Tactile Gap Detection Deteriorates during Bimanual Symmetrical Movements under Mirror Visual Feedback.

Janet H Bultitude,Charles Spence,Georgiana Juravle,Mikhail A Lebedev

doi:10.1371/journal.pone.0146077

Abstract

It has been suggested that incongruence between signals for motor intention and sensory input can cause pain and other sensory abnormalities. This claim is supported by reports that moving in an environment of induced sensorimotor conflict leads to elevated pain and sensory symptoms in those with certain painful conditions. Similar procedures can lead to reports of anomalous sensations in healthy volunteers too. In the present study, we used mirror visual feedback to investigate the effects of sensorimotor incongruence on responses to stimuli that arise from sources external to the body, in particular, touch. Incongruence between the sensory and motor signals for the right arm was manipulated by having the participants make symmetrical or asymmetrical movements while watching a reflection of their left arm in a parasagittal mirror, or the left hand surface of a similarly positioned opaque board. In contrast to our prediction, sensitivity to the presence of gaps in tactile stimulation of the right forearm was not reduced when participants made asymmetrical movements during mirror visual feedback, as compared to when they made symmetrical or asymmetrical movements with no visual feedback. Instead, sensitivity was reduced when participants made symmetrical movements during mirror visual feedback relative to the other three conditions. We suggest that small discrepancies between sensory and motor information, as they occur during mirror visual feedback with symmetrical movements, can impair tactile processing. In contrast, asymmetrical movements with mirror visual feedback may not impact tactile processing because the larger discrepancies between sensory and motor information may prevent the integration of these sources of information. These results contrast with previous reports of anomalous sensations during exposure to both low and high sensorimotor conflict, but are nevertheless in agreement with a forward model interpretation of perceptual modulations during goal directed movement.

Highlights

For any self-generated movement, the central nervous system produces an internal copy of the motor command that is cross-referenced against sensory input
This “efference copy” signals motor intention and allows us to differentiate between self-generated movements and those that are caused by external forces acting on our body [1]
Harris [4] suggested that incongruence between cortical signalling of motor intention and sensory input may lead to experiences of pain

Summary

Introduction

For any self-generated movement, the central nervous system produces an internal copy of the motor command that is cross-referenced against sensory input. Harris [4] suggested that incongruence between cortical signalling of motor intention and sensory input may lead to experiences of pain This “sensorimotor” theory of pain may explain conditions in which pain and other symptoms arise in the absence of, or that are disproportionate to, any observable limb pathology, such as repetitive strain injury, musician’s dystonia, phantom limb pain, and Complex Regional Pain Syndrome (CRPS) [4,5]. Studies of those suffering from such conditions have revealed abnormal sensory processing [6,7,8,9] and changes in cortical representations of the affected limb [10,11,12]. These findings are consistent with Harris’ [4] suggestion that inaccurate sensory and motor signals stemming from altered receptive fields may aggravate the nociceptive system

Methods

Results

Conclusion