Auditory Processing Serving as a Powerful Biological Marker for Neurological Health

Today, people rely on their senses to experience the beauty of nature and life. The sense of sound is essential for listening to music, people, and the world around them, to be able to make everlasting memories. However, sound is more than just hearing; it is a precursor to the brain's overall health and function. What if auditory processing can be used to identify neurological health in people, whether it's genetic or man-made? 
 
Not long ago, I had the opportunity to listen to Dr. Krizman's research presentation on concussions and their relevance to auditory processing. Dr. Krizman's focus was on seeing if brain responses to sound can be a way of identifying concussions in children. This was done by studying fundamental frequency (F0), also known as the pitch cue and the frequency following response (FFR) to see its effects on auditory processing when have undergone a concussion. The first finding was the effect of concussions on neural timing. A concussion reduces the coordination of firing neurons, which is essential to sound encoding. When this happens, brain responses become less synchronous, signals are weaker and delayed, and sound representation is decreased. Then the FFR was measured to see how the auditory brainstem encodes sound. This showed measurable changes in the weakening of the F0 pitch, a reduced response, and less accurate response tracking of the sound. Through these findings, concussions affect the brain's ability to encode information at the subcortical level which can potentially be a precursor to identifying injury and recovery. 
 
A research study that I came across called "Neural coding of formant-exaggerated speech and nonspeech in children with and without autism spectrum disorders" by researchers Chen et al., discussed how children with Autism Spectrum Disorder (ASD) process speech sounds at the neural level. This was done by examining typically developing (TD) children and children with ASD using the measurements of the frequency following response (FFR) to determine how the auditory system encodes sound. The first finding was that children with ASD lacked the automatic enhancement of amplifying their speech compared to TD children. TD children's exaggerated speech had a stronger neural response, and their brainstem responses became more accurate compared to the ASD children's neural responses not significantly increasing and their brainstem response to enhance wasn't present. This reflects the influence on the cortex, where normally, its enhancement towards the brainstem responses to meaningful speech. In children with ASD, the lack of enhancement suggests that speech may not be prioritized neurologically in the same way as in TD children. Ultimately, this can lead to a potential downward impact on language development for children with ASD. From the neural differences, the research can suggest early sensory contributions to language and differences in communication in autism. 
 
Although Dr. Krizman's study focused on an injury and Dr. Chen's was developmental, both studies showed how the auditory system can be sensitive to brain disruption, leaving speech processing vulnerable. In children with concussions, there was delayed neural timing in the brainstem affecting the encoding of speech and in children with ASD, their exaggerated speech wasn't able to make the neural enhancement that the TD children were able to because of their altered cortical use. This ultimately shows a comparison of neurodevelopment to neurotrauma aswell as it's affects in areas of the brain leading to implications. Through these findings in children, it can be used to potentially catch indications of neurological health. 
 
Kraus, N., Thompson, E. C., Krizman, J., Cook, K., White-Schwoch, T., & LaBella, C. R. (2016). Auditory biological marker of concussion in children. Scientific Reports, 6(1). https://doi.org/10.1038/srep39009 
‌Chen, F., Zhang, H., Ding, H., Wang, S., Peng, G., & Zhang, Y. (2021). Neural coding of formant‐exaggerated speech and nonspeech in children with and without autism spectrum disorders. Autism Research, 14(7), 1357–1374. https://doi.org/10.1002/aur.2509