Mia W. Nevin¹, Isabel B. Moody¹, Claudia C. Gonzalez¹, Uma Shahani², Isobel Hay³, Laura M. Ward⁴, Jenni M. Karl¹; ¹Thompson Rivers University, ²Glasgow Caledonian University, ³NHS Dumfries and Galloway, ⁴University of Dundee

Cerebral Visual Impairment (CVI) is the leading cause of visual impairment in children in developed countries. Ventral stream CVI, which affects perception, is more readily recognized than dorsal stream CVI, which affects visually-guided action, and is frequently mislabelled as Attention Deficit Hyperactivity Disorder (ADHD) or Autism Spectrum Disorder (ASD). A comprehensive description of reach-to-grasp behaviour in dorsal CVI is not currently available but could aid its diagnosis. We hypothesized that children with dorsal CVI would alter their movements to compensate for a dorsal stream impairment when performing visually guided reach-to-grasp actions. Participants reached to grasp blocks of increasing size and complexity from a pedestal while their movements were video recorded from the lateral and frontal perspective. They completed the task with, then without, vision. The results revealed that sighted neurotypical children consistently employed a visually-guided strategy characterized by preshaping their hand to the size of the block, contacting it with their distal fingertips, and efficiently gripping it with minimal adjustments. In contrast, dorsal CVI participants approached the block with inconsistent trajectories and less accurate preshaping. The way they contacted the blocks was more varied than controls. They made contact with a variety of digit and/or hand configurations; this seemed to influence the atypicality of the grasp types they used, as well as the number of post-contact adjustments they were required to make to achieve a more optimal grip. When vision was occluded, the two groups did not differ from one another – they consistently transported an open hand towards the block, contacted it with the proximal fingers, and used post-contact adjustments to eventually achieve an efficient grip. The results suggest that children with dorsal CVI adopt unique multisensory control strategies that incorporate haptic feedback to compensate for impaired visual guidance when performing visually guided, but not unsighted, reach-to-grasp actions.

Acknowledgements: We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), [funding reference number RGPIN-2017-05995] and Thompson Rivers University.