Cross-modal interactions and movement-related tactile gating: the role of vision

Abstract

When engaging with the environment, multisensory cues interact and are integrated to create a coherent representation of the world around us, process that has been suggested to be affected by the lack of visual feedback in blind individuals. In addition, the presence of voluntary movement seems to be responsible for suppressing somatosensory information that is processed by the cortex, which can lead to a worse encoding of tactile information. In this work, we aim to explore how multisensory processing can be affected by active movements and the role of vision in this process. To this end, we measure the precision of 18 sighted controls and 18 blind individuals in a velocity discrimination task. The participants were instructed to detect the stimulus that contained the faster speed, between a sequence of two, in both passive and active touch conditions. The sensory stimulation could be either just tactile or audio-tactile, where a non-informative sound occurred simultaneously with the tactile stimulation. The measure of precision was obtained by computing the Just Noticeable Difference (JND) of each participant. The results show worse precision in the bimodal audio-tactile sensory stimulation in the active condition for the sighted group but not for the blind one. In the sighted group, the noise of the tactile feedback might make them more vulnerable to the noisy interference of the audio modality; however, this is not the case for the blind one, which seems to be only affected by the movement itself. Our work should be considered when developing next-generation haptic devices; moreover, it supports the need for action in the blind population.