JCJC - Jeunes chercheuses & jeunes chercheurs

Psychophysiological Investigation of human Cognition during Sleep – PICS

Submission summary

Researches of the second half of the XXth century have significantly improved our knowledge of the mechanisms generating and maintaining sleep. By contrast, sleep functions remain incompletely known. A large number of hypotheses converged to a physiological restoration function, for example energy conservation, brain thermoregulation, or tissue restoration. Surprisingly, the putative role of sleep in cognition was less investigated however many results in animals and humans demonstrated that some elaborated neurophysiological and cognitive processing are still active during sleep (brain plasticity, semantic discrimination, dream production, external stimuli incorporation into dream content). First, Several neurophysiological studies demonstrated a critical influence of sleep periods on memory consolidation be it motor or conceptual, implicit or explicit. Second, electrophysiological studies demonstrated a preserved ability of the sleeping brain to discriminate between different sounds and even between different words. Third, while we are sleeping, the brain produces the complex multisensory and bizarre stories that we experience during dreaming, in which external sensory perceptions happens to be incorporated. Finally, it turns out that the sleeping brain is less and less considered as a passive and isolated resting organ but more and more as an active processor (generating dreams) with modified functional organisation (e.g., with visual information processing flow going from associative to primary visual area) still interacting with the external world (e.g., processing auditory stimulations up to their semantic dimension). However a comprehensive theory about sleep and its putative function(s) is still lacking. The aim of this project is to progress in our understanding of sleep, exploring 1) the putative role of sleep in waking cognition (investigation of cognitive factors likely to influence dream content) and the remaining cognitive abilities of the sleeping brain (investigating the cerebral mechanism and cognitive counterparts of sensory integration). Behavioural (dream reports collection) and electrophysiologcal (scalp and intracranial EEG) studies are proposed to investigate 1) cerebral mechanism and cognitive counterparts (stimulus incorporation into dream content) of meaning words perception during sleep, 2) whether cognitive factors like learning or self-related affective concerns influence dream content. Data analysis will involve event related potential, time/frequency analysis of oscillations, and lexico-statistical analysis of dream reports. Results of this project promise to progress in our understanding of sleep cognitive function(s), A better understanding of sensory integration during sleep (i.e a physiological state of altered consciousness) seems a prerequisite for an adequate interpretation of brain response to sensory stimulation under pathological altered state of consciousness (coma, vegetative state, minimally conscious state). The use of early ERPs to sensory stimuli (like the mismatch negativity) already proved to be very useful in the outcome prediction of comatose patients (Fischer et al. 1999; Fischer et al. 2004). Perrin et al., (2006) showed that later waves like P300 could also be detected in some of these patients. A better understanding of late electrophysiological response during sleep may thus provide further tool for unconscious brain investigation. The study of subliminal perception at wake will importantly help this objective revealing the cerebral bases of conscious and unconscious perception. They promise to better understand whether unconscious perception differs or not in different physiological condition (sleep and wakefulness). A meta-analysis of these data with those previously obtained in comatose patients (Perrin et al., 2006) will further help to compare unconscious perception in different physiological and physiopathological conditions. Both scalp responses and time-frequency analyses will be investigated with the aim of testing whether different (and which) structures participate to conscious and unconscious perception, and whether synchronisation is dependent on the conscious/coherent representation of the stimulus. These analyses could be very helpful to find a physiological marker of stimulus consciousness, and thus very helpful to detect those patients who are aware of the stimulus but unable to communicate.

Project coordination

Perrine RUBY (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 187,000 euros
Beginning and duration of the scientific project: - 48 Months

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