Cortical activations induced by electrical versus vibrotactile finger stimulation using EEG

Somatosensory evoked potentials (SEPs) recorded with electroencephalography offer insights into cortical responses to tactile stimulation, typically elicited through temporally precise electrical stimulation. Although vibrotactile stimulation is more ecologically valid but less common, studies directly comparing EEG responses to both electrical and vibrotactile finger stimulation are limited. This study examines and compares (a) cortical responses, (b) connectivity patterns, and (c) somatotopic accuracy of these stimulation types on the fingers. In two experiments, SEPs were recorded from healthy participants' right-hand finger stimulation, using either electrical (experiment 1, n=22) or vibrotactile (experiment 2, n=22) stimulation. Vibrotactile stimuli were delivered at 10, 50, and 250 Hz, targeting different ranges of tactile mechanoreceptors activations. Electrical stimulation reliability was assessed across two days, showing consistent SEP amplitudes and latencies. Both stimulation types generated three early components (P1, N1, P2), but all vibrotactile components were increasingly delayed compared to electrical stimulation. Vibrotactile stimulation exhibited stronger localized connectivity in early components (P1, N1) in the left hemisphere, while electrical stimulation showed broader connectivity at P2. Electrical stimulation provided a clearer somatotopic organization in the postcentral gyrus than vibrotactile stimulation. These findings suggest distinct processing for electrical versus vibrotactile finger stimulation. These two stimulation methods are not interchangeable in somatosensory studies: the temporal shift in vibrotactile responses reflects selective activation of Pacinian corpuscles, whereas electrical stimulation yields stronger generalized cortical processing. Electrical stimulation may engage a serial processing pathway starting in the primary somatosensory cortex, while vibrotactile stimulation could involve parallel processing in both primary and secondary somatosensory cortices.