The Journal of Neuroscience, May 15, 2000, 20(10):3884-3899
Progressive Transneuronal Changes in the Brainstem and Thalamus
after Long-Term Dorsal Rhizotomies in Adult Macaque Monkeys
Timothy M.
Woods1,
Catherine G.
Cusick2,
Tim
P.
Pons3,
Edward
Taub4, and
Edward G.
Jones1
1 Center for Neuroscience, University of California,
Davis, California 95616, 2 Department of Structural and
Cellular Biology, Tulane University Medical Center, New Orleans,
Louisiana 70112, 3 Department of Neurosurgery, Wake Forest
University School of Medicine, Winston-Salem, North Carolina 27157, and
4 Department of Psychology, University of Alabama at
Birmingham, Birmingham, Alabama 35294
This study deals with a potential brainstem and thalamic substrate
for the extensive reorganization of somatosensory cortical maps that
occurs after chronic, large-scale loss of peripheral input.
Transneuronal atrophy occurred in neurons of the dorsal column (DCN)
and ventral posterior lateral thalamic (VPL) nuclei in monkeys
subjected to cervical and upper thoracic dorsal rhizotomies for 13-21
years and that had shown extensive representational plasticity in
somatosensory cortex and thalamus in other experiments. Volumes of DCN
and VPL, number and sizes of neurons, and neuronal packing density were
measured by unbiased stereological techniques. When compared with the
opposite, unaffected, side, the ipsilateral cuneate nucleus (CN),
external cuneate nucleus (ECN), and contralateral VPL showed reductions
in volume: 44-51% in CN, 37-48% in ECN, and 32-38% in VPL. In the
affected nuclei, neurons were progressively shrunken with increasing
survival time, and their packing density increased, but there was
relatively little loss of neurons (10-16%). There was evidence for
loss of axons of atrophic CN cells in the medial lemniscus and in the
thalamus, with accompanying severe disorganization of the parts of the
ventral posterior nuclei representing the normally innervated face and
the deafferented upper limb. Secondary transneuronal atrophy in VPL,
associated with retraction of axons of CN neurons undergoing primary
transneuronal atrophy, is likely to be associated with similar
withdrawal of axons from the cerebral cortex and should be a powerful
influence on reorganization of somatotopic maps in the somatosensory cortex.
Key words:
plasticity; dorsal rhizotomy; transneuronal atrophy; dorsal column nuclei; ventral posterior lateral nucleus; stereology
Copyright © 2000 Society for Neuroscience 0270-6474/00/20103884-16$05.00/0
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