People who have been blind for most of their lives may develop better hearing abilities because their brains process sounds more consistently and reliably, rather than simply becoming more sensitive to different sound frequencies, a new study published in the Journal of Neuroscience has found. The research also found that sighted musicians may develop a similar ability through musical training, suggesting that different sensory experiences can influence how the brain processes sound. The study examined nine people who became blind before the age of two and 18 sighted individuals. Participants in both groups had varying levels of musical training, allowing researchers to assess the effects of both early-life blindness and musical experience on hearing.
Participants completed two hearing tasks. In the first, they had to detect a tone played against background noise. This helped researchers assess how the cochlea, the inner-ear structure responsible for processing sound frequencies, responded to different tones. In the second task, participants had to identify which of two tones had a higher pitch. This test also relied on the brain's ability to interpret auditory information. The researchers found that people with early-life blindness performed better than sighted participants only in the pitch discrimination task. This suggested that their enhanced hearing abilities could stem from changes in how the brain processes sound, rather than from differences in how the ears detect sound frequencies. The researchers also used a mathematical model to understand what drove the difference in performance. It showed that people with early-life blindness were better at distinguishing pitches because their auditory systems had lower levels of what scientists call "internal noise". Internal noise refers to how consistently the auditory system responds to the same sound over time. Lower internal noise means the brain processes sounds more reliably, making it easier to distinguish between similar sounds. The study found that sighted musicians also had lower internal noise and responded more consistently to sounds than participants who had neither early-life blindness nor extensive musical training.
The findings highlight the role of brain plasticity — the ability of the brain to adapt its responses based on experience. The researchers explained that the brain adjusts to information that becomes important through experience. This can happen when children learn to read or when adults develop the ability to identify different bird species. The study identifies internal noise as an important factor in this process. One possible explanation is that sensory experiences, including blindness and musical training, help the brain develop and refine templates for interpreting sound. The findings suggest that different experiences may improve hearing by making the brain's responses to sounds more consistent.
The researchers said the findings could eventually help develop training methods to improve people's auditory abilities. For instance, targeted training in recognising the location of sounds could help people beginning to lose their vision rely more on hearing to navigate their surroundings. However, several questions remain unanswered, including how much training is needed to produce meaningful changes in the brain and which aspects of auditory experience are most important. Researchers also want to understand whether the effects of brain plasticity differ depending on when a person loses their vision or begins musical training. The brain may have greater plasticity during early development, meaning sensory experiences could affect it differently in adulthood. The team plans to investigate whether the improved pitch discrimination observed among people with early-life blindness and sighted musicians also extends to more complex, everyday listening situations.
