Abstract
Research with infants has illustrated the development of adult-like smooth pursuit gain by five months-of-age and links this to the development of sensitivity to depth from motion parallax. Ocular following response eye movements to radial optic flow stimuli may also be an indicator of sensitivity to changes in depth. An expanding flow field elicits convergent eye movements while a contracting one elicits divergent eye movements. This response suggests the visual system is interpreting the radial flow as a change in depth. We measured the oculomotor response to radial optic flow in infants across the age range where smooth pursuit gain is developing. Vergence eye movements were elicited from 56 infants 8-20 weeks-of-age. The stimulus comprised a radial optic flow pattern that expanded or contracted across eight 400 msec trials. The order of the four expanding and four contracting trials was randomized and eye position was monitored with a Tobii X120 eye-tracker. We defined the threshold for a vergence eye movement as velocity greater than 0.3 deg/sec. The majority of infants produced vergence eye movements in response to the expanding and contracting trials with about half producing either a convergence or divergence response appropriate to the stimuli. Approximately one-quarter produced both convergence and divergence responses. However, there was no relationship between age and the presence/absence of the vergence response or its velocity. We did find a significant positive correlation between age and smooth pursuit gain in a subset of these infants as expected. It may be that the vergence response is already developing at the youngest age. Similar to research on infants’ reactions to looming stimuli, these results suggest that sensitivity to depth from radial optic flow may develop very early.
Meeting abstract presented at VSS 2015