Department of Neurobiology, Weizmann Institute of Science Rehovot, Israel.
Front Syst Neurosci. 2011 Feb 23;5:4. doi: 10.3389/fnsys.2011.00004. eCollection 2011.
Neurons in the primary visual cortex receive subliminal information originating from the periphery of their receptive fields (RF) through a variety of cortical connections. In the cat primary visual cortex, long-range horizontal axons have been reported to preferentially bind to distant columns of similar orientation preferences, whereas feedback connections from higher visual areas provide a more diverse functional input. To understand the role of these lateral interactions, it is crucial to characterize their effective functional connectivity and tuning properties. However, the overall functional impact of cortical lateral connections, whatever their anatomical origin, is unknown since it has never been directly characterized. Using direct measurements of postsynaptic integration in cat areas 17 and 18, we performed multi-scale assessments of the functional impact of visually driven lateral networks. Voltage-sensitive dye imaging showed that local oriented stimuli evoke an orientation-selective activity that remains confined to the cortical feedforward imprint of the stimulus. Beyond a distance of one hypercolumn, the lateral spread of cortical activity gradually lost its orientation preference approximated as an exponential with a space constant of about 1 mm. Intracellular recordings showed that this loss of orientation selectivity arises from the diversity of converging synaptic input patterns originating from outside the classical RF. In contrast, when the stimulus size was increased, we observed orientation-selective spread of activation beyond the feedforward imprint. We conclude that stimulus-induced cooperativity enhances the long-range orientation-selective spread.
初级视皮层中的神经元通过各种皮层连接接收来自感受野（RF）外围的潜意识信息。在猫的初级视皮层中，已经报道了长程水平轴突优先与具有相似取向偏好的远距离柱结合，而来自更高视觉区域的反馈连接提供了更多样化的功能输入。为了理解这些横向相互作用的作用，描述它们的有效功能连接和调谐特性至关重要。然而，由于从未直接对其进行过特征描述，因此，无论其解剖学起源如何，皮质横向连接的整体功能影响尚不清楚。通过对猫 17 和 18 区的突触后整合进行直接测量，我们对视觉驱动的横向网络的功能影响进行了多尺度评估。电压敏感染料成像显示，局部定向刺激会引发一种定向选择性活动，该活动仍然局限于刺激的皮层前馈印迹。在超过一个超柱的距离处，皮质活动的横向扩展逐渐失去了其定向偏好，近似于空间常数约为 1mm 的指数。细胞内记录显示，这种定向选择性的丧失源于源自经典 RF 之外的会聚突触输入模式的多样性。相比之下，当刺激大小增加时，我们观察到激活的定向选择性扩展超出了前馈印迹。我们得出结论，刺激诱导的协同作用增强了远距离的定向选择性扩展。
