle), and Beta frequencies associated with yawning. The observed changes in Theta frequencies were consistent with those found by Laing, but no changes in Alpha were detected.
In summary, there are no relatively long-lasting changes in EEG activity attributable to yawning when pre- and postyawn samples are subjected to FFT analysis. Transient changes in Delta, Theta, Sigma, and Beta activity were noted, but similar effects were not detectable as little as 10 sec nearer or farther from the yawn. Thus yawning may produce fleeting changes in EEG indices of arousal, but presleep yawns do not represent points when the rate or direction of movement along the arousal continuum changes dramatically.
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