Disappearing hemispheric lateralization in tactile habituation: an electrophysiological approach

Hemispheric asymmetry is well established in tactile processing, with higher cortical responses observed on the contralateral side of the stimulation area. However, the effect of the interstimulus interval on lateralization is poorly understood. In this context, we aimed to reveal the effects of repeated non-painful tactile stimuli on brain responses and hemispheric lateralization via static ISIs.

Twenty-six healthy participants (13 females; mean age 22.2 ± 3.30 years) participated in the study. Tactile stimuli were delivered to the index fingertip of the right hand via a pneumatic stimulator with static ISIs (2s, 4s, and 8s applied as separate sessions). Electroencephalography was performed throughout the procedure. We determined the ROI and primarily analysed nine electrodes (Fz, Cz, Pz, F3, C3, P3, F4, C4, and P4). We measured the peak-to-peak maximum amplitudes (PP_maxN2P3) between N₂₀₀ and P₃₀₀, labelling N₂₀₀ as N₂ and P₃₀₀ as P₃.

The results revealed no significant differences in the amplitudes of PP_maxN2P3 between the ipsilateral and contralateral hemispheres. Constant ISI manipulation altered the laterality of non-painful tactile stimuli. Furthermore, the amplitude of the brain responses would be higher in both the ipsilateral and contralateral hemispheres when the ISI increased. The evaluation of the duration of PP_maxN2P3 was prolonged in the frontal, central, and parietal areas.

The results indicate that manipulation of the interstimulus interval (ISI) can potentially negate the traditional contralateral advantage observed in tactile processing.