Visual Enhancement of Touch and the Bodily Self

Abstract

In Press, Consciousness and CognitionWord Count: 4,388 Touch and the Body 2 Abstract We experience our own body through both touch and vision. We further see that others' bodies are similar to our own body, but we have no direct experience of touch on others' bodies.Therefore, relations between vision and touch are important for the sense of self and for mental representation of one's own body. For example, seeing the hand improves tactile acuity on the hand, compared to seeing a non-hand object. While several studies have demonstrated this visual enhancement of touch (VET) effect, its relation to the 'bodily self', or mental representation of one's own body remains unclear. We examined whether VET is an effect of seeing a hand, or of seeing my hand, using the rubber hand illusion. In this illusion, a prosthetic hand which is brushed synchronously -but not asynchronously -with one's own hand is felt to actually be one's hand. Thus, we manipulated whether or not participants felt like they were looking directly at their hand, while holding the actual stimulus they viewed constant. Tactile acuity was measured by having participants judge the orientation of square-wave gratings. Two characteristic effects of VET were observed: (1) cross-modal enhancement from seeing the hand was inversely related to overall tactile acuity, and (2) participants near sensory threshold showed significant improvement following synchronous stroking, compared to asynchronous stroking or no stroking at all. These results demonstrate a clear functional relation between the bodily self and basic tactile perception.

Determination of interventions for upper extremity tactile impairment in children with cerebral palsy: a systematic review

“…This is commonly referred to as the visual enhancement of touch effect and suggests an important functional relationship between tactile perception and the mental representation of one's own body. 52 No studies employing mirror therapy or visual enhancement of touch have been reported for children with CP. However, as mirror therapy and visually enhanced touch strategies could be employed in children without incurring a risk of adverse effects, and potentially high compliance depending on the task, this particular mode of intervention should be investigated further in children with CP.…”

The Effect of Visual Capture Towards Subjective Embodiment Within the Full Body Illusion

“…However, the role of synchronous visuotactile integration as a necessary component to trigger illusory embodiment remains debated 20,21 . Research has shown that illusory embodiment could still be induced based purely on visual information of a fake body (part) in the absence of visuotactile stimulation [21][22][23] , or based on merely expected but not experienced synchronous tactile stimulation 24 , and even following asynchronous visuo-tactile stimulation, provided that spatial congruence is adhered to between the real and fake body (part) 25 (see 20 for review). Such evidence highlights that synchronous visuotactile input can strengthen illusory embodiment, by contributing to the downregulation in the weighting of proprioceptive signals regarding one's own limb position in relation to vision 26 , but may not be a necessary component to trigger this process 21,22,27 .…”

Effects of posture on tactile localization by 4 years of age are modulated by sight of the hands: evidence for an early acquired external spatial frame of reference for touch

“…Studies of the rubber hand illusion have demonstrated that vision of a fake hand being stroked can capture tactile sensations to the visual location of the stroke (Botvinick & Cohen, 1998;Pavani, Spence & Driver, 2000). In addition, viewing a hand receiving a tactile stimulus modulates processing in the somatosensory cortex (Longo, Pernigo & Haggard, 2011;Taylor-Clark, Kennett & Haggard, 2002;Cardini, Longo & Haggard, 2011), improves tactile acuity (Longo, Cardozo & Haggard, 2008;Press, Taylor-Clark, Kennett & Haggard, 2004), and can even reduce the intensity of acute pain (Longo, Iannetti, Mancini, Driver & Haggard, 2012).…”