Extracortical descending projections to the rat inferior colliculus. 2002

V V Senatorov, and B Hu
Loeb Health Research Institute, Ottawa Hospital/University of Ottawa, 1053 Carling Avenue, Ottawa, ON, Canada K1Y 4E9. vsenator@helix.nih.gov

Feedback controlling is an important element in the sensory processing in the auditory system. It has been long recognized that the inferior colliculus (IC) sends direct ascending projections to the medial geniculate body (MGB), but receives feedback regulation from the auditory cortex. In the present study we probed the shorter extracortical projections to the IC, including the direct descending pathway from the MGB. In the rat, the fluorescence retrograde tracers Fluorogold, True Blue or Rhodamine latex microspheres were injected into the IC, and the auditory thalamus and surrounding regions were examined for fluorescent neurones. We did not find any retrograde labelling in the ventral division of the MGB. However, retrogradely labelled neurones were found in the medial and suprageniculate nuclei of the MGB. We also observed densely packed groups of fluorescent neurones in the peripeduncular nucleus and numerous labelled neurones in the nucleus of the brachium of the IC. The existence of a direct descending pathway to the IC from at least some auditory thalamic nuclei challenges the perception of the colliculo-thalamic relationship as one-way traffic and suggests more direct involvement of the auditory thalamus in the feedback regulation of the incoming acoustic signals.

UI MeSH Term Description Entries
D007245 Inferior Colliculi The posterior pair of the quadrigeminal bodies which contain centers for auditory function. Colliculus, Inferior,Brachial Nucleus of the Inferior Colliculus,Caudal Colliculus,Colliculus Inferior,Inferior Colliculus,Posterior Colliculus,Colliculi, Inferior,Colliculus Inferiors,Colliculus, Caudal,Colliculus, Posterior,Inferior, Colliculus,Inferiors, Colliculus
D008297 Male Males
D009434 Neural Pathways Neural tracts connecting one part of the nervous system with another. Neural Interconnections,Interconnection, Neural,Interconnections, Neural,Neural Interconnection,Neural Pathway,Pathway, Neural,Pathways, Neural
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011712 Pyramidal Tracts Fibers that arise from cells within the cerebral cortex, pass through the medullary pyramid, and descend in the spinal cord. Many authorities say the pyramidal tracts include both the corticospinal and corticobulbar tracts. Corticobulbar Tracts,Corticospinal Tracts,Decussation, Pyramidal,Corticobulbar Tract,Corticospinal Tract,Pyramidal Decussation,Pyramidal Tract,Tract, Corticobulbar,Tract, Corticospinal,Tract, Pyramidal,Tracts, Corticobulbar,Tracts, Corticospinal,Tracts, Pyramidal
D005246 Feedback A mechanism of communication within a system in that the input signal generates an output response which returns to influence the continued activity or productivity of that system. Feedbacks
D005829 Geniculate Bodies Part of the DIENCEPHALON inferior to the caudal end of the dorsal THALAMUS. Includes the lateral geniculate body which relays visual impulses from the OPTIC TRACT to the calcarine cortex, and the medial geniculate body which relays auditory impulses from the lateral lemniscus to the AUDITORY CORTEX. Lateral Geniculate Body,Medial Geniculate Body,Metathalamus,Corpus Geniculatum Mediale,Geniculate Nucleus,Lateral Geniculate Nucleus,Medial Geniculate Complex,Medial Geniculate Nucleus,Nucleus Geniculatus Lateralis Dorsalis,Nucleus Geniculatus Lateralis Pars Dorsalis,Bodies, Geniculate,Complex, Medial Geniculate,Complices, Medial Geniculate,Corpus Geniculatum Mediales,Geniculate Bodies, Lateral,Geniculate Bodies, Medial,Geniculate Body,Geniculate Body, Lateral,Geniculate Body, Medial,Geniculate Complex, Medial,Geniculate Complices, Medial,Geniculate Nucleus, Lateral,Geniculate Nucleus, Medial,Geniculatum Mediale, Corpus,Geniculatum Mediales, Corpus,Lateral Geniculate Bodies,Medial Geniculate Bodies,Medial Geniculate Complices,Mediale, Corpus Geniculatum,Mediales, Corpus Geniculatum,Nucleus, Geniculate,Nucleus, Lateral Geniculate,Nucleus, Medial Geniculate
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus
D020318 Rats, Long-Evans An outbred strain of rats developed in 1915 by crossing several Wistar Institute white females with a wild gray male. Inbred strains have been derived from this original outbred strain, including Long-Evans cinnamon rats (RATS, INBRED LEC) and Otsuka-Long-Evans-Tokushima Fatty rats (RATS, INBRED OLETF), which are models for Wilson's disease and non-insulin dependent diabetes mellitus, respectively. Long-Evans Rat,Long Evans Rats,Evans Rats, Long,Long Evans Rat,Long-Evans Rats,Rat, Long-Evans,Rats, Long Evans

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