Metabolic activity of the central auditory structures following prolonged deafferentation.
The goal of this work was to evaluate, using autoradiographic techniques, the effects of variable periods of deafness on resting and evoked metabolic activity in central auditory structures elicited by direct electrical cochlear nucleus (CN) stimulation. Thirty-five pigmented guinea pigs, divided into five groups, underwent acute implantation of bipolar electrodes in the CN. One group was not deafened and served as hearing controls. The other four groups were deafened using an established protocol of sequential kanamycin/ethacrynic acid treatment and were tested at 4 weeks, 9 weeks, 16 weeks, and 15 months after deafening. Threshold currents for eliciting evoked middle latency responses (EMLRs) with direct CN stimulation were not significantly different between hearing and deafened groups. Autoradiographic data showed progressive reduction of the evoked metabolic response with incremental periods of deafferentation. Nevertheless, central auditory structures remained responsive to direct electrical stimulation of the CN. These data indicate that direct CN stimulation remains capable of activating the auditory tract despite prolonged periods of deafness.
el-Kashlan
H K
HK
Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor.
Noorily
A D
AD
Niparko
J K
JK
Miller
J M
JM
D000818:Animals; D001306:Auditory Pathways / Q000378:metabolism / Q000503:physiopathology; D001309:Auditory Threshold / Q000502:physiology; D001345:Autoradiography; D001933:Brain Stem / Q000378:metabolism / Q000503:physiopathology; D002250:Carbon Radioisotopes; D003638:Deafness / Q000378:metabolism* / Q000503:physiopathology; D003847:Deoxyglucose / Q000378:metabolism*; D004056:Differential Threshold / Q000502:physiology; D004558:Electric Stimulation; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D006309:Hearing / Q000502:physiology; D007245:Inferior Colliculi / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D009847:Olivary Nucleus / Q000378:metabolism / Q000503:physiopathology; D011149:Pons / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors; D000159:Vestibulocochlear Nerve / Q000378:metabolism* / Q000503:physiopathology
D002250:Carbon Radioisotopes; D003847:Deoxyglucose