Vision facilitates tactile perception when grasping an object

Georgiana Juravle,Alessandro Farnè,Francisco L Colino,Xhino Meleqi,Gordon Binsted

doi:10.1038/s41598-018-33916-8

Abstract

Tactile sensitivity measured on the hand is significantly decreased for a moving (MH), as opposed to a resting hand (RH). This process (i.e., tactile suppression) is affected by the availability of visual information during goal-directed action. However, the timing of the contribution of visual information is currently unclear for reach-to-grasp movements, especially in the period before the digits land on the object to grasp it. Here participants reached for, grasped, and lifted an object placed in front of them in conditions of full/limited vision. Tactile perception was assessed by measures of signal detection theory (d’ & c’). Electro-cutaneous stimulation could be delivered/not at the MH/RH, either during movement preparation, execution, before grasping, or while lifting the object. Results confirm tactile gating at the MH. This result is accompanied by a significant conservative criterion shift at the MH for the latter movement stages. Importantly, visual information enhances MH sensitivity just before grasping the object, but also improves RH sensitivity, during object lift. These findings reveal that tactile suppression is shaped by visual inputs at critical action stages. Further, they indicate that such a time-dependent modulation from vision to touch extends beyond the MH, suggesting a dynamic monitoring of the grasp space.

Highlights

Tactile suppression is a well-known phenomenon characterized by a decrement in tactile sensitivity, typically occurring on our upper limbs in relation to movements that we perform
The analysis indicated a significant main effect of HAND [F(1,14) = 7.17, p = 0.018, η2p = 0.339], with participants more likely to say no tactile stimulus was present when stimulation was delivered at their moving hand [M = 0.30, SE = 0.05], as compared to when stimulation was delivered to their resting hand [M = 0.15, SE = 0.02]
We focused on the stimulation delivery timings of before grasping an object, as well as when lifting said object, with the purpose of elucidating the specific timing of the previously reported tactile suppression reduction when vision is available[6]

Summary

Introduction

Tactile suppression is a well-known phenomenon characterized by a decrement in tactile sensitivity, typically occurring on our upper limbs in relation to movements that we perform. Our starting point is the crucial finding that tactile suppression manifests differently at each digit involved in the process of reaching and grasping an object Colino and his colleagues were the first to demonstrate that the index finger involved in a grasping action experiences less suppression, as compared to the little finger not participating in the grasp, or the completely unrelated forearm of the resting hand[7,11]. Having convincingly established the relevance of the motor effector when assessing tactile suppression, the authors investigated whether the tactile suppression effect is affected by the availability of visual information during movement They had their participants perform reach-to-grasp movements under conditions of full vision, or limited visual availability, with only a short period of fixation at the beginning of the movement, and the rest of the movement performed with vision occluded. Their results indicated that visual information availability contributes to decrease the overall magnitude of tactile suppression experienced during movement[6]

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Conclusion