How Trauma Affects Memory May Lead to Reversal of Hearing Loss

Groundbreaking research into how memories are formed may lead to a method to restore hearing loss.  Researchers at the NYU Langone Center published their findings in the August issue of Nature Neuroscience.  The researchers were looking at how loud sounds or trauma translate into memory connections in the brain as part of their studies on Post Traumatic Stress Disorder (PTSD).

The Fight or Flight Response and Hearing Connection

You’ve probably heard about “flight or fight” or the acute stress response.  This is the reaction that occurs in response to something that is terrifying. It developed as a response that helped primitive man survive encounters with fierce animals and other risks to life. Sudden noise or stress releases the hormone noradrenaline in the locus coeruleus area of the brain. 

As part of the study, researchers chemically stimulated the locus coeruleus in rats while they played a sound paired with a food reward. To ensure that the rats associated the sound with food, they played the same sound but more quietly after the initial training period.  The researchers recorded brain activity and found that the locus coeruleus and auditory cortex still responded to the sound, even when it was played at almost undetectable levels.

Robert C. Froemke, PhD, the senior study investigator explained to Science Daily, “Our study gives us deeper insight into the functions of the locus coeruleus as a powerful amplifier in the brain, controlling how and where the brain stores and transforms sudden, traumatizing sounds and events into memories.”  Dr. Froemke is a neuroscientist assistant professor at NYU Langone and the Skirball Institute of Biomolecular Medicine.

What Does This Mean for Hearing Loss?

Froemke says that the results clearly demonstrate that the memory of sound and its associated reward is encoded by the locus coeruleus, and that helped improve the rats’ ability to perceive the sound.

To put it in plain language, these researchers are the first to successfully improve hearing in rats by manipulating the brain. They believe the study results show how electrical impulses produced by a cochlear implant can better be used to improve hearing.

For his next steps, Froemke plans to investigate how information gets encoded in the locus coeruleus and then identify the cells that are activated by cochlear implants.

This doesn’t mean that hearing loss will be restored tomorrow, but it does mean that researchers are getting closer and closer to restoring hearing.  This research was funded in part by grants from the National Institute on Deafness and other Communication Disorders, a division of the US Department of Health and Human Services.