Sensory brain responses and lateralization in nonpainful tactile stimuli during sleep

Aims and Objectives: The aim of this study was to investigate the difference between sensory brain responses of nonpainful tactile stimuli applied to the fingers of the right-hand dominant individuals between the hemispheres. Materials and Methods: Nineteen healthy volunteers (9 women, mean age ± standard deviation: 23.00 ± 2.24 years) participated in the study. Electroencephalogram (EEG) recordings were taken from 40 channels polysomnography system. A uniform nonpainful stimulus was applied to two fingers (index and middle fingers) of the right and left hand with a pneumatic stimulator unit. Results: Non-rapid eye movement sleep (NREM) whole night sleep-related potentials were evaluated. When the stimulus was applied to the right hand, central and parietal regions of the P50 response component appeared significantly earlier in the left hemisphere. When the left-hand stimulus was applied, the P50 and N100 response components appeared significantly early in central, parietal, and temporal regions in the left hemisphere. Hence, amplitudes of the right-hand response components (P50 and N100) were found to be greater in the central, parietal, and temporal regions in the left hemisphere. When the stimulus is applied to the left hand, the amplitude of the P50 component was greater in the central and temporal regions in the left hemisphere. Conclusion: P50 and N100 are components related to sensory processing. The difference in latency and amplitude observed in these components between hemispheres indicates the presence of lateralization in sensory processing during sleep.