A SURVEY OF AUDITORY BRAIN-STEM NUCLEI IN THE CHICKEN (GALLUS-DOMESTICUS) WITH CYTOCHROME-OXIDASE HISTOCHEMISTRY

The chicken's auditory brainstem nuclei from the cochlear nuclei to the nuclei of the lateral leminiscus were studied with cytochrome oxidase histochemistry. A strong reactivity in the cochlear and laminar nuclei was confirmed. Additional structures displaying high activity levels include the superior olive and both partitions of the nucleus intermedius lemnisci lateralis. Unilateral cochlea removal led to a strong reduction of activity in the cochlear nuclei and the nucleus laminaris, whereas there was no remarkable effect in higher brainstem centers. After bilateral cochlea extirpation auditory structures still displayed higher enzyme levels than most other nuclei. These observations point to the extraordinary metabolic activity in the ascending auditory pathway which is largely independent of sensory input from the auditory nerve.