Abstract
Crossmodal incursion associated with partial vision loss may affect auditory-visual processing in those with low vision as compared with the normally sighted. In particular, crossmodal plasticity during and following vision loss modifies auditory-visual connections, potentially causing the integration of crossmodal information to differ across visual field locations. A visual flash detection task and a double flash task were performed with 24 stimuli locations, eight each equally spaced circumferentially at 5, 10, and 15 degrees from fixation. The visual flash detection task tested sensitivity to the visual flashes used in the double flash task (5 flash present trials, and 1 flash absent trial in each location). The double flash task had 10 trials in each visual flash detection location. The patient responses were segregated spatially based on the visual flash detection task, enabling the evaluation of regions with visual perception surrounded by vision loss. Patients 1 and 2 have monocular impairment due to impact trauma and optic nerve disease, respectively (eyes tested separately). Nine naive sighted participants were also tested as controls (with both eyes open). The eye with vision loss exhibited significantly stronger double flash perception relative to the eye with normal visual perception (Patient 1 only, and locations with 5/5 flash detections only). Also, the eyes with vision loss in both patients exhibited significantly stronger double flash perception than controls (only locations with 5/5 flash detections were included). The stronger double flash perception observed in the eye with low vision as compared with the control eye could be due to diminished visual responses, ocular dominance differences, or crossmodal interactions early in the visual pathway (prior to merging of the binocular inputs, for example in LGN). This pilot data is suggestive of the potential reweighting of audition and vision, and the spatial redistribution of crossmodality, as visual perception is lost.