Time Course of Tactile Gating in a Reach-to-Grasp and Lift Task

Abstract

Humans' sensory systems are bombarded by myriad events every moment of our lives. Thus, it is crucial for sensory systems to choose and process critical sensory events deemed important for a given task and, indeed, those that affect survival. Tactile gating is well known, and defined as a reduced ability to detect and discriminate tactile events before and during movement. Also, different locations of the effector exhibit different magnitudes of sensitivity changes. The authors examined that time course of tactile gating in a reaching and grasping movement to characterize its behavior. Tactile stimulators were attached to the right and left mid-forearms and the right index finger and fifth digit. When participants performed reach-to-grasp and lift targets, tactile acuity decreased at the right forearm before movement onset (F. L. Colino, G. Buckingham, D. T. Cheng, P. van Donkelaar, & G. Binsted, 2014 ). However, tactile sensitivity at the right index finger decreased by nearly 20% contrary to expectations. This result reflecting that there may be an additional source acting to reduce inhibition related to tactile gating. Additionally, sensitivity improved as movement end approached. Collectively, the present results indicate that predictive and postdictive mechanisms strongly influence tactile gating.

Vision facilitates tactile perception when grasping an object

“…A similar pattern was reported for reaches 10 , as well as a significant deterioration in movement accuracy was reported following proprioceptive tendon vibration for the later stages of a goal-directed movement 19 . Even though performance deteriorates at the moving hand for both the preparatory and execution phases of the movement, the recorded average sensitivity is very good and comparable to the previous reports 5 , 7 , 11 . This may reflect an almost-ceiling effect given by the utilisation of the 90% detection threshold; future studies need to test a significantly lower threshold (e.g., uniform suppression was described throughout movement for discrimination thresholds tested at 79.4% correct responses 3 , 20 ).…”

“…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 . Further studies have attempted to replicate and extend claims on this finding; however, their methods violated the first rule of the timing of tactile suppression, by having delivered stimulation either too early (i.e., at movement initiation when suppression is maximal 12 ), or too late (i.e., once the movement has terminated 5 ).…”

“…To assess the temporal profile of vision’s contribution to tactile suppression, here we consider the tactile stimulation delivery timing, the effector relevance, and the requirements for tactile perception measurement during movement. For this, we define timing based on real-time spatial coordinates of the hand, as opposed to stimulation delivery relative to the imperative cue, as it was previously studied as far as relevance in tactile suppression is concerned 5 , 7 , 11 . Our participants reached for and grasped an object placed in front of them, under conditions of full visual information or limited visual information.…”

Prediction in goal-directed action

“…For example, an externally applied touch stimulus is perceived as weaker and as later in time when the limb is moving than when the limb is at rest. This has been shown for a wide variety of visuo-motor tasks, such as reaching (Fraser & Fiehler, 2018;Gertz, Voudouris, & Fiehler, 2017), grasping (Colino & Binsted, 2016;Colino, Buckingham, Cheng, van Donkelaar, & Binsted, 2014;Voudouris, Broda, & Fiehler, 2019), juggling (Juravle & Spence, 2011), and during gait (Duysens et al, 1995;Morita, Petersen, & Nielsen, 1998). Sensitivity to the external stimulus typically starts decreasing around 100 ms before movement onset and reaches its minimum during the movement (Buckingham, Carey, Colino, Degrosbois, & Binsted, 2010;Figure 6b).…”

“…This dilemma can be solved by dynamically adjusting the strength of sensory attenuation with respect to the relevance of the predicted sensory signals for a given task. For example, when performing a precision grasp, tactile sensitivity is less attenuated at the index finger, which is involved in the grasp, compared to the pinky or the forearm of the grasping limb (Colino et al, 2014;Colino & Binsted, 2016;Juravle, Colino, Meleqi, Binsted, & Farnè, 2018). This effect is temporally tuned to the time shortly before the start of the grasp, i.e., the time period critical for movement planning.…”