Current Topics

The heterogeneity of REM sleep

Rapid Eye Movement sleep is a unique sleep state characterized by intense sensorimotor and oneiric (dream) activity accompanied by inhibited motor output and reduced environmental processing. Nevertheless, REM sleep is composed of two, markedly different brain states, a phasic and a tonic microstate that alternate during REM sleep cycles. These microstates differ regarding arousal thresholds, sensory processing and presumably mental activity. Our aim is to examine the dynamic aspects of sleep-specific neural activity within the phasic and tonic REM state in order to understand their functions, as well as their relevance to information-processing and influence on dream experiences.

Simor, P., Gombos, F., Szakadát, S., Sándor, P. and Bódizs, R. (2016). EEG spectral power in phasic and tonic REM sleep: different patterns in young adults and children. Journal of Sleep Research. 25, 3, 269-277. doi: 10.1111/jsr.12376

Simor, P., Gombos, F., Blaskovich, B., Bódizs, R. Long-range alpha/beta and short-range gamma EEG synchronization distinguishes phasic and tonic REM periods. SLEEP,  zsx210,


Nightmares are intense and highly unpleasant mental experiences that occur usually – but not exclusively – during late-night Rapid Eye Movement (REM) sleep and often provoke abrupt awakenings. The clinical relevance of nightmares should not be underestimated given their high incidence in psychiatric populations, co-morbidity with insomniac symptoms and their association with waking affective as well as cognitive dysfunctions. In this line of research we investigate the personality correlates, neurocognitive and neurophysiological aspects of nightmare disorder. Our aim is to develop an integrative model of nightmare disorder that might facilitate the scientific understanding of this specific sleep disorder and foster therapeutic interventions and treatment procedures.

Simor, P., Körmendi, J., Horváth, K., Gombos, F., Ujma, P., Bódizs, R. (2014) Electroencephalographic and Autonomic Alterations in Nightmare Disorder during Pre-and Post-REM periods. Brain and Cognition, 91, 62-70. DOI: 10.1016/j.bandc.2014.08.004

Simor, P., Horváth, K., Ujma, P., Gombos, F., Bódizs, R. (2013). Fluctuations between sleep and wakefulness: wake-like features indicated by increased EEG alpha power during different sleep stages in nightmare disorder. Biological Psychology, 94, 592-600.

Simor, P., Bódizs, R., Horváth, K., Ferri, R. (2013). Disturbed dreaming and the instability of sleep: altered NREM sleep microstructure in subjects with frequent nightmares as revealed by the cyclic alternating pattern. SLEEP, 36(3), 413-419.

Chronotype, personality and cognition

This line of research examines diurnal preferences (morningness-eveningness) in relation to psychological adjustment and sleep quality in healthy and psychiatric populations. In addition, we are interested in the effects of synchrony; therefore, we examine how the time of testing modulates the associations between chronotype and cognitive performance.

Simor, P. and Polner, B. (2017). Differential influence of asynchrony in early and late chronotypes on convergent thinking. Chronobiology International, 34, 1, 118–128.

Simor, P., Zavecz, Zs., Pálosi, V., Török, Cs, Köteles, F. (2015) The influence of sleep complaints on the association between chronotype and negative emotionality in young adults. Chronobiology International, 32(1), 1-10. DOI:10.3109/07420528.2014.935786

Sleep and memory consolidation

Off-line memory consolidation is influenced by emotional, reward-related and cognitive processes during encoding. Research indicates that sleep selectively facilitates the consolidation of memories that are relevant for the future. In our laboratory, we are investigating the role of sleep (daytime naps and nocturnal sleep) in off-line memory consolidation. In our experiments, we are manipulating the perceived relevance of newly acquired memory elements to examine the effects of sleep on memory performance. By these experiments, we would like to examine the consolidation processes of relevant and irrelevant memories. Furthermore, we are interested in the association between the consolidation of relevant material, sleep macrostructure and sleep-specific oscillations.

Blaskovich, B., Szőllősi, Á., Gombos, F., Racsmány, M., Simor, P. (2017). The benefit of directed forgetting persists after a daytime nap: the role of spindles and REM sleep in the consolidation of relevant memories. SLEEP, 40, 3. doi:10.1093/sleep/zsw076.