Department of Physiology and Biophysics, University of Colorado School of Medicine, Aurora, Colorado.
Neuroscience Graduate Program, University of Colorado School of Medicine, Aurora, Colorado.
J Comp Neurol. 2020 Sep 1;528(13):2254-2268. doi: 10.1002/cne.24888. Epub 2020 Feb 29.
The intermediate and deep layers of the midbrain superior colliculus (SC) are a key locus for several critical functions, including spatial attention, multisensory integration, and behavioral responses. While the SC is known to integrate input from a variety of brain regions, progress in understanding how these inputs contribute to SC-dependent functions has been hindered by the paucity of data on innervation patterns to specific types of SC neurons. Here, we use G-deleted rabies virus-mediated monosynaptic tracing to identify inputs to excitatory and inhibitory neurons of the intermediate and deep SC. We observed stronger and more numerous projections to excitatory than inhibitory SC neurons. However, a subpopulation of excitatory neurons thought to mediate behavioral output received weaker inputs, from far fewer brain regions, than the overall population of excitatory neurons. Additionally, extrinsic inputs tended to target rostral excitatory and inhibitory SC neurons more strongly than their caudal counterparts, and commissural SC neurons tended to project to similar rostrocaudal positions in the other SC. Our findings support the view that active intrinsic processes are critical to SC-dependent functions, and will enable the examination of how specific inputs contribute to these functions.
中脑上丘的中间和深层（SC）是几个关键功能的关键部位，包括空间注意力、多感觉整合和行为反应。虽然已知 SC 整合来自各种脑区的输入，但由于缺乏特定类型的 SC 神经元的神经支配模式的数据，因此对这些输入如何有助于 SC 依赖的功能的理解进展受到阻碍。在这里，我们使用 G 缺失的狂犬病病毒介导的单突触追踪来鉴定中间和深层 SC 中的兴奋性和抑制性神经元的输入。我们观察到，与抑制性 SC 神经元相比，兴奋性 SC 神经元的投射更强、更多。然而，兴奋性神经元的一个亚群被认为介导行为输出，它们从更少的脑区接收较弱的输入，而不是兴奋性神经元的总体群体。此外，外在输入往往比它们的尾侧对应物更强烈地靶向 SC 的头侧和尾侧兴奋性和抑制性神经元，而连合 SC 神经元往往投射到另一个 SC 中的类似头侧和尾侧位置。我们的发现支持这样一种观点，即主动内在过程对 SC 依赖的功能至关重要，并且将能够检查特定输入如何有助于这些功能。
