Cochlear nuclei neuroplasticity after auditory nerve and cochlea removal

Hearing loss clearly alters the function and connectivity in auditory pathways in the brain. The effects of an auditory receptor lesion on the auditory pathway might be linked to the absence of peripheral stimulation on the first level of the auditory pathway (cochlear nuclei, CN). Loss of stimulation affects the pathway connectivity, at least in the CN, inducing the reorganization of the neural circuits. This reorganization may reduce the efficiency of some deafness therapies, including cochlear implants. Cochlea removal has been shown to be a good model for analysing neuroplasticity in the CN. Three main periods of degeneration and regeneration were found after cochlea removal. During the first week after cochlea removal, early effects included auditory nerve fibre degeneration, and the progressive degeneration of nerve endings on CN neurons. Some CN neurons degenerate. From the second week after cochlea removal a very limited and diffuse expression of GAP-43, a protein linked to developing or regenerat...