How shocking noises become long-term memories?

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Researchers from New York University’s Langone Medical Center have carried out a study in rats showing that a part of the brain acts as an amplifier, controlling how and where the brain stores and transforms sounds. Commenting the results of the study, senior author and neuroscientist Robert C. Froemke, Assistant Professor at NYU, explains, “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.” The group’s findings were published in the August volume of the journal Nature Neuroscience.

The team of 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 ensuring the rats associated the sound with food, the same sound was played at a much lower level. The locus coeruleus and auditory cortex still responded to the sound for a further two weeks, even at nearly imperceptible levels. This demonstrated that the memory of the sound and its associated reward was encoded by the locus coeruleus, helping to improve the rats’ ability to perceive the sound. In another series of tests, study rats were subjected to a specific sound and a set of mild shocks. It was found that when the shocks stopped, but the sound continued, the locus coeruleus response remained the same.

These initial findings need to be confirmed by further studies in animals and people but according to the authors, they should help to better understand how to improve hearing and memory abilities in people with hearing loss or possibly even Alzheimer’s disease, and how to alter or minimize memories involved in conditions like post-traumatic stress disorder.

Source: Futurity; Martins AR, et al. Coordinated forms of noradrenergic plasticity in the locus coeruleus and primary auditory cortex. Nature Neuroscience. 2015 Aug 24.

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