In humans, each hemisphere comprises an overlay of two visuotopic maps of the contralateral visual field, one from each eye. Is the capacity of the visual cortex limited to these two maps or are plastic mechanisms available to host more maps? We determined the cortical organization of the visual field maps in a rare individual with chiasma hypoplasia, where visual cortex plasticity is challenged to accommodate three hemifield maps. Using high-resolution fMRI at 7T and diffusion-weighted MRI at 3T, we found three hemiretinal inputs, instead of the normal two, to converge onto the left hemisphere. fMRI-based population receptive field mapping of the left V1-V3 at 3T revealed three superimposed hemifield representations in the left visual cortex, i.e. two representations of opposing visual hemifields from the left eye and one right hemifield representation from the right eye. We conclude that developmental plasticity including the re-wiring of local intra- and cortico-cortical connections is pivotal to support the coexistence and functioning of three hemifield maps within one hemisphere.

中文翻译：

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视交叉发育不全病例的三重视觉半场图

在人类中，每个半球都包含对侧视野的两个视觉图的叠加，每只眼睛一个。视觉皮层的容量是否仅限于这两个地图，或者是否可以使用塑料机制来承载更多地图？我们确定了一个罕见的具有交叉发育不良的个体的视野图的皮层组织，其中视觉皮层的可塑性受到挑战以适应三个半场图。使用 7T 的高分辨率 fMRI 和 3T 的弥散加权 MRI，我们发现三个半视网膜输入，而不是正常的两个，汇聚到左半球。基于 fMRI 的左侧 V1-V3 在 3T 的群体感受野映射揭示了左侧视觉皮层中三个叠加的半场表示，即 来自左眼的相对视觉半场的两种表示和来自右眼的一种右半场表示。我们得出结论，包括局部内部和皮质皮质连接的重新布线在内的发育可塑性对于支持一个半球内三个半球图的共存和功能至关重要。