Effects of interstimulus interval on non-painful tactile brain responses and temporal processing of non-painful tactile stimuli: An electrophysiological approach

Objective: The current study aims to investigate the effects of different inter-stimulus intervals on habituation process and temporal time processing by using non-painful tactile stimuli. Method: Twenty-five right-handed healthy volunteers (11 male; mean age 21.7±3.28 years) participated to the study. The electroencephalography (EEG) were recorded from 64 channels during the recordings. Non-painful tactile stimuli (~140 kPa) were delivered to the right index finger via using a pneumatic stimulator. Somatosensory evoked potential (SEP) paradigm and Omitted stimulus paradigm were used in all session. Inter-stimulus interval (ISI) was selected as 2s, 4s, and 8s and applied in separate sessions. The peak-to-peak maximum amplidutes of N200 (N2) and P300 (P3) components were measured for three ISI. Primarly, nine electrodes (Fz, Fcz, Cz, Cpz, Pz, C3, C4, P3, P4) were analyzed. Results: According to the analysis, a significant ISI effect was found on both amplitudes and duration to non-painful tactile stimuli in all electrode areas. There was a significant increase in amplitudes of ppmaxN2P3 as ISI increased (p<0,001). Duration of N2P3 were also prolonged in line with ISI in all electrode areas (p=0,005). In the hemispheric approach, an increase in the amplitudes was observed as well as the duration of N2P3 prolonged with the increase of ISI in both hemisphere (p<0,001). Conclusion: The habituation process were associated with the increased amplitudes and prolonged brain responses to non-painful tactile stimuli under the increased ISI.