c-fos Immunoreactivity at the Auditory and Visual Cortex in Experimentally Induced Deafness in Guinea Pigs / 대한이비인후과학회지

ABSTRACT

BACKGROUND AND OBJECTIVES: Recently, functional studies for auditory cortex are being watched with interest in accordance with development of many radiologic equipments and surgical devices for sensorineural hearing loss. Moreover, it is well known that the function of central auditory pathway is essential for hearing rehabilitation. There are some papers that reported about the functional or metabolic changes of auditory cortex in deafness and in patients with cochlear implantation. The aim of this study was to investigate indirectly the metabolic changes of primary auditory cortex and visual cortex in the c-fos immunoreactivity in an experimentally induced permanent threshold shift animal model. MATERIALS AND METHOD: Ototoxic drugs (kanamycin and furosemide) and noise were used for the induction of permanent threshold shift. Cochlear damages were evaluated with auditory brainstem responses (ABR) and morphologic studies. The c-fos immunoreactivity was observed with a lapse of time after deafening. RESULTS: After the administration of ototoxic drugs and noise exposure, ABR threshold shifts were not recovered until after three months. Cochlear damages were observed in broad areas of cochlea. The c-fos immunoreactivity in the primary auditory cortex was increased during the acute period but it was decreased after one month. In addition, it was recovered again within the level of control three months later. In the visual cortex, increased and sustained immunoreactivities were observed after the drug and noise exposure. CONCLUSION: This result shows the plasticity of auditory cortex and possibility of some kinds of auditory-visual cross modal plasticity.