Sleep talking vs. sleep moaning: electrophysiological patterns preceding linguistic vocalizations during sleep.

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.