Abstract
Visual deprivation in childhood can lead to lifelong impairments in multisensory processing. Here, the Size-Weight Illusion (SWI) was used to test whether visuo-haptic integration recovers after early visual deprivation. Normally sighted individuals perceive larger objects to be lighter than smaller objects of the same weight. In Experiment 1, individuals treated for dense bilateral congenital cataracts (who had no patterned visual experience at birth), individuals treated for developmental cataracts (who had patterned visual experience at birth, but were visually impaired), congenitally blind individuals and normally sighted individuals had to rate the weight of manually explored cubes that differed in size (Small, Medium, Large) across two possible weights (350 g, 700 g). In Experiment 2, individuals treated for dense bilateral congenital cataracts were compared to sighted individuals in a similar task using a string set-up, which removed haptic size cues. In both experiments, indistinguishable SWI effects were observed across all groups. These results provide evidence that early aberrant vision does not interfere with the development of the SWI, and suggest a recovery of the integration of size and weight cues provided by the visual and haptic modality.
Highlights
Visual deprivation in childhood can lead to lifelong impairments in multisensory processing
The PMv did not show an independent adaptation to size and weight properties, but adapted to the combination of these properties, providing neural evidence for the integration of concurrent but separate sensory input. These results suggest that early visual deprivation might affect the Size-Weight Illusion (SWI), if the ability to integrate visual and haptic cues does not recover
When z-scored weight ratings were assessed in a size-by-weight-by-group analysis of variance (ANOVA with repeated measures), all groups performed the task in a principled manner, as indicated by a main effect of weight, wherein the 700 g weight was rated as heavier than the 350 g weight (F(1,23) = 639.15, p < 0.001, ηg2 = 0.85)
Summary
Visual deprivation in childhood can lead to lifelong impairments in multisensory processing. Putzar et al.[9] tested the automatic detection of illusory contours in congenital cataract reversal individuals who had undergone cataract surgery between 1 and 17 months of age They observed deficits in individuals who experienced more than 5–6 months of visual deprivation, and interpreted this result as evidence for impairments in the automatic binding of visual features—i.e. visual feature binding. Visual motion after-effects (perception of stationary stimuli as moving in the direction opposite to previously presented moving stimuli) were found after auditory motion adaptation in cataract-reversal individuals[20], i.e., a cross-modal after-effect which has not been found in normally sighted individuals These results converge to the conclusion that multisensory binding processes do not fully recover after sight restoration in individuals with a history of congenital cataracts. Recent studies with cataract reversal individuals have demonstrated recovery of multisensory redundancy e ffects[2,21] and partial recovery for auditory-visual simultaneity judgements[22], multisensory binding based on more complex features, such as speech[14], seems to depend on early visual input
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