Motor strategies for spatial interaction in visually impaired children: towards the development of a multisensory device for sensorimotor rehabilitation

Goal-directed motor strategies, such as reaching and grasping, play a central role in early objects exploration, development of body–space representations, and gradual acquisition of functional adaptation to the surrounding environment. In congenital visual impairment, reduced or absent visual feedback from birth can affect perception–action calibration and reshape sensorimotor development. The main objective of my Ph.D. project was to investigate differences in goal-directed actions between visually impaired (VI) and sighted (S) children to inform the development of rehabilitation programs and multisensory devices to support visual disabilities. I hypothesized group differences in reach-to-grasp performance, affecting both temporal and motor parameters of action, with age related changes in execution patterns. Specifically, I expected S children to show faster pick up times than VI children. For lateral targets, I predicted reduced body midline crossing and no clear hand preference in VI children. I also expected movement times to decrease with age in both groups, alongside an age-related increase in midline crossing in VI group. Finally, I tested whether this variability in performance between groups could be predicted by resting state cortical dynamics. Analyses focused on occipital and central-parietal EEG activity, given the role of occipital-parietal networks in sensorimotor integration. I expected an association between resting state EEG activity and the temporal features of reach-to-grasp performance, particularly in VI children. To pursue this goal, using a multimodal approach, first I focused on reach-to-grasp abilities in VI and S preschooler children, measuring action timing (movement and pick up time) and motor strategies (body-midline crossing and hand preference when reaching for lateral targets). Second, I recorded high-density resting state EEG and quantified oscillatory (alpha and beta bands) and aperiodic (1/f slope and offset) spectral measures to test whether intrinsic cortical dynamics at rest predict developmental differences in reach-to-grasp performance as a function of visual experience. Results showed that VI children exhibited longer pick up times, reduced one-handed midline crossing for lateral targets with a developmental shift toward increased bimanual strategies, and no clear hand preference. Crucially, resting state EEG markers predicted pick up time differences in an age-dependent manner in VI children, indicating that the functional meaning of cortical dynamics at rest changes across early development when vision is absent. Together, this behavioral and neurophysiological evidence might identify early childhood as a sensitive window in which perception–action coupling is still being shaped and therefore more responsive to rehabilitation. Based on these findings, I contributed to the development and the validation of two multisensory devices (iHelpY and iReach) designed to support early body- and space-related exploration in VI infants and children. Specifically, I designed first iHelpY (a therapist-controlled proof-of-concept tested in a demonstrative comparison in a blind infant) and then iReach, including both absolute and relative spatial feedback into a two-unit multisensory device. Overall, this thesis defines developmentally sensitive behavioral and neural markers linked to a goal-driven action in VI children. These markers served as theorical frames for the development of a multisensory device to support tailored early rehabilitation.