Study shows early partial vision loss results in changes to auditory system

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People who have lost an eye early in life show changes not only in how the visual system is wired in their brain, but also in the wiring of their auditory sensory system.

The findings are the result of a new study led by York University and published in NeuroImage: Clinical.

Previous studies have shown that partial visual deprivation resulting from the surgical removal of an eye (monocular enucleation) results in structural white matter (wiring) changes in the visual system; however, this study investigated the structural white matter changes of the auditory system in adults who had an eye removed during childhood, when the brain was still developing. This allowed researchers to look at the long-term changes in brain structure. The findings were compared with results from control participants that have vision in two eyes.

The study, “Altered white matter structure in auditory tracts following early monocular enucleation,” was led by York University Professor Jennifer Steeves’ Perceptual Neuroscience Laboratory. The study was authored by Nikita Wong, Sara Rafique and Stefania Moro, who were grad students at the time of the research. Steeves, as well as Krista Kelly of the Retina Foundation of the Southwest, also contributed to the study.

Researchers state that unlike other forms of monocular (one eye) vision loss – such as a cataract in one eye – where binocular (two eye) visual input still remains, the surgical removal of an eye eliminates all visual input to the brain from that eye.

To see how this affects other sensory systems, specifically the auditory system, the team examined potential long-term consequences of losing an eye in childhood on white matter in the brain associated with auditory and audiovisual processing.

They looked at the wiring of auditory regions in the brain as well as the wiring that connects visual and auditory processing areas.

Participants with eye loss showed changes in how the auditory brain was wired and how it was connected to the visual brain.

“What was of interest was that some of the auditory wiring appeared more substantial than in controls and, further, the connections between the visual and auditory systems were more intact than expected, perhaps showing plasticity in the brain in order to adapt to partial vision loss,” said Steeves.