Brain responsiveness to non-painful tactile stimuli prior and during sleep

The purpose of this study is analyzing the responses to non-painful tactile stimuli prior-to-sleep (PS) and during the sleep. A total of 21 healthy participants (10 male, mean age ± SD 22.82 ± 1.12 years) were recruited and tested in this study. EEG recordings were taken from 40 channels. Single type of non-painful tactile stimuli was applied to the two fingers of the right hand by means of pneumatic stimulator. Sleep stages were scored according to American Academy of Sleep Medicine sleep scoring systems. Somatosensory-evoked potentials (SEPs) were analyzed for PS and each of sleep stages. While P50, N100, P200, N300, P900 and N_late components were recorded both PS and during the sleep, P300 and N450 were observed only in PS. Likewise, P450 and N550 components were observed only during the sleep cycle (light, deep and REM). P50, N100 and P200 components related to sensorial processing had relatively higher amplitudes in PS than in the sleep cycle. On the other hand, N300, P450, P900 and N_late responses had the highest amplitudes during sleep. The changes in brain responses to non-painful tactile stimuli PS and during the sleep were presented in this study. To our knowledge, it is the first study to demonstrate the eight SEP components all at once. Early components have been related to sensory processing and thus hint at the limitation of the brain towards external world for sleep, whereas later components show the network activity for sustaining the sleep environment.