Sleep disruption by nociceptive stimuli follows the apparition of a ‘cognitive’ wave, supposed to reflect the activation of a widespread cortical network (Bastuji et al 2008). The factors allowing the activation of this network are unknown and remain to be identified. The aim of the present study was to test if the characteristics of baseline cortical activity can predict reactivity to these nociceptive stimuli. For this purpose, intra-cerebral electrophysiological signal before nociceptive stimuli during sleep were analysed in the time-frequency domain.

Intracerebral recordings were obtained in 14 epileptic patients receiving thermo-nociceptive stimulations, calibrated slightly above the individual pain threshold, during whole night sleep. Spectral content of 5 seconds pre-stimulus EEG signal and phase coherence between posterior insula and 14 other brain areas were compared according to presence or absence of arousal post-stimulus, during sleep N2 and paradoxical sleep (PS). 

Spectral power of delta activity pre-stimulus was significantly lower before arousal reaction as compared to that with no arousal in N2 (p<0.0001), and higher in PS (p<0.001). Pre-stimulus phase coherence between posterior insula and other brain areas was significantly higher before post-stimulus arousal as compared to no arousal, and this in N2 as well as in PS.

Arousal occurrence is related to a lighter sleep when the nociceptive stimulus is delivered and a higher functional connectivity between the sensory and other cortices. This greater connectivity between sensory and association areas may facilitate information propagation leading to conscious perception and physiological response.

BASELINE CORTICAL ACTIVITY PREDICTS REACTIVITY TO NOCICEPTIVE STIMULI DURING SLEEP