A new study has revealed how exposure to brief trauma and sudden sounds form lasting memories in a specific region of the brain.
The research team said that they were able to chemically stimulate those biological pathways in the locus coeruleus, area of the brain best known for releasing the 'fight or flight' hormone noradrenaline, to heighten and improve the animals' hearing.
Senior study investigator Robert C. Froemke of the NYU Langone Medical Center said that their study gave them 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, traumatising sounds and events into memories.
The researchers said that these study results might help explain how electrical impulses, such as those produced by cochlear implants for the hearing impaired, could better be used to improve hearing, and how traumatising memories could be reshaped or dampened to lessen symptoms of PTSD.
In the study, researchers chemically stimulated the locus coeruleus in rats while simultaneously playing them a sound paired with a food reward.
After a two-week training period to ensure that the rats associated the sound with food, the same sound was played much more quietly.
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The researchers recorded activity in the same regions of their brain, as well as in the auditory cortex area responsible for interpreting sounds.
They found that the locus coeruleus and auditory cortex still responded to the sound, even at nearly imperceptible levels, for the subsequent and remaining two weeks of the experiments.
According to Froemke, the results clearly demonstrated that the memory of the sound and its associated reward was encoded by the locus coeruleus, which helped improve the rats' ability to perceive the sound.
The study is published in the journal Nature Neuroscience.