School of Psychology, The University of Queensland, Brisbane, Australia.
Queensland Brain Institute, The University of Queensland, Brisbane, Australia.
Elife. 2023 Aug 15;12:e86439. doi: 10.7554/eLife.86439.
Visual field maps in human early extrastriate areas (V2 and V3) are traditionally thought to form mirror-image representations which surround the primary visual cortex (V1). According to this scheme, V2 and V3 form nearly symmetrical halves with respect to the calcarine sulcus, with the dorsal halves representing lower contralateral quadrants, and the ventral halves representing upper contralateral quadrants. This arrangement is considered to be consistent across individuals, and thus predictable with reasonable accuracy using templates. However, data that deviate from this expected pattern have been observed, but mainly treated as artifactual. Here, we systematically investigate individual variability in the visual field maps of human early visual cortex using the 7T Human Connectome Project (HCP) retinotopy dataset. Our results demonstrate substantial and principled inter-individual variability. Visual field representation in the dorsal portions of V2 and V3 was more variable than in their ventral counterparts, including substantial departures from the expected mirror-symmetrical patterns. In addition, left hemisphere retinotopic maps were more variable than those in the right hemisphere. Surprisingly, only one-third of individuals had maps that conformed to the expected pattern in the left hemisphere. Visual field sign analysis further revealed that in many individuals the area conventionally identified as dorsal V3 shows a discontinuity in the mirror-image representation of the retina, associated with a Y-shaped lower vertical representation. Our findings challenge the current view that inter-individual variability in early extrastriate cortex is negligible, and that the dorsal portions of V2 and V3 are roughly mirror images of their ventral counterparts.
人类早期外纹状区（V2 和 V3）的视野图传统上被认为形成了围绕初级视觉皮层（V1）的镜像代表。根据这个方案，V2 和 V3 相对于距状裂形成几乎对称的两半，背侧部分代表较低的对侧象限，腹侧部分代表较高的对侧象限。这种排列被认为在个体之间是一致的，因此可以使用模板以相当高的精度进行预测。然而，已经观察到偏离这种预期模式的数据，但主要被视为人为因素。在这里，我们使用 7T 人类连接组计划（HCP）视网膜图数据集系统地研究了人类早期视觉皮层视野图的个体变异性。我们的结果表明存在大量且有原则的个体间变异性。V2 和 V3 的背侧部分的视野代表比腹侧部分更具变异性，包括与预期镜像对称模式的实质性偏离。此外，左半球的视网膜图比右半球更具变异性。令人惊讶的是，只有三分之一的个体的左半球地图符合预期模式。视野符号分析进一步表明，在许多个体中，传统上被识别为背侧 V3 的区域在视网膜的镜像代表中表现出不连续性，与 Y 形的下垂直代表相关。我们的发现挑战了当前的观点，即早期外纹状皮层的个体间变异性可以忽略不计，并且 V2 和 V3 的背侧部分大致是腹侧对应部分的镜像。
