Project: Research project

Project Details


Experiments described in this proposal are designed to elucidate
the descending central auditory pathways which terminate in the
cochlear nucleus of a primate, the bush baby (Galago
crassicaudatus). In order to discover and describe these pathways,
the retrograde tracer horseradish peroxidase (HRP) will be
injected into first, the whole of, and then various subdivisions of
the cochlear nucleus. The resulting labeled neurons in the
brainstem will indicate the source of specific descending
projections, but not the actual target or the pathway to that
target. In order to determine the path and specific termination
areas of these descending projections, tritiated amino acids and
PHA-L will be injected into areas which contained HRP-labeled
neurons and their course followed to the ultimate destination in
terminal boutons of the descending auditory pathway.

Although these methods will describe the origin, course, and
destination of descending pathways to the cochlear nucleus, they
cannot describe the function of these pathways. Thus, the third
method of our neuroanatomical arsenal, the immunohistochemical
labeling of the inhibitory neurotransmitter, GABA, will provide
insight into how some of these descending pathways may influence
ascending auditory afferent input arriving in the cochlear nucleus
from the periphery. The experimental strategy of labeling GABA
terminals before and after lesions located at the source of
descending pathways to the cochlear nucleus will provide data as
to which, if any, of the descending terminals may provide
GABAergic input to cochlear nucleus.

The long-range objective of this proposed research is to elucidate
the mediating neuroanatomical connection between the central
auditory system and motor output pathways capable of controlling

Results of this research will provide information about descending
inhibitory influences on incoming sensory neural activity
significant for interpreting clinical auditory brainstem responses
from patients with centrally-located pathology.
Effective start/end date7/1/87 → …


  • National Institute on Deafness and Other Communication Disorders: $39,232.00
  • National Institute on Deafness and Other Communication Disorders


  • Medicine(all)
  • Neuroscience(all)


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