Inter-stimulus Interval Effect on Tactile Habituation: An Electrophysiological Approach

Abstract

Objective: The current study aims to investigate different inter-stimulus interval effect on habituation process by using non-painful tactile stimuli. Methods: Twelve right-handed healthy volunteers (6 female; mean age: 22.9 ± 1.93 years) participated to the study. The electroencephalography (EEG) was recorded from 64 channels. Non-painful tactile stimuli (~140 kPa) were delivered to the right index finger via using a pneumatic stimulator. Somatosensory evoked potentials (SEP) paradigm was used in all session. Inter-stimulus interval (ISI) was selected as 2s, 4s, and 8s and applied in separate sessions (as ISI2, ISI4 and ISI8). Results: Peak-to-peak maximum amplitudes of N2, P3 and N4 components were measured for three different ISI and for three different electrode sites (Fz, Cz, Pz). The 3x3 repeated measures ANOVA test was employed for statistical analysis. According to the analysis, a significant inter-stimulus interval (ISI) effect was found on both PPmaxN2P3 and PPmaxP3N4 (p=0.004 and p=0.001 respectively). The amplitudes of ISI8 session in all electrode sites higher than ISI2 session for both PPmaxN2P3 (p=0.024) and PPmaxP3N4 (p=0.012). Also, ISI4 session has higher amplitudes than ISI2 session (p=0.05) for the PPmaxP3N4. Conclusion: This study revealed that the late components of SEPs are affected by the ISI change. The amplitudes of SEP components are increased as ISI increased.