Can the observation of reach and grasp movements influence tactile processing?


Action can alter our perception of sensory events, but less is known about if and how action observation can alter our perception. Indeed, our perception of external tactile stimuli is reduced during movement and can be modulated by the speed of the movement (Cybulska-Klosowicz et al., 2011) and the relevance of touch information to the task (Manzone et al., 2018). However, the relationship between such modulating factors and tactile processing during action observation is not known. Thus, the current study explored tactile perception at a task-relevant location during the observation of reaching and grasping movements performed at different speeds. Specifically, participants observed videos of an anonymous model performing movements at a slow (i.e., peak velocity [PV]: 155 mm/second), medium (i.e., PV: 547 mm/s), or fast speed (i.e., PV: 955 mm/s). To assess tactile processing, weak electrical stimuli of different amplitudes were presented to participants' right thumbs when the observed model was at their starting position and prior to any movement, or when the observed model's limb reached its PV. Perceptual thresholds were then calculated for the pre-movement stimulation time and for each observed movement speed. When observing slow movements, participants' perceptual thresholds were significantly lower than for the pre-movement stimulation time, which did not differ from the threshold when observing movements with medium or fast peak limb velocities. Thus, as compared to pre-movement states, tactile perception during action observation can depend on the observed movement speed. More importantly, our data provides evidence for tactile facilitation when observing slower reaching movements.

Acknowledgments: University of Toronto, Ontario Research Fund, Canadian Foundation for Innovation, National Sciences and Engineering Research Council