The visual cortex that hears
Some blind individuals can perceive their surroundings by making sharp clicking sounds with their tongues and interpreting the returning echoes. This ability, called human echolocation, is a neurological phenomenon. Research from the Brain and Mind Institute at the University of Western Ontario shows that this skill fundamentally rewires the brain. Using functional magnetic resonance imaging (fMRI), researchers like Melvyn Goodale and Lore Thaler have showed that in expert echolocators, the brain's visual cortex—the area that processes light in sighted people—is recruited to "see" the world through sound.
The experiments were cleverly designed to isolate the brain's response to echoes. Scientists recorded the clicks and their faint returning echoes using tiny microphones placed in the ears of echolocators as they identified objects. These recordings were then played back to the individuals while they lay inside an fMRI scanner. The scans revealed that the calcarine cortex, part of the primary visual cortex, showed robust activity in response to the echoes. This same brain region showed no special activation in sighted people who listened to the same sounds. The auditory cortex, responsible for hearing, processed the sounds but did not show the specialized activity related to interpreting the spatial information contained in the echoes; that job was passed on to the repurposed visual cortex.