The brain’s response to sound is termed “frequency-following responses”, or FFRs. Clinicians use these as an assessor of hearing and speech capacity, helping them diagnose language disorders such as autism and dyslexia. FFR tests consist of a participant being played different sounds, with electrograph signals of their brain activity then being outputted. The more similar the neural response profile to the sound waves in the audio, the stronger the audio processing capacity.

The need for a deeper understanding

So far, monitoring FFR activity has forwarded understanding and treatment in the field enormously, though specificity is lacking. Studies show five to 10 percent of Americans have been diagnosed with a communication disorder, therefore improvement in diagnosis and treatment is badly needed.

“These tests can only tell us that something is off—but we don’t know what that ‘off’ is,” said Bharath Chandrasekaran, a scientist from the University of Pittsburgh. “Understanding the source and mechanism of FFR generation would allow for the development of specific markers of speech impairments, which would be instrumental in improving clinical diagnostics of auditory processing deficits.”

What part of our brain processes speech?

An interesting study has shed some light on exactly which areas FFRs come from when reacting to speech sounds. The study published in eNeuro, discovered both the cortex and brainstem were key players in creating and processing the signals. It was not previously known that the cortex played such a key role. With this new information, updated auditory models can be created and applied to a clinical setting.

Interpreting Mandarin

The experiment was carried out on organisms with a comparable hearing range and sensitivity; they included humans, guinea pigs, and a type of monkey called macaques. All participants, none of which spoke Mandarin Chinese, were played the “yi” syllable in the language. Intriguingly, a very similar neural response occurred across all species. “Recognizing the similarities between animal and human FFRs will allow us to study neural circuitry of sound processing in much greater detail,” stated lead author Nike Gnanateja Gurindapalli.

Source study: eNeuro – Frequency-following responses to speech sounds are highly conserved across species and contain cortical contributions