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Right head-turning preference is assumed to be a developmental default. This motor asymmetry seems to influence the development of other lateralised behaviours-such as handedness-as a consequence of orienting vision towards the right side of the body. To document the role of visual experience in promoting lateralised functions we assessed head-turning preference and handedness in a group of congenitally blind human adults. We found a left-side preference for head turning but a clear righthandedness in the same individuals. This asymmetric relationship suggests that absence of visual experience can alter head-turning preference and that handedness can emerge without visual orientation towards the right side. Our findings shed new light on the role of visual sensory experience in shaping functional asymmetries and suggest that single-gene models and environment alone cannot fully explain the emergence of functional asymmetries in humans. © 2013 Taylor & Francis.

Sense of body ownership and body representation are fundamental parts of human consciousness, but the contribution of the visual modality to their development remains unclear. We tested congenitally and late blind adults on a somatosensory version of the rubber hand illusion, and on the Aristotle illusion, in which sighted controls touching a single sphere with crossed fingers commonly report perceiving two. We found that congenitally and late blind individuals did not report subjectively experiencing the rubber hand illusion. However, in an objective measure, the congenitally blind did not show a recalibration of the position of their hand towards the rubber hand while late blind and sighted individuals did. By contrast, all groups experienced the Aristotle illusion. This pattern of results provides evidence for a dissociation of the concepts of body ownership and spatial recalibration and, furthermore, suggests different reference frames for hands (external space) and fingers (anatomical space).

Several studies conducted in mammals and humans have shown that multisensory processing may be impaired following congenital sensory loss and in particular if no experience is achieved within specific early developmental time windows known as sensitive periods. In this study we investigated whether basic multisensory abilities are impaired in hearing-restored individuals with deafness acquired at different stages of development. To this aim, we tested congenitally and late deaf cochlear implant (CI) recipients, age-matched with two groups of hearing controls, on an audio-tactile redundancy paradigm, in which reaction times to unimodal and crossmodal redundant signals were measured. Our results showed that both congenitally and late deaf CI recipients were able to integrate audio-tactile stimuli, suggesting that congenital and acquired deafness does not prevent the development and recovery of basic multisensory processing. However, we found that congenitally deaf CI recipients had a lower multisensory gain compared to their matched controls, which may be explained by their faster responses to tactile stimuli. We discuss this finding in the context of reorganisation of the sensory systems following sensory loss and the possibility that these changes cannot be "rewired" through auditory reafferentation. © 2014 Nava et al.