Sleep talking versus sleep moaning: electrophysiological patterns preceding linguistic vocalizations during sleep

Abstract

Sleep talking (ST) has been rarely studied as an isolated phenomenon. Late investigations over the psycholinguistic features of vocal production in ST pointed to coherence with wake language formal features. Therefore, we investigated the EEG correlates of Verbal ST as the overt manifestation of sleep-related language processing, with the hypothesis of shared electrophysiological correlates with wake language production.From a sample of 155 highly frequent STs, we recorded 13 participants (age range 19-30y, mean age 24.6 ± 3.3; 7F) via vPSG for at least 2-consecutive nights, and a total of 28 nights. We first investigated the sleep macrostructure of STs compared to 13 age and gender matched subjects. We then compared the EEG signal before 21 Verbal STs vs. 21 Non-verbal STs (moaning, laughing, crying, ...) in 6 STs reporting both vocalization types in Stage 2 NREM sleep.The 2x2 mixed ANOVA Group x Night interaction showed no statistically significant effect for macrostructural variables, but significant main effects for Group with lower REM (%), TST, TBT SEI and greater NREM (%) for STs compared to controls.EEG statistical comparisons (paired-samples Student's t-Test) showed a decrement in power spectra for Verbal STs vs. Non-verbal STs within the theta and alpha EEG bands, strongly lateralized to the left hemisphere and localized on centro-parietal-occipitals channels. A single left parietal channel (P7) held significance after Bonferroni correction.Our results suggest shared neural mechanisms between Verbal ST and language processing during wakefulness and a possible functional overlapping with linguistic planning in wakefulness.

The Influence of Sleep Talking on Nocturnal Sleep and Sleep-Dependent Cognitive Processes

“…Somniloquy (Sleep Talking -ST) is defined as the production of unaware linguistic vocalizations during sleep [ 1 ], to be differentiated from other utterances such as mumbling, laughing, groaning, and whistling [ 2 , 3 ]. Other utterances, defined as Non-Verbal episodes [ 2 , 4 ], and ST could often occur together, as shown in a non-comorbid ST sample [ 2 ].…”

“…However, ST episodes would appear to affect nighttime sleep. A recent laboratory study showed that sleep-talking subjects have lower sleep efficiency than healthy subjects [ 2 ].…”

“…Some authors identified a high degree of concordance between words pronounced in ST episodes and dream reports [ 6 ], suggesting that ST may reflect cognitive processes. Specific EEG patterns preceding the onset of ST episodes mirror the EEG topography of wake linguistic planning and production [ 2 ]. These results suggested an elaboration of language occurring during sleep [ 1 , 2 , 4 ].…”

“…Specific EEG patterns preceding the onset of ST episodes mirror the EEG topography of wake linguistic planning and production [ 2 ]. These results suggested an elaboration of language occurring during sleep [ 1 , 2 , 4 ].…”

Parasomnias and Disruptive Sleep-Related Disorders: Insights from Local Sleep Findings

“…At present, the knowledge about the neural correlates of NREM parasomnias is still inconclusive. However, the research interest in the local electrophysiological features of NREM parasomnias is growing [ 7 , 8 , 9 ], and we believe that a further effort in the investigation of regional EEG patterns before parasomnia episodes could provide new insights into the functional significance of NREM parasomnias.…”