Cochlear implants can help restore hearing in patients with total deafness, but the response varies widely.
Some patients who receive the implant can understand conversations within hours after the implant is activated.
But others do not show much improvement even after several months.
A recent rat study published in Nature elucidates the neural mechanisms that restore hearing to cochlear implants.
The study provides pathways that could help improve the performance of these widely used medical devices.
Researchers custom-made cochlear implants for 16 deaf rats to study their brain activity patterns related to hearing recovery.
Like humans, the rats varied greatly in their response to the implants.
In this study, activation of the rat nucleus accumbens, a brainstem region associated with learning, predicted a positive response.
The observed inter-animal differences disappeared when the same brain region was artificially activated.
All rats stimulated in this way showed a response to sound within a few days of implantation.
Neurons in the nucleus accumbens produce and release the neuromodulatory substance norepinephrine, which subsequently affects the structure and function of multiple neural networks.
This brain “reconnection” is a key feature of learning.
When the cochlear implant is unsuccessful, the brain fails to reconnect itself, possibly because the nucleus accumbens is not sufficiently engaged.
The researchers believe that strategies to help engage this target region could help optimize the functioning of the neural implant device.