Abstract
The extrastriate body area (EBA) is a body-selective region within the occipitotemporal cortex. EBA has a key role in processing visual information of others' whole bodies and body-parts, however it is unclear to what extent the categorical representation in EBA is influenced by individuals' experience across the lifespan. Here, individuals with acquired or congenital upper limb loss (hereafter one-handers) were tested to investigate how limb loss and body-part substitution (wearing a prosthesis) shape reorganisation in EBA. EBA was independently localised in 32 one-handers and 24 two-handed controls by contrasting images of headless-bodies and objects. Participants viewed images of upper-limbs (lateralised to match the missing side of one-handers), others' prostheses, and one-handers' own prosthesis in an event-related design. Tools, known to activate an area overlapping with EBA, were also presented. Reorganization of EBA was assessed by comparing the distances between these objects using representational similarity analysis. Limb loss did not significantly affect visual representation of the missing upper-limb in EBA, as no differences were found between one-handers' and controls non-dominant limb representation. However, experience-dependent reorganisation was found in one-handers' prosthesis representation. One-handers who use a prosthesis more in daily life, show greater representation of others' prostheses as an independent category, distinct from hands and tools. When observing their own prosthesis, congenital one-handers' visual representation was more similar to upper limbs than tools. This shift of one's own prosthesis representation towards the upper-limb representation was not evident in acquired amputees. This result is consistent with recent evidence suggesting a less rigid categorisation of upper limbs in individuals who lost their hand earlier in life. Together our results suggest that the EBA categorical representation is affected by one's experience with body-part 'substitution'. EBA representation structure might be both adaptable, in creating new categorical representations, and rigid in inflexible category boundaries after development.
Meeting abstract presented at VSS 2018