Litvina Elizabeth Y, Chen Chinfei
Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Boston, 300 Longwood Avenue, Boston, MA 02115, USA; Program in Neuroscience, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
Department of Neurology, F.M. Kirby Neurobiology Center, Children's Hospital, Boston, 300 Longwood Avenue, Boston, MA 02115, USA; Program in Neuroscience, Harvard Medical School, 220 Longwood Avenue, Boston, MA 02115, USA.
Neuron. 2017 Oct 11;96(2):330-338.e5. doi: 10.1016/j.neuron.2017.09.037.
Precise connectivity between retinal ganglion cells (RGCs) and thalamocortical (TC) relay neurons is thought to be essential for the transmission of visual information. Consistent with this view, electrophysiological measurements have previously estimated that 1-3 RGCs converge onto a mouse geniculate TC neuron. Recent advances in connectomics and rabies tracing have yielded much higher estimates of retinogeniculate convergence, although not all identified contacts may be functional. Here we use optogenetics and a computational simulation to determine the number of functionally relevant retinogeniculate inputs onto TC neurons in mice. We find an average of ten RGCs converging onto a mature TC neuron, in contrast to >30 inputs before developmental refinement. However, only 30% of retinogeniculate inputs exceed the threshold for dominating postsynaptic activity. These results signify a greater role for the thalamus in visual processing and provide a functional perspective of anatomical connectivity data.
视网膜神经节细胞（RGCs）与丘脑皮质（TC）中继神经元之间精确的连接被认为是视觉信息传递所必需的。与这一观点一致，先前的电生理测量估计，1 - 3个RGCs汇聚到一个小鼠膝状TC神经元上。尽管并非所有已识别的接触都可能具有功能，但连接组学和狂犬病追踪技术的最新进展得出了更高的视网膜膝状体汇聚估计值。在这里，我们使用光遗传学和计算模拟来确定小鼠TC神经元上功能相关的视网膜膝状体输入数量。我们发现平均有十个RGCs汇聚到一个成熟的TC神经元上，这与发育精细化之前超过30个输入形成对比。然而，只有30%的视网膜膝状体输入超过了主导突触后活动的阈值。这些结果表明丘脑在视觉处理中发挥了更大的作用，并为解剖学连接数据提供了功能视角。
