See how they hear: New study finds heightened hearing in blind mice

Vision loss may enhance the ability to differentiate between frequencies and pitches, which could make for better musicality, according to a recent study out of Johns Hopkins University.

The study, published Feb. 5 in Neuron, a biweekly scientific journal, found that blind mice were able to hear softer sounds and better distinguish different frequencies than they could when they could see. The study showed the majority of changes occurred in the auditory cortex after the mice were blinded.

The auditory cortex processes sound while the visual cortex processes visual cues. The animals were able to sense sound input coming from the periphery, meaning the neural connections in the auditory cortex became stronger, according to Hey-Kyoung Lee, associate professor in the Department of Neuroscience at Johns Hopkins University.

“We were able to see changes in the adult brain that indicates [it] can actually respond to changes in the sensory environment and … regulate their auditory processing,” Lee said.

Lee and her research team studied mice to determine how the brain adapts to losing vision. The mice were kept in the dark for a week to deprive them of vision, a method that only temporarily blinds them. The researchers then used open skull surgery to look at the auditory and visual cortex functions in the mice’s brains, Lee said.

The team collaborated with Dr. Patrick O. Kanold’s lab at the University of Maryland, where researchers recorded the neural responses of the blinded mice as they heard different sounds and tones, according to the study.

“What happens when you lose vision in the adult brain [is that it] alters the auditory area … [to] compensate for the loss of vision,” Lee said.

Similar changes have been shown in blind humans, according to Hilary Brodie, chairman of the Department of Otolaryngology and Neck Surgery at the University of California, Davis.

The part of the brain that would usually process visual information can be utilized for other functions, therefore enhancing other senses, he said.

This process of utilizing one part of the human brain for another function is called cross modal neuroplasticity, Brodie said.

Cross modal neuroplasticity may enable the visually impaired to be better at music, Brodie said, because other senses, like hearing, would be enhanced. A blind person could pay attention to more details in the music that other people would not keep listening for because their brain is focused on the task of hearing rather than trying to hear while simultaneously using other senses, he said.

“You’re just a little bit better at [using that sense],” Brodie said. “More brain is being allocated toward sensations other than vision.”

Nathan Bakkum, coordinator of musicology and assistant professor in Columbia’s Music Department, said he is hesitant to make a blanket statement about the loss of sight contributing to increased strength and sensitivity in a musician.

“Certainly in some cases it does,” Bakkum said. “Of course we have plenty of examples of great musicians who don’t have the benefit of sense of sight.”

There is a lot of meaningful visual information for performing musicians, Bakkum said. They are then able to manipulate their senses to focus their attention on hearing and that gives them a different kind of experience than when they focus on another sense, he said.

Based on the results of the study, Lee said she thinks the loss of vision may make a person a better musician. The change in the auditory cortex allowed the mice to hear softer sounds and to discern pitches more accurately.

The higher sound sensitivity and ability to differentiate pitches should increase a person’s musicality, Lee said.

“Music as an abstract art … is our personal and cultural context for sound,” Bakkum said.