Plasticity of tonotopic maps in auditory midbrain following partial cochlear damage in the developing chinchilla.
There is substantial reorganization of the midbrain (inferior colliculus) tonotopic map following neonatally induced partial cochlear lesions in the chinchilla. The most obvious feature of this remapping is a large "iso-frequency" region in the ventral sector of the central nucleus of inferior colliculus (ICC). Neurons in this region exhibit similar threshold and tuning properties, with a common characteristic frequency which corresponds to the high-frequency audiometric cutoff. This overrepresented frequency range also corresponds to the high-frequency border of the cochlear lesion. Alterations to the tonotopic map corresponding to lower frequencies, in more dorsal regions of ICC, depend on the extent and degree of the cochlear lesion. When there is minimal damage to apical (low-frequency) cochlear areas, the dorsal ICC has relatively normal frequency representations. With more extensive apical cochlear lesions there is a corresponding disruption of ICC tonotopic representation of the low frequencies. We conclude that the tonotopic map within the ICC can become (re)organized postnatally according to the abnormal pattern of neural activity from the auditory periphery. Similar reorganization can be expected to occur in human infants with a partial cochlear hearing loss from birth.
Harrison
R V
RV
Department of Otolaryngology, Hospital for Sick Children, Toronto, Canada. rvh@sickkids.on.ca
Ibrahim
D
D
Mount
R J
RJ
D000367:Age Factors; D000617:Aminoglycosides; D000818:Animals; D000900:Anti-Bacterial Agents; D001303:Auditory Cortex / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D002682:Chinchilla; D003051:Cochlea / Q000502:physiology / Q000648:ultrastructure; D003056:Cochlear Nerve / Q000254:growth & development / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D006319:Hearing Loss, Sensorineural / Q000139:chemically induced / Q000503:physiopathology; D007245:Inferior Colliculi / Q000254:growth & development / Q000502:physiology*; D008855:Microscopy, Electron, Scanning; D009410:Nerve Degeneration / Q000139:chemically induced / Q000503:physiopathology; D009473:Neuronal Plasticity / Q000502:physiology*; D013477:Superior Colliculi / Q000502:physiology
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents