Perception of body shape and size without touch or proprioception: evidence from individuals with congenital and acquired neuropathy

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Authors

Abstract

The degree to which mental representations of the body can be established and maintained without somatosensory input remains unclear. We contrast two "deafferented" adults, one who acquired large fibre sensory loss as an adult (IW) and another who was born without somatosensation (KS). We compared their responses to those of matched controls in three perceptual tasks: first accuracy of their mental image of their hands (assessed by testing recognition of correct hand length/width ratio in distorted photographs and by locating landmarks on the unseen hand); then accuracy of arm length judgements (assessed by judgement of reaching distance), and finally, we tested for an attentional bias towards peri-personal space (assessed by reaction times to visual target presentation). We hypothesised that IW would demonstrate responses consistent with him accessing conscious knowledge, whereas KS might show evidence of responses dependent on non-conscious mechanisms. In the first two experiments, both participants were able to give consistent responses about hand shape and arm length, but IW displayed a better awareness of hand shape than KS (and controls). KS demonstrated poorer spatial accuracy in reporting hand landmarks than both IW and controls, and appears to have less awareness of her hands. Reach distance was overestimated by both IW and KS, as it was for controls; the precision of their judgements was slightly lower than that of the controls. In the attentional task, IW showed no reaction time differences across conditions in the visual detection task, unlike controls, suggesting that he has no peri-personal bias of attention. In contrast, KS did show target location-dependent modulation of reaction times, when her hands were visible. We suggest that both IW and KS can access a conscious body image, although its accuracy may reflect their different experience of hand action. Acquired sensory loss has deprived IW of any subconscious body awareness, but the congenital absence of somatosensation may have led to its partial replacement by a form of visual proprioception in KS.

Bibliographic note

Funding Information: We thank IW and KS for their dedicated participation. We also thank Fabrice Sarlegna for his valuable comments. This work was support by NIH-NINDS grant R03NS113752. Publisher Copyright: © 2021, The Author(s).

Details

Original languageEnglish
Pages (from-to)1203-1221
Number of pages19
JournalExperimental Brain Research
Volume239
Issue number4
Early online date12 Feb 2021
Publication statusPublished - Apr 2021

Keywords

  • Body representation, Deafferentation, Sensory neuropathy, Somatosensation

ASJC Scopus subject areas