DOES AGE AT COCHLEAR IMPLANTATION AFFECT THE DISTRIBUTION OF 2-DEOXYGLUCOSE LABEL IN CAT INFERIOR COLLICULUS

Cochlear implants are one treatment for children who are born deaf or become deaf before acquiring language. The question of optimum age for implantation arises. Using an animal model, we have studied the respo nse of the auditory brainstem to implantation at various ages. Neonata lly, pharmacologically deafened cats were implanted with a 4-electrode array in the left cochlea at ages from 100 to over 180 days. Eleven w ere chronically stimulated (1000 h if possible) with charge-balanced, biphasic current pulses; eight were unstimulated controls. In a termin al experiment, each animal received [(SC)-S-14]2-deoxyglucose i.v, pre ceding a 45-min stimulation program. The fraction of the right inferio r colliculus (IC) with a significant accumulation of label was calcula ted. If age at implantation were a significant factor in determining t he size of the responding region, the fraction would depend on the age ; this was nor observed. However, there was considerable variation in the IC fraction sizes within both stimulated and unstimulated groups, leading to the conclusion that there are factors other than age which determine the size of the responding region. Thus, for deaf children o f corresponding ages, age at implantation may not be of critical impor tance.