Department of Neurobiology, Northwestern University Evanston, IL, USA.
Department of Neurobiology, Northwestern University Evanston, IL, USA ; Interdepartmental Neuroscience Program, Northwestern University Evanston, IL, USA.
Front Neural Circuits. 2014 Mar 26;8:23. doi: 10.3389/fncir.2014.00023. eCollection 2014.
Visual neurons in the superior colliculus (SC) respond to both bright (On) and dark (Off) stimuli in their receptive fields. This receptive field property is due to proper convergence of On- and Off-centered retinal ganglion cells to their target cells in the SC. In this study, we have compared the receptive field structure of individual SC neurons in two lines of mutant mice that are deficient in retinotopic mapping: the ephrin-A knockouts that lack important retinocollicular axonal guidance cues and the nAChR-β2 knockouts that have altered activity-dependent refinement of retinocollicular projections. We find that even though the receptive fields are much larger in the ephrin-A knockouts, their On-Off overlap remains unchanged. These neurons also display normal level of selectivity for stimulus direction and orientation. In contrast, the On-Off overlap is disrupted in the β2 knockouts. Together with the previous finding of disrupted direction and orientation selectivity in the β2 knockout mice, our results indicate that molecular guidance cues and activity-dependent processes play different roles in the development of receptive field properties in the SC.
上丘中的视觉神经元在其感受野中对明（On）暗（Off）刺激均有反应。这种感受野特性归因于 On 中心和 Off 中心视网膜神经节细胞向其在 SC 中的靶细胞的适当会聚。在这项研究中，我们比较了两条突变小鼠系中单个 SC 神经元的感受野结构，这两条突变小鼠系在视定位图中存在缺陷：缺乏重要的视丘-上丘轴突导向线索的 Ephrin-A 敲除小鼠和改变了视丘-上丘投射的活性依赖性细化的 nAChR-β2 敲除小鼠。我们发现，尽管 Ephrin-A 敲除小鼠的感受野大得多，但它们的 On-Off 重叠保持不变。这些神经元对刺激方向和方位也表现出正常的选择性。相比之下，β2 敲除小鼠的 On-Off 重叠被破坏。结合β2 敲除小鼠中方向和方位选择性破坏的先前发现，我们的结果表明，分子导向线索和活性依赖性过程在 SC 中感受野特性的发展中起着不同的作用。
