The frequency-following response, aka the auditory brainstem response to complex sounds, relates to the brain’s ability to respond to pitch. Those with concussion had an average 35% smaller response to pitch. And within the concussion group, those with the highest reported symptoms also had the smallest response to the fundamental frequency of speech. Not only was the response to pitch smaller, but it was also slower and less accurate in those participants who had suffered a concussion.
The researchers also found that as concussion symptoms abate, the response to pitch improved comparably. This proved their hypothesis that if sound processing is disrupted by concussion, it should also improve during the course of recovery.
The auditory system is at the nexus of the cognitive, sensory and limbic systems. Located in the midbrain, auditory processing is affected by both ascending and descending inputs from multiple neural systems outside of the auditory system. This makes it an ideal candidate for assessing effects of concussion that may occur anywhere in the brain. While concussions produce a variety of symptoms across multiple neural systems, this new assessment provides an objective measure that is not dependent on the subject’s effort or truthfulness in reporting.