Developmental plasticity of central auditory pathways: frequency representation after neonatal high frequency hearing loss

Cochleotopic (or tonotopic) organization is the systematic representation of the sensory epithelium of the cochlea within central auditory pathways including the cortex. This central mapping of the sensory surface is a feature of all sensory systems. The organization of these sensory maps can be significantly modified by abnormal patterns of excitatory input, particularly during early stages of development. The authors previous work has shown that ototoxic poisoning of the basal cochlear region (i.e., partial deafferentation) in newborn kittens results in the development of major changes to the frequency map in primary auditory cortex. Thus, regions of cortex which would normally contain neurons coding high frequencies (activity originating at cochlear base) has neurons tuned to lower frequencies. It appears that the establishment of cochleotopic maps in the auditory cortex depends on the integrity of the pattern of ascending input from the cochlea. In this study, they ask if this reorganization is a feature only of the auditory cortex or whether it also exists at the midbrain level (inferior colliculus)