Pantomime-grasping: Tactile processing is altered from relative to absolute only when haptic calibration is allowed


Tactile- or mechanoreceptive-guided pantomime-grasping is described as a non-visual grasp performed to the location of a target previously presented on an individuals' limb (i.e., palm). Our group's previous work has shown that relative tactile information mediate this type of pantomime action and is a result our group has taken to evince a perception-based mode of control. Notably, however, receiving haptic feedback (i.e., proprioceptive-based feedback from thumb and forefinger position) about target size through physically grasping an object following a tactile-guided pantomime-grasp alters the mediation of motor output from relative to absolute size information. Thus, our group has proposed that the provision of haptic feedback engenders the computation of an error signal related to "expected" and "actual" haptic information and hence supports an absolute haptic calibration. The goal of the present study was to determine whether the aforementioned absolute calibration is specific to the provision of haptic feedback as opposed to being modality-independent. To that end, participants' performed tactile-guided pantomime-grasps in conditions wherein haptic or visual feedback about target size was provided at the end of the response. In particular, for the haptic feedback condition participants were able to grasp a veridical target, whereas in the visual feedback condition a virtual visual rendering of the veridical target was provided. Results showed that haptic – but not visual – feedback supports an absolute calibration process. Accordingly, we propose that terminal haptic feedback is a specific sensory consequence necessary to support an absolute haptic calibration.

Acknowledgments: Natural Sciences and Engineering Research Council of Canada (NSERC)