Abstract
When sliding our fingertip against a textured surface, complex vibrations are produced in the skin. It is increasingly recognised that the neural transduction and processing of these vibrations plays an important role in the dynamic tactile perception of textures. The aim of the present study was to develop a novel means to tag the cortical activity related to the processing of these vibrations, by periodically modulating the amplitude of texture exploration-induced vibrations such as to record a steady-state evoked potential (SS-EP). The EEG was recorded while the right index fingertip was scanned against four different textures using a constant exploration velocity. Amplitude modulation of the elicited vibrations was achieved by periodically modulating the force applied against the finger. Frequency analysis of the recorded EEG signals showed that modulation of the vibrations induced by the fingertip-texture interactions elicited an SS-EP at the frequency of modulation (3 Hz) as well as its second harmonic (6 Hz), maximal over parietal regions contralateral to the stimulated side. Textures generating stronger vibrations also generated SS-EPs of greater magnitude. Our results suggest that frequency tagging using SS-EPs can be used to isolate and explore the brain activity related to the tactile exploration of natural textures.
Highlights
When sliding our fingertip against a textured surface, complex vibrations are produced in the skin
At the level of peripheral mechanoreceptors, previous research focusing on very coarse textures, such as Braille dot patterns, suggested that the dynamic perception of textures is essentially reflected in the spatial pattern of activity elicited in slowly adapting Type I (SAI) mechanoreceptors, having very punctate receptive fields[8]
A significant increase of EEG signal amplitude was observed at the frequency of the second harmonic (6 Hz). This increase was significant when the fingertip was scanned against baking paper (t(11) = 3.91, p = 0.002, 95% CI [0.035, 0.127]), but not when it was scanned against denim (t(11) = 1.42, p = 0.182, 95% CI [− 0.013, 0.061]), (Fig. 2)
Summary
When sliding our fingertip against a textured surface, complex vibrations are produced in the skin. The identification and discrimination of coarse textures would predominantly rely on a spatial decoding of the activity generated within populations of slowly-adapting SAI mechanoreceptors, whereas the identification of fine textures would predominantly rely on a temporal decoding of the frequency content of the activity generated within rapidly-adapting RA and PC mechanoreceptors[11]. This temporal mechanism implies that texture-elicited vibrations play an important role in texture perception[12]. Supporting this notion, it has been shown that ring www.nature.com/scientificreports/
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