Locus coeruleus activity improves cochlear implant performance

• Published in: Nature (London) Vol. 613; no. 7943; pp. 317 - 323
• Main Authors: Glennon, Erin, Valtcheva, Silvana, Zhu, Angela, Wadghiri, Youssef Z., Svirsky, Mario A., Froemke, Robert C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 12.01.2023; Nature Publishing Group
• Subjects: 631/378/2619/1387; 631/378/2619/2618; Accuracy; Acoustics; Animals; Auditory Cortex - cytology; Auditory Cortex - physiology; Auditory Cortex - physiopathology; Auditory plasticity; Auditory system; Auditory tasks; Brain stem; Cochlea; Cochlear Implantation; Cochlear Implants; Cortex (auditory); Deafness; Deafness - physiopathology; Deafness - therapy; Hearing; Hearing - physiology; Humanities and Social Sciences; Learning; Learning - physiology; Locus coeruleus; Locus Coeruleus - cytology; Locus Coeruleus - physiology; multidisciplinary; Neural prostheses; Neuromodulation; Neuronal Plasticity; Neurons - physiology; Neuroplasticity; Noradrenaline; Norepinephrine; Norepinephrine - metabolism; Optogenetics; Photometry; Prosthetics; Rats; Reinforcement; Reward; Science; Science (multidisciplinary); Sensory stimulation; Transplants & implants
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-022-05554-8

Cochlear implants (CIs) are neuroprosthetic devices that can provide hearing to deaf people 1 . Despite the benefits offered by CIs, the time taken for hearing to be restored and perceptual accuracy after long-term CI use remain highly variable 2 , 3 . CI use is believed to require neuroplasticity in the central auditory system, and differential engagement of neuroplastic mechanisms might contribute to the variability in outcomes 4 – 7 . Despite extensive studies on how CIs activate the auditory system 4 , 8 – 12 , the understanding of CI-related neuroplasticity remains limited. One potent factor enabling plasticity is the neuromodulator noradrenaline from the brainstem locus coeruleus (LC). Here we examine behavioural responses and neural activity in LC and auditory cortex of deafened rats fitted with multi-channel CIs. The rats were trained on a reward-based auditory task, and showed considerable individual differences of learning rates and maximum performance. LC photometry predicted when CI subjects began responding to sounds and longer-term perceptual accuracy. Optogenetic LC stimulation produced faster learning and higher long-term accuracy. Auditory cortical responses to CI stimulation reflected behavioural performance, with enhanced responses to rewarded stimuli and decreased distinction between unrewarded stimuli. Adequate engagement of central neuromodulatory systems is thus a potential clinically relevant target for optimizing neuroprosthetic device use. Behavioural studies with deafened rats show that locus coeruleus activity and plasticity are key to rapid adaptation to and long-term hearing performance with cochlear implants.