Exploring the “Auditory Brain”
Researchers led by Professor Dr Tania Rinaldi Barkat from the Department of Biomedicine at the University of Basel have investigated the neuronal foundation of sound perception and sound discrimination in a challenging sound environment. The focus was on research into the auditory cortex—the “auditory brain,” that is, the area of the brain that processes acoustic stimuli. The resulting activity patterns stem from measurements in a mouse brain.
As is well known, the distinction between sounds becomes more difficult the closer they are in the frequency spectrum. Initially, the researchers assumed that additional noise could make such a hearing task even more difficult. However, the opposite was observed: The team was able to demonstrate that the brain’s ability to distinguish subtle tone differences improved when white noise was added to the background. Compared to a quiet environment, the noise thus facilitated auditory perception.
Noise Reduces Neuronal Activity
The data of the research group showed that white noise significantly inhibited the activity of the nerve cells in the auditory cortex. Paradoxically, this suppression of the neuronal excitation led to a more precise perception of the pure tones. “We found that less overlap occurred between populations of neurons during two separate tone representations,” explains Barkat. “As a result, the overall reduction in neuronal activity produced a more distinct tone representation.”
To confirm that the auditory cortex and not another area of the brain was responsible for neuronal activity and sound perception in the experiments, the researchers used the light-controlled technique of optogenetics. Their findings could possibly be used to improve auditory perception in situations where sounds are difficult to distinguish. According to Barkart, it is conceivable that cochlear implants could be equipped with an effect similar to white noise in order to improve the frequency resolution and thus the hearing result of their users.
Original paper: Christensen RK, Linden H, Nakamura M, Barkat TR. White noise background improves tone discrimination by suppressing cortical tuning curves. Cell Reports. 2019;29(7):2041-2053.e4.
Source: University of Basel, Cell Reports