Cochlear implants and brain plasticity.
Cochlear implants have been implanted in over 110,000 deaf adults and children worldwide and provide these patients with important auditory cues necessary for auditory awareness and speech perception via electrical stimulation of the auditory nerve (AN). In 1942, Woolsey and Walzl presented the first report of cortical responses to localised electrical stimulation of different sectors of the AN in normal hearing cats, and established the cochleotopic organization of the projections to primary auditory cortex. Subsequently, individual cortical neurons in normal hearing animals have been shown to have well characterized input-output functions for electrical stimulation and decreasing response latencies with increasing stimulus strength. However, the central auditory system is not immutable, and has a remarkable capacity for plastic change, even into adulthood, as a result of changes in afferent input. This capacity for change is likely to contribute to the ongoing clinical improvements observed in speech perception for cochlear implant users. This review examines the evidence for changes of the response properties of neurons in, and consequently the functional organization of, the central auditory system produced by chronic, behaviourally relevant, electrical stimulation of the AN in profoundly deaf humans and animals.
Fallon
James B
JB
Bionic Ear Institute, 384-388 Albert Street, East Melbourne, VIC 3002, Australia. JFallon@BionicEar.org
Irvine
Dexter R F
DR
Shepherd
Robert K
RK
D000818:Animals; D001303:Auditory Cortex / Q000503:physiopathology*; D001306:Auditory Pathways / Q000503:physiopathology*; D001931:Brain Mapping; D019929:Cochlear Implantation; D003054:Cochlear Implants; D003056:Cochlear Nerve / Q000503:physiopathology*; D004558:Electric Stimulation; D034381:Hearing Loss / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D023421:Models, Animal; D009473:Neuronal Plasticity; D010898:Pitch Perception; D011571:Psychoacoustics; D013067:Speech Perception