The Role of Motor Learning in Spatial Adaptation near a Tool

Abstract

Some visual-tactile (bimodal) cells have visual receptive fields (vRFs) that overlap and extend moderately beyond the skin of the hand. Neurophysiological evidence suggests, however, that a vRF will grow to encompass a hand-held tool following active tool use but not after passive holding. Why does active tool use, and not passive holding, lead to spatial adaptation near a tool? We asked whether spatial adaptation could be the result of motor or visual experience with the tool, and we distinguished between these alternatives by isolating motor from visual experience with the tool. Participants learned to use a novel, weighted tool. The active training group received both motor and visual experience with the tool, the passive training group received visual experience with the tool, but no motor experience, and finally, a no-training control group received neither visual nor motor experience using the tool. After training, we used a cueing paradigm to measure how quickly participants detected targets, varying whether the tool was placed near or far from the target display. Only the active training group detected targets more quickly when the tool was placed near, rather than far, from the target display. This effect of tool location was not present for either the passive-training or control groups. These results suggest that motor learning influences how visual space around the tool is represented.

Visual illusion of tool use recalibrates tactile perception

“…were necessary for embodiment (Brown et al, 2011; Cardinali, Brozzoli, Luauté, et al, 2016; Rademaker et al, 2014), there should be no modulation of tactile perception on a stationary arm. In contrast to this prediction, visual feedback produced clear tool embodiment on the stationary left forearm.…”

“…Using a tool (as opposed to passive handling) has been found to be necessary for tool embodiment (Brown et al, 2011; Farnè et al, 2005; Garbarini et al, 2015; Maravita et al, 2002; Witt et al, 2005), underscoring the importance of use-related sensory and motor signals. In Experiment 4, we tested whether this was also the case for illusory tool use.…”

“…Indeed, studies have reported that active use of the tool, as opposed to mere passive holding, is necessary for embodiment (Garbarini et al, 2015; Maravita et al, 2002; Witt, Proffitt, & Epstein, 2005; though, see Baccarini et al, 2014). This suggests that a range of specific motor and kinesthetic factors (Wolpert & Ghahramani, 2000)—such as efference copies and somatosensory feedback—may be critical for the process (Brown, Doole, & Malfait, 2011; Rademaker, Wu, Bloem, & Sack, 2014). Indeed, a recent study failed to find evidence for tool-modulated reaching kinematics in a deafferented patient (Cardinali, Brozzoli, Luauté, Roy, & Farnè, 2016).…”

Grab an object with a tool and change your body: tool-use-dependent changes of body representation for action

“…However, a large amount of the literature supports the notion that the brain is capable to adapt when changes in the environment happen. For example, when an external force is applied to the arm of a subject asked to point to a target (Bhushan and Shadmehr 1999;Diedrichsen et al 2005;Ostry et al 2010) or when inertial properties of a tool are invisibly altered (Brown et al, 2011), the subject will show, at the beginning, a deviation from the desired and requested trajectory resulting in a discrepancy between the planned movement and the desired consequences. This discrepancy arises from the fact that the movement has been planned based on previous knowledge about the environment and/or the hand-held object (thus ignoring the unexpected perturbation).…”

“…This discrepancy arises from the fact that the movement has been planned based on previous knowledge about the environment and/or the hand-held object (thus ignoring the unexpected perturbation). By practicing the movement under the same (new) condition over and over, the subject will learn to compensate for the introduced force and eventually reach the desired level of performance (Bhushan and Shadmehr 1999;Diedrichsen et al 2005;Massen and Prinz 2009;Brown et al 2011). Recently, Ostry et al (2010) used a force Weld paradigm to study the potential consequences of motor learning on the perceptual domain.…”