Distinct Mechanisms for Size Tuning in Primate Visual Cortex
Distinct Mechanisms for Size Tuning in Primate Visual Cortex
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DOI：
10.1523/jneurosci.2268-11.2011
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发表时间：
2011-08-31
影响因子：
5.3
通讯作者：
Usrey, W. Martin
中科院分区：
文献类型：
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作者：
Briggs, Farran;Usrey, W. Martin
初级视觉皮层 (V1) 中的大多数神经元对刺激大小具有选择性，这一特性对于显着特征检测具有重要意义。尺寸选择性涉及建立神经元感受野的经典（中心）和超经典（周围）的神经元回路之间的动态相互作用。尽管人们对中心和周围亚基的调谐特性和刺激选择性了解很多，但对这些亚基如何相互作用以实现尺寸选择性的了解相对较少。为了解决这个问题，我们检查了警觉猴 V1 中类似分层处理阶段的两类锥体神经元的大小选择性的时间动态。这两类神经元由皮质第 6 层的神经元组成，并具有识别到外侧膝状核的投射。虽然两个神经元组都表现出相当水平的大小选择性，但它们调节的时间动态却显着不同。我们将每种细胞类型的大小调整曲线与一系列高斯和模型进行比较，发现具有快速传导轴突的神经元的感受野包含一个兴奋中心和一个具有相似起始时间的抑制周围。相比之下，具有慢速传导轴突的神经元除了周围成分之外还使用两个中心成分——早期的宽视野成分和增加活动的延迟窄视野成分。早期的宽视野成分代表了皮质神经元整合上下文信息的一种新机制。这些结果表明，皮层神经元的大小调节是通过多种独特的机制建立的，由神经元嵌入的丰富电路架构决定。
Most neurons in primary visual cortex (V1) are selective for stimulus size, a property with important implications for salient feature detection. Size selectivity involves dynamic interactions between neuronal circuits that establish the classical (center) and extraclassical (surround) of a neuron's receptive field. Although much is known about the tuning properties and stimulus selectivity of the center and surround subunits, relatively little is known about how these subunits interact to achieve size selectivity. To address this question, we examined the temporal dynamics of size selectivity in two classes of pyramidal neurons at similar hierarchical processing stages in V1 of alert monkeys. These two classes were comprised of neurons in cortical layer 6 with identified projections to the lateral geniculate nucleus. While both neuronal groups displayed comparable levels of size selectivity, the temporal dynamics of their tuning differed significantly. We compared the size tuning profiles of each cell type with a series of sum-of-Gaussian models and discovered that the receptive fields of neurons with fast-conducting axons contained an excitatory center and a suppressive surround with similar onset timing. In contrast, neurons with slow-conducting axons used two center components-an early wide-field component and a delayed narrow-field component that increased activity-in addition to the surround component. The early, wide-field component represents a novel mechanism for cortical neurons to integrate contextual information. These results demonstrate that size tuning in cortical neurons is established via multiple unique mechanisms, dictated by the rich circuit architecture in which neurons are embedded.