Klára Horváth*1, Péter Simor*2, Piroska Sándor1, Réka Vida1, Réka Lihi3, Zita Sulyok4, Róbert Bódizs1


*These authors contributed equally to this work and should be considered co-first authors

1 Institute of Behavioural Sciences, Semmelweis University, Budapest

2 Department of Cognitive Sciences, Budapest University of Technology and Economics

3 Eötvös Loránd University, Budapest

4 University of Szeged

Correspondence: horv.klara@gmail.com



Nightmare disorder characterised by recurrent vivid, dysphoric dreams charged with negative emotions is one of the most often sleep problems. While there are two studies about the sleep architecture of nightmare sufferers (NS), as far as we know, the sleep EEG characteristics of them have not been investigated yet.

Psychological (Beck Depression and State-Trait Anxiety Inventory) and two-night polysomnographic testing were conducted on 21 university students (10 NS, 11 control) without any prior history of mental or chronic somatic disease. EEG spectra were obtained by using Fast-Fourier Transformation on the second night recordings for REM and NREM separately. We examined the group differences by ANCOVA controlling for the BDI and STAI score.

In the nightmare group higher NREM theta (4,25-7,5 Hz) and high sigma (12,75-15 Hz) activities were found mainly at the centro-parietal region and the frontal area, respectively. The frontal high sigma activity was correlated significantly with poor sleep assessed by the Groningen Sleep Quality Scale. No significant differences in REM spectra have been observed.

The results suggest that NS differ from controls more in NREM than in REM sleep. The covert REM sleep phenomena might explain the higher theta activity in NS.


Keywords: nightmare, sleep, EEG, dreaming, covert REM sleep, sigma activity, sleep quality