Brain Adapting to Changes Restore Hearing Loss

Does the brain adapt to hearing implants? The brain’s natural ability to adjust to a new situation can improve the efficacy of a cochlear implant that restores hearing loss.

Kickstarting the brain’s natural ability to adjust to new circumstances, or neuroplasticity improves how effectively a cochlear implant can restore hearing loss, a new study in deaf rats shows. The investigation may help explain the extreme variation in hearing improvements experienced by implant recipients.

Unlike hearing aids, which amplify, balance, and sharpen incoming sounds, cochlear implants send electrical signals that represent sounds directly to the brain.

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‘Brain flexibility may hasten hearing improvements from cochlear implants used in the treatment of hearing loss.’

Unfortunately, it can take time to understand the meaning of the signals. Past studies had shown that, while some cochlear implant users understand some speech hours after receiving their device, others required months or years to do so. However, the mechanisms that determine how quickly the brain can adjust to an implant have been unclear.

The new investigation led by researchers at NYU Langone Health in rats evaluated whether stimulating the locus coeruleus, a major site of neuroplasticity deep in the brainstem of mammals, improved how quickly they learned to use their devices.

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It showed that within just three days of receiving their implants, rodents given the extra boost could effectively complete tasks that required accurate hearing. By contrast, those without the stimulation needed up to 16 days to do so.

These findings suggest that differences in neuroplasticity, particularly in parts of the brain such as the locus coeruleus, may help explain why some cochlear implant users improve faster than others.

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In an earlier investigation, the research team found that electrically stimulating the locus coeruleus in rodents increases neuroplasticity and changes how the brain’s hearing system represents a sound.

However, the new study, published in the journal Nature, is the first to demonstrate that stimulating this brain region hastens hearing among cochlear implant recipients.

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For the investigation, they trained normal hearing rats to press a button after they heard a particular sound and to ignore the button if they heard a different tone. Once deafened, the rats were unable to complete the task. Then they were given cochlear implants and retrained to perform the same challenge by relying on the device.

Among the findings, the study showed that locus coeruleus activity changed dramatically as the rats learned to use their implants. At first, the brain region was most active when the animals received food after hearing the tone and pressing the correct button.

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As they learned to associate pressing the button with receiving the reward, activity instead peaked when they just heard the tones. Notably, the faster this change occurred, the faster the rats consistently succeeded at the task.

Researchers next plan to explore ways of stimulating the brain region in humans that do not require invasive surgery.

Source-Eurekalert