The brains of those who are born blind make new connections in the absence of visual information, which results in enhanced compensatory abilities such as hearing, smell and touch, as well as cognitive functions such as memory and language, according to a new study led by Harvard Medical School researchers at Massachusetts Eye and Ear.
The report, published in PLOS One, describes for the first time structural, functional and anatomical changes in the brains of those born with blindness that are not present in normally sighted people.
“Our results demonstrate that the structural and functional neuroplastic brain changes occurring as a result of early ocular blindness may be more widespread than initially thought,” said lead author Corinna Bauer, HMS instructor of ophthalmology and a scientist at Schepens Eye Research Institute of Mass. Eye and Ear. “We observed significant changes not only in the occipital cortex, where vision is processed, but also areas implicated in memory, language processing and sensory motor functions.”
The researchers used MRI multimodal brain imaging techniques to reveal these changes in a group of 12 subjects who were born with or acquired profound blindness by the age of three. They compared the scans to a group of 16 normally sighted subjects, who were of the same age range. On the scans of those with early blindness, the team observed structural and functional connectivity changes, including evidence of enhanced connections that send information back and forth between areas of the brain not observed in the normally sighted group.
These connections appear to be unique to those with profound blindness, suggesting that the brain “rewires” itself in the absence of visual information to boost other senses. This is possible through the process of neuroplasticity, or the ability of our brains to naturally adapt to our experiences.
The researchers hope that increased understanding of these connections will lead to more effective rehabilitation efforts that will enable blind individuals to better compensate for the absence of visual information.
“Even in the case of being profoundly blind, the brain rewires itself in a manner to use the information at its disposal so that it can interact with the environment in a more effective manner,” said senior author Lotfi Merabet, HMS associate professor of ophthalmology and director of the Laboratory for Visual Neuroplasticity at the Schepens Eye Research Institute of Mass. Eye and Ear. “If the brain can rewire itself—perhaps through training and enhancing the use of other modalities like hearing and touch and language tasks such as braille reading—there is tremendous potential for the brain to adapt.”
Support for this study includes National Institutes of Health National Eye Institute grant R01 EY019924, the Low Vision Research Award from Research to Prevent Blindness and the Lions Clubs International Foundation.