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Bin Zhang, Xiaofeng Tao, Guofu Shen, Janice Marie Wensveen, Earl L Smith, Yuzo M Chino; High heterogeneity in the receptive-field subunit maps of multiple nearby neurons in infant V2. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© ARVO (1962-2015); The Authors (2016-present)
We previously reported that chronic monocular defocus (-3D or -10D) between 3 and 12 weeks of age leads to amblyopia in monkeys, and that the receptive-field (RF) subunit maps of multiple nearby V2 neurons in these amblyopic monkeys are substantially different from each other. The magnitude of this map heterogeneity is highly correlated with the degree of binocular suppression in V2 and also with the depth of amblyopia of individual monkeys (reduced grating and vernier acuity). To gain insights into how these neural and perceptual anomalies may be developmentally linked, we compared the RF subunit maps of multiple nearby V2 neurons in ‘normal’ infant monkeys.
We recorded from multiple V2 neurons in anesthetized monkeys at 4 and 8 weeks of age. We employed dense white noise stimuli and standard unit recording methods. Spiking data were analyzed using Local Spectral Reverse Correlation (LSRC) to reveal the RF subunit maps of individual neurons. The heterogeneity of the subunit maps was quantified by calculating the differences in the preferred orientations and spatial frequencies between all pairs of subunits.
At 4 weeks of age, the subunit maps of nearby neurons were very different from each other although the subunit map of each neuron was normal (i.e., homogeneous). This heterogeneity in RF subunit maps between nearby neurons was similar to that found in adult amblyopic monkeys. However, this large heterogeneity of the subunit maps disappeared by 8 weeks of age.
We conclude that early binocular imbalance rapidly initiates robust binocular suppression in V1 and V2, which in turn disrupts the normal maturation of the intrinsic connections in V2 and/or the feedback connections from higher-order visual areas, resulting in the observed abnormally high heterogeneity of subunit maps between nearby multiple neurons. These results support the clinical opinion that the corrective procedures for binocular imbalance (hence reductions of binocular suppression) at the earliest possible age may be beneficial in preventing the emergence of amblyopia.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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