Changing hands: persistent alterations to body image following brief exposure to multisensory distortions

Abstract

The dynamic flexibility of body representation has been highlighted through numerous lines of research that range from clinical studies reporting disorders of body ownership, to experimentally induced somatic illusions that have provided evidence for the embodiment of manipulated representations and even fake limbs. While most studies have reported that enlargement of body parts alters somatic perception, and that these can be more readily embodied, shrunken body parts have not been found to consistently alter somatic experiences, perhaps due to reduced feelings of ownership over smaller body parts. Over two experiments, we aimed to investigate the mechanisms responsible for altered somatic representations following exposure to both enlarged and shrunken body parts. Participants were given the impression that their hand and index finger were either longer or shorter than veridical length and asked to judge veridical finger length using online and offline size estimation tasks, as well as to report the degree of ownership towards the distorted finger and hand representations. Ownership was claimed over all distorted representations of the hand and finger and no differences were seen across ownership ratings, while the online and offline measurements of perceived size demonstrated differing response patterns. These findings suggest that ownership towards manipulated body representations is more bidirectional than previously thought and also suggest differences in perceived body representation with respect to the method of measurement suggesting that online and offline tasks may tap into different aspects of body representation.

Somatosensory-guided tool use modifies arm representation for action

“…While tool use under visual guidance might lead to incorporation 53 , the present findings suggest that, although sufficient for implicit tool incorporation in the body representation for action, proprioception might not be sufficient to trigger tool incorporation at a more explicit level (see also 11,54 ). While this finding could provide preliminary evidence that more explicit and conscious body representations, such as the Body Image, may be more resistant to some forms of tool use effects, further investigations using a wider range of Body Image tasks (see 55,56 ) are needed to better delineate the conditions of permeability of the explicit body representation to tool incorporation.…”

An investigation of contextual factors in the application of multisensory illusions for analgesia in hand osteoarthritis

“…The finding of no analgesic effect in the contextual control condition in which ownership remained high lends further support for this theory. However, ownership over a virtual limb does not necessarily lead to a loss of ownership over the actual limb [40, 41]. Furthermore, our findings show that although pain predicts a reduction of ownership over the painful hand, it is not necessary for analgesic effects to occur when viewing the hand directly.…”

Differential effects of minified and magnified mirror visual feedback on the underlying misperception of hand size

“…Body shape and size perceptions are maintained by the integration of sensory signals including visual and proprioceptive inputs (Lackner, 1988 ; Taylor-Clarke et al, 2004 ); therefore, altering these inputs through illusory manipulations gives rise to changes in body size perception and highlights the dynamic flexibility of our body representation. In line with this, studies employing size-altering visuo-proprioceptive manipulations (Newport et al, 2015 ; Perera, Newport, & McKenzie, 2017 ) and mirror visual feedback (MVF) paradigms (Mancini, Longo, Kammers, & Haggard, 2011 ) have provided evidence for ownership over body parts of increased and decreased size, thus highlighting the bi-directional flexibility of our own body representation. In MVF paradigms, a vertical mirror is placed perpendicular to the body midline.…”