Seeing touch enhances the perception and processing of digitized gentle stroking

Abstract

Observing touch activates brain regions similar to those activated by experiencing actual touch, suggesting that visual information can cross-modally influence tactile perception. In this electroencephalography (EEG) study, we investigated how viewing visual displays of an arm being touched may affect the perception and processing of digitally rendered touch patterns designed to resemble either stroking or tapping. Thirty-one participants experienced touch patterns delivered to their left forearm via a wearable sleeve while viewing either a photo of an arm or spatiotemporally aligned videos of an arm being touched in synchrony with either of the two touch patterns. Continuity and pleasantness ratings of touch stimuli were higher for stroking than for tapping. Correlations between continuity and pleasantness ratings were stronger when touch was accompanied by videos of touch than by the photo of an arm. Analysis of evoked brain responses revealed visual modulation of touch processing at centroparietal electrodes beginning at around 0.9 s, with the cross-modal effects diverging between stroking and tapping at about 1.6 s. Furthermore, the interaction effects of cross-modal influences between stroking and tapping at the neural level positively correlated with the visual modulation of pleasantness ratings in two right frontal clusters at around 1.4 s and 1.8 s. These results suggest that observing touch influences the perception and processing of touch through initial sensory integration at centroparietal sites, followed by later frontal valuation processes. This extends previous findings on affective touch by demonstrating that visual inputs can cross-modally shape the hedonic evaluation of digitally actuated touch.