Brain reorganization and response to unseen stimuli in blind people

Brain reorganization and response to unseen stimuli in blind people

In a condition known as blindsight, damage to the primary visual cortex (V1) on one side of the brain impairs conscious perception of visual stimuli that appear on the opposite side of space, yet patients respond appropriately to unseen stimuli.

Researchers combined behavioral and brain imaging techniques to examine how regions in the intact brain hemisphere might compensate for damage in the opposite hemisphere in a blindsight patient with left V1 damage. In a functional MRI experiment, the patient pressed a button to indicate the presence of a white square that appeared on either the right or left side of space in a series of trials.

Consciously perceived stimuli on the left side activated visually responsive brain regions confined to the right hemisphere. By contrast, unseen stimuli on the right side activated regions involved in processing visual information and planning movements in both hemispheres, in addition to the corpus callosum—a bundle of nerve fibers connecting the two hemispheres.

The findings suggest that behavioral responses of blindsight patients to unseen stimuli are mediated by enhanced activity in the intact hemisphere and increased communication between the hemispheres.
According to the authors, the study illuminates the neural mechanisms that might enable nonconscious abilities and functional recovery after brain damage.

http://www.pnas.org/content/early/2017/11/09/1714801114

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