Karami Alireza, Castaldi Elisa, Eger Evelyn, Piazza Manuela
Center for Mind/Brain Science, University of Trento, Rovereto, Italy.
Department of Neuroscience, Psychology, Pharmacology and Child Health, University of Florence, Florence, Italy.
Commun Biol. 2025 Jul 9;8(1):1029. doi: 10.1038/s42003-025-08395-z.
Visual numerosity, traditionally linked to the parietal cortex, is now thought to be represented across a broader cortical network, including early visual and associative areas in both streams. However, how numerosity is encoded relative to other visual features remains unclear. We conducted a whole-brain functional magnetic resonance imaging (fMRI) study with thirty-one adults performing a numerosity estimation task on visual sets varying in number, item size, total item area, field area, and density, ensuring tight stimulus control. Using model-based representational similarity analyses, we found numerosity represented independently of other visual properties in early visual areas and amplified in retinotopic and non-retinotopic associative regions across both streams. Dimensionality reduction of BOLD patterns revealed distinct geometries: a one-dimensional representation of numerical rank in early visual and ventral retinotopic areas, and a curved structure encoding rank and distance-to-endpoints in associative dorsal and ventral regions. These results demonstrate distinct neural coding schemes for numerosity across cortical regions.
传统上认为视觉数字感知与顶叶皮质有关，现在人们认为它在更广泛的皮质网络中得到表征，包括两个视觉信息流中的早期视觉区域和联合区域。然而，相对于其他视觉特征，数字感知是如何编码的仍不清楚。我们对31名成年人进行了一项全脑功能磁共振成像（fMRI）研究，他们在视觉集合上执行数字估计任务，这些视觉集合在数量、项目大小、项目总面积、视野面积和密度方面各不相同，以确保严格的刺激控制。使用基于模型的表征相似性分析，我们发现在早期视觉区域，数字感知独立于其他视觉属性进行表征，并在两个视觉信息流中的视网膜拓扑和非视网膜拓扑联合区域中得到增强。对血氧水平依赖（BOLD）模式进行降维分析揭示了不同的几何结构：在早期视觉区域和腹侧视网膜拓扑区域中，数字等级呈一维表征，而在联合背侧和腹侧区域中，编码等级和端点距离的呈曲线结构。这些结果表明，皮质区域对数字感知存在不同的神经编码方案。
