Department of Neuroscience, Neuroscience Training Program.
Department of Neuroscience.
J Neurosci. 2014 May 14;34(20):6822-33. doi: 10.1523/JNEUROSCI.3137-13.2014.
Neural circuits that translate sensory information into motor commands are organized in a feedforward manner converting sensory information into motor output. The superior colliculus (SC) follows this pattern as it plays a role in converting visual information from the retina and visual cortex into motor commands for rapid eye movements (saccades). Feedback from movement to sensory regions is hypothesized to play critical roles in attention, visual image stability, and saccadic suppression, but in contrast to feedforward pathways, motor feedback to sensory regions has received much less attention. The present study used voltage imaging and patch-clamp recording in slices of rat SC to test the hypothesis of an excitatory synaptic pathway from the motor layers of the SC back to the sensory superficial layers. Voltage imaging revealed an extensive depolarization of the superficial layers evoked by electrical stimulation of the motor layers. A pharmacologically isolated excitatory synaptic potential in the superficial layers depended on stimulus strength in the motor layers in a manner consistent with orthodromic excitation. Patch-clamp recording from neurons in the sensory layers revealed excitatory synaptic potentials in response to glutamate application in the motor layers. The location, size, and morphology of responsive neurons indicated they were likely to be narrow-field vertical cells. This excitatory projection from motor to sensory layers adds an important element to the circuitry of the SC and reveals a novel feedback pathway that could play a role in enhancing sensory responses to attended targets as well as visual image stabilization.
将感觉信息转化为运动指令的神经回路以顺馈的方式组织，即将感觉信息转化为运动输出。上丘（SC）遵循这种模式，因为它在将视网膜和视皮层的视觉信息转换为快速眼球运动（扫视）的运动指令方面发挥作用。从运动到感觉区域的反馈被假设在注意力、视觉图像稳定性和扫视抑制中发挥关键作用，但与顺馈通路相反，运动反馈到感觉区域受到的关注要少得多。本研究使用大鼠 SC 切片中的电压成像和膜片钳记录来测试从 SC 的运动层到感觉浅层的兴奋性突触通路的假设。电压成像显示，电刺激运动层可引起浅层的广泛去极化。在感觉层中，药理学分离的兴奋性突触电位在运动层中的刺激强度依赖性方式与顺行兴奋一致。在感觉层中的神经元进行膜片钳记录显示，在运动层中应用谷氨酸可引起兴奋性突触电位。反应神经元的位置、大小和形态表明它们可能是窄场垂直细胞。这种从运动到感觉层的兴奋性投射为 SC 的回路增加了一个重要的元素，并揭示了一种新的反馈通路，它可能在增强对注视目标的感觉反应以及视觉图像稳定方面发挥作用。
