Can Sensory Loss Really Strengthen Other Senses?

A new study funded by the National Eye Institute suggests that lack of sight can lead to a sharpening of other senses like hearing. The study was powered by functional MRI (fMRI), a technique that measures brain activity by tracking blood flow changes. When an area of the brain is being used blood flow to the region spikes, which is recorded by fMRI scanners.

The team used the technique to record activity in the brains of blind participants. However instead of focusing on what parts of the brain were most active while listening, the team explored variations in cognitive sensitivity when exposed to slight differences in auditory frequency. The findings revealed that blind individuals have narrower neural "tuning" in the auditory cortex, which allows them to detect subtle differences in sound frequencies.

"We weren't measuring how rapidly neurons fire, but rather how accurately populations of neurons represent information about sound," explains Kelly Chang, lead author on one of the studies and graduate student in the University of Washington Department of Psychology.

Exploring neurological differences in blind individuals

The dual research papers were published in the Journal of Neuroscience and the Proceedings of the National Academy of Sciences and suggest that neurological differences could be responsible for the heightened sense of sound blind individuals.

"There's this idea that blind people are good at auditory tasks, because they have to make their way in the world without visual information. We wanted to explore how this happens in the brain," explains Ione Fine, senior author of both studies and Professor of Psychology at the University of Washington.

Study suggests brain can engage areas of the brain to heighten auditory signals

The second study explored how the brains of people who are born blind track moving auditory objects such as cars, footsteps or human voices. The findings suggest that the hMT+, an area of the brain used by sighted individuals to track moving visual objects, is actively engaged when blind individuals process auditory signals.

"This is the first study to show that blindness results in plasticity in the auditory cortex," says Fine. "This is important because this is an area of the brain that receives very similar auditory information in blind and sighted individuals. But in blind individuals, more information needs to be extracted from sound -- and this region seems to develop enhanced capacities as a result."

For the team, the findings help explain why blind people are equipped with a better sense of sound by recruiting different areas of the brain that aren’t necessarily associated with the auditory cortex.

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