The Journal of Neuroscience, December 15, 2002, 22(24):10891-10897
Direct Projections from Cochlear Nuclear Complex to Auditory
Thalamus in the Rat
Manuel S.
Malmierca1,
Miguel A.
Merchán1,
Craig K.
Henkel2, and
Douglas L.
Oliver3
1 Laboratory for the Neurobiology of Hearing, Institute
for Neuroscience of Castilla y León and Faculty of Medicine,
University of Salamanca, 37007 Salamanca, Spain, 2 Wake
Forest University School of Medicine, Department of Neurobiology and
Anatomy, Winston-Salem, North Carolina 27157-1010, and
3 University of Connecticut Health Center, Department of
Neuroscience, Farmington, Connecticut 06030-3401
It is known that the dorsal cochlear nucleus and medial geniculate
body in the auditory system receive significant inputs from
somatosensory and visual-motor sources, but the purpose of such inputs
is not totally understood. Moreover, a direct connection of these
structures has not been demonstrated, because it is generally accepted
that the inferior colliculus is an obligatory relay for all ascending
input. In the present study, we have used auditory neurophysiology,
double labeling with anterograde tracers, and retrograde tracers to
investigate the ascending projections of the cochlear nuclear complex.
We demonstrate that the dorsal cochlear nucleus and the small cell cap
of the ventral cochlear nucleus have a direct projection to the medial
division of the medial geniculate body. These direct projections from
the cochlear nucleus complex bypass the inferior colliculus and are
widely distributed within the medial division of the medial geniculate,
suggesting that the projection is not topographic. As a nonlemniscal
auditory pathway that parallels the conventional auditory lemniscal
pathway, its functions may be distinct from the perception of sound.
Because this pathway links the parts of the auditory system with
prominent nonauditory, multimodal inputs, it may form a neural network
through which nonauditory sensory and visual-motor systems may
modulate auditory information processing.
Key words:
medial geniculate body; auditory pathways; lateral
lemniscus; brachium of the inferior colliculus; nonlemniscal pathway; double labeling; dextran; multimodal information processing
Copyright © 2002 Society for Neuroscience 0270-6474/02/222410891-07$05.00/0
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