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Cereb Cortex. 2019 Jun 18. pii: bhz096. doi: 10.1093/cercor/bhz096. [Epub ahead of print]

Altered Sensitivity to Motion of Area MT Neurons Following Long-Term V1 Lesions.

Hagan MA1,2,3, Chaplin TA1,2,3,4, Huxlin KR5, Rosa MGP1,2,3, Lui LL1,2,3.

Author information

1
Department of Physiology, Monash University, Clayton, VIC 3800, Australia.
2
Neuroscience Program, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia.
3
Australian Research Council, Centre of Excellence for Integrative Brain Function, Monash University Node, Clayton, VIC 3800, Australia.
4
Sainsbury Wellcome Centre for Neural Circuits and Behaviour, University College London, 25 Howland Street, London W1T 4JG, United Kingdom.
5
Flaum Eye Institute, University of Rochester, Rochester, NY 14642, USA.

Abstract

Primates with primary visual cortex (V1) damage often retain residual motion sensitivity, which is hypothesized to be mediated by middle temporal area (MT). MT neurons continue to respond to stimuli shortly after V1 lesions; however, experimental and clinical studies of lesion-induced plasticity have shown that lesion effects can take several months to stabilize. It is unknown what physiological changes occur in MT and whether neural responses persist long after V1 damage. We recorded neuronal responses in MT to moving dot patterns in adult marmoset monkeys 6-12 months after unilateral V1 lesions. In contrast to results obtained shortly after V1 lesions, we found that fewer MT neurons were direction selective, including neurons expected to still receive projections from remaining parts of V1. The firing rates of most cells increased with increases in motion strength, regardless of stimulus direction. Furthermore, firing rates were higher and more variable than in control MT cells. To test whether these observations could be mechanistically explained by underlying changes in neural circuitry, we created a network model of MT. We found that a local imbalance of inhibition and excitation explained the observed firing rate changes. These results provide the first insights into functional implications of long-term plasticity in MT following V1 lesions.

KEYWORDS:

MT; blindsight; marmoset monkey; motion; plasticity; vision

PMID:
31211357
DOI:
10.1093/cercor/bhz096

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