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The Journal of Neuroscience, July 23, 2003, 23(16):6434-6442
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Topographic Plasticity in Primary Visual Cortex Is Mediated by Local Corticocortical Connections
Mike B. Calford,1,2
Layne L. Wright,1
Andrew B. Metha,1 and
Vivian Taglianetti2
1Psychobiology Laboratory, School of Psychology,
The Australian National University, ACT 0200, Australia, and
2Vision, Touch and Hearing Research Centre, The
University of Queensland, Queensland 4072, Australia
The placement of monocular laser lesions in the adult cat retina produces a
lesion projection zone (LPZ) in primary visual cortex (V1) in which the
majority of neurons have a normally located receptive field (RF) for
stimulation of the intact eye and an ectopically located RF (displaced to
intact retina at the edge of the lesion) for stimulation of the lesioned eye.
Animals that had such lesions for 14-85 d were studied under halothane and
nitrous oxide anesthesia with conventional neurophysiological recording
techniques and stimulation of moving light bars. Previous work suggested that
a candidate source of input, which could account for the development of the
ectopic RFs, was long-range horizontal connections within V1. The critical
contribution of such input was examined by placing a pipette containing the
neurotoxin kainic acid at a site in the normal V1 visual representation that
overlapped with the ectopic RF recorded at a site within the LPZ. Continuation
of well defined responses to stimulation of the intact eye served as a control
against direct effects of the kainic acid at the LPZ recording site. In six of
seven cases examined, kainic acid deactivation of neurons at the injection
site blocked responsiveness to lesioned-eye stimulation at the ectopic RF for
the LPZ recording site. We therefore conclude that long-range horizontal
projections contribute to the dominant input underlying the capacity for
retinal lesion-induced plasticity in V1.
Key words: retinal lesion; area 17; horizontal connections; adult brain plasticity; cortical reorganization; ectopic receptive fields
Received Jan. 17, 2003;
revised Apr. 24, 2003;
accepted Apr. 24, 2003.
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