title: Electroencephalographic and autonomic alterations in subjects with frequent nightmares during pre-and post-REM periods.
abstract: Abnormal arousal processes, sympathetic influences, as well as wake-like alpha activity during sleep were reported as pathophysiological features of Nightmare Disorder. We hypothesized that in Nightmare Disorder, wake-like cortical activity and peripheral measures linked to arousals would be triggered by physiological processes related to the initiation of REM periods. Therefore, we examined electroencephalographic (EEG), motor and autonomous (cardiac) activity in a group of nightmare (NM) and healthy control (CTL) subjects during sleep-state-transitions while controlling for the confounding effects of trait anxiety. Based on the second-nights' polysomnographic recordings of 19 Nightmare Disordered (NM) and 21 control (CTL) subjects, we examined the absolute power spectra focusing on the alpha range, measures of heart rate variability (HRV) and motor (muscle tone) activity during pre-REM and post-REM periods, separately. According to our results, the NM group exhibited increased alpha power during pre-REM, but not in post-REM, or stable, non-transitory periods. While CTL subjects showed increased HRV during pre-REM periods in contrast to post-REM ones, NM subjects did not exhibit such sleep state-specific differences in HRV, but showed more stable values across the examined sleep stages and less overall variability reflecting generally attenuated parasympathetic activity during sleep-state-transitions and during stable, non-transitory NREM states. These differences were not mediated by waking levels of trait anxiety. Moreover, in both groups, significant differences emerged regarding cortical and motor (muscle tone) activity between pre-REM and post-REM conditions, reflecting the heterogeneity of NREM sleep. Our findings indicate that NM subjects' sleep is compromised during NREM-REM transitions, but relatively stabilized after REM periods. The coexistence of sleep-like and wake-like cortical activity in NM subjects seems to be triggered by REM/WAKE promoting neural activity. We propose that increased arousal-related phenomena in NREM-REM transitions might reflect altered emotional processing in NM subjects.
authors.affiliation: Department of Cognitive Sciences, Budapest University of Technology and Economics, H-1111, Egry József u. 1, T. épület/V, Budapest, Hungary; Nyírő Gyula Hospital, National Institute of Psychiatry and Addictions, Budapest, Hungary. Electronic address: psimor@cogsci.bme.hu.
authors.forename: Péter
authors.initials: P
authors.lastname: Simor
authors.affiliation: Institute of Behavioural Sciences, Semmelweis University, H-1089, Nagyvárad tér 4, Budapest, Hungary.
authors.forename: János
authors.initials: J
authors.lastname: Körmendi
authors.affiliation: Department of Experimental Psychology, University of Oxford, South Parks Road, OX1 3UD Oxford, UK.
authors.forename: Klára
authors.initials: K
authors.lastname: Horváth
authors.affiliation: Department of General Psychology, Pázmány Péter Catholic University, 2087, Egyetem u. 1, Piliscsaba, Hungary.
authors.forename: Ferenc
authors.initials: F
authors.lastname: Gombos
authors.affiliation: Institute of Behavioural Sciences, Semmelweis University, H-1089, Nagyvárad tér 4, Budapest, Hungary.
authors.forename: Péter P
authors.initials: PP
authors.lastname: Ujma
authors.affiliation: Institute of Behavioural Sciences, Semmelweis University, H-1089, Nagyvárad tér 4, Budapest, Hungary; Department of General Psychology, Pázmány Péter Catholic University, 2087, Egyetem u. 1, Piliscsaba, Hungary.
authors.forename: Róbert
authors.initials: R
authors.lastname: Bódizs
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology*; D001341:Autonomic Nervous System / Q000502:physiology*; D004325:Dreams; D004569:Electroencephalography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D012894:Sleep Stages / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult
keywords: Alpha power; Dreaming; EEG; Heart rate variability; Nightmare; Sleep