Abstract
People who have lost one eye early in life have enhanced sound localization (Hoover et al., 2011), lack visual dominance (Moro & Steeves, 2011) and integrate auditory and visual information optimally (Moro et al., 2013) compared with binocular and eye-patched viewing controls. Structurally, people with one eye have a less severe decrease in volume of the lateral geniculate nucleus contralateral to the remaining eye (Kelly et al., 2013). In addition, they have an asymmetry in medial geniculate body volume, larger in the left hemisphere compared to right, independent of which eye is removed (Moro et al., 2015). Given the existing audiovisual processing differences and structural changes in people with one eye, we investigated whether changes in functional activation for audiovisual stimuli are also present. Functional images were acquired with a 3T MRI scanner while participants were asked to observe a video of a speaker reading a story in an auditory only, visual only or audiovisual condition. A whole brain analysis to measure brain activity for auditory, visual and audiovisual stimuli was conducted in adults who had undergone early unilateral eye enucleation (surgical removal of one eye) compared to binocularly intact and eye-patched controls. People with one eye demonstrated increased activation in the auditory cortex contralateral to their removed eye for auditory stimuli and increased activation in the auditory, occipital and frontal cortex for audiovisual stimuli compared with controls. People with one eye demonstrated decreased activation in the occipital cortex contralateral to their removed eye for visual stimuli. In addition, they showed increased activation in the bilateral cuneus and fusiform gyrus ipsilateral to their removed eye for visual stimuli compared with controls. These functional changes, combined with changes in underlying neural structure provide evidence for compensatory reorganization for the loss of one half of visual inputs early in life.
Meeting abstract presented at VSS 2017