The Journal of Neuroscience, March 15, 2003, 23(6):2251
Responses of Neurons in the Middle Temporal Visual Area After
Long-Standing Lesions of the Primary Visual Cortex in Adult New World
Monkeys
Christine E.
Collins,
David C.
Lyon, and
Jon H.
Kaas
Department of Psychology, Vanderbilt University, Nashville,
Tennessee 37203
The retinotopic organization of the middle temporal visual area
(MT) was determined in six adult owl monkeys and one adult marmoset
69 d to 10 months after lesions of the dorsolateral primary visual
cortex (V1). The lesions removed were limited to extensive parts
of the representation of the lower visual quadrant in V1. Microelectrodes were used to record from neurons at numerous sites in
MT to determine whether parts of MT normally devoted to the lower
visual quadrant (1) were unresponsive to visual stimuli, (2) acquired
responsiveness to inputs from intact portions of V1, or (3) became
responsive to some other visually driven input such as a relay from the
superior colliculus via the pulvinar to MT. All monkeys (n = 6)
with moderate to moderately large lesions had unresponsive portions of
MT even after 10 months of recovery. These unresponsive regions were
retinotopically equivalent to the removed parts of V1 in normal
animals. Thus, there was no evidence for an alternative source of
activation. In addition, these results indicate that any retinotopic
reorganization of MT based on inputs from intact portions of V1 was not
extensive, yet neurons near the margins of responsive cortex may have
acquired new receptive fields, and the smallest 5° lesion of V1
failed to produce an unresponsive zone. Deprived portions of MT were not remarkably changed in histological appearance in cytochrome oxidase, Nissl, and Wisteria floribunda agglutinin
preparations. Nevertheless, some reduction in myelin staining and other
histological changes were suggested. We conclude that MT is highly
dependent on V1 for activation in these monkeys, and alternative
sources do not become effective over months when normal activation is absent. Additionally, remaining V1 inputs have only a limited capacity
to expand their activation territory into deprived portions of MT.
Key words:
area 17; V1; extrastriate cortex; lesion; MT; reorganization; plasticity
Copyright © 2003 Society for Neuroscience 0270-6474/03/2362251-14$05.00/0
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