Blanchette Rockefeller Neurosciences Institute, West Virginia University, Morgantown, West Virginia 26506, USA.
J Neurosci. 2012 Sep 5;32(36):12472-87. doi: 10.1523/JNEUROSCI.2088-12.2012.
Rabbit eyeblink conditioning is a well characterized model of associative learning. To identify specific neurons that are part of the eyeblink premotor pathway, a retrograde transsynaptic tracer (pseudorabies virus) was injected into the orbicularis oculi muscle. Four time points (3, 4, 4.5, and 5 d) were selected to identify sequential segments of the pathway and a map of labeled structures was generated. At 3 d, labeled first-order motor neurons were found in dorsolateral facial nucleus ipsilaterally. At 4 d, second-order premotor neurons were found in reticular nuclei, and sensory trigeminal, auditory, vestibular, and motor structures, including contralateral red nucleus. At 4.5 d, labeled third-order premotor neurons were found in the pons, midbrain, and cerebellum, including dorsolateral anterior interpositus nucleus and rostral fastigial nucleus. At 5 d, labeling revealed higher-order premotor structures. Labeled fourth-order Purkinje cells were found in ipsilateral cerebellar cortex in cerebellar lobule HVI and in lobule I. The former has been implicated in eyeblink conditioning and the latter in vestibular control. Labeled neurons in anterior interpositus were studied, using neurotransmitter immunoreactivity to classify individual cell types and delineate their interconnectivity. Labeled third-order premotor neurons were immunoreactive for glutamate and corresponded to large excitatory projection neurons. Labeled fourth-order premotor interneurons were immunoreactive for GABA (30%), glycine (18%), or both GABA and glycine (52%) and form a functional network within anterior interpositus involved in modulation of motor commands. These results identify a complete eyeblink premotor pathway, deep cerebellar interconnectivity, and specific neurons responsible for the generation of eyeblink responses.
兔瞬目条件反射是一种具有特征的联想学习模型。为了确定参与瞬目运动前导通路的特定神经元，将逆行转导示踪剂（伪狂犬病毒）注入眼轮匝肌。选择 4 个时间点（3、4、4.5 和 5 d）来识别通路的连续节段，并生成标记结构的图谱。在 3 d，发现同侧面神经背外侧核中的一级运动神经元被标记。在 4 d，发现第二级运动前神经元位于网状核以及感觉三叉神经、听觉、前庭和运动结构中，包括对侧红核。在 4.5 d，发现标记的第三级运动前神经元位于脑桥、中脑和小脑，包括背外侧中间位核和前fastigial 核。在 5 d，标记揭示了更高阶的运动前结构。在小脑 VI 回和 I 回同侧小脑皮质中发现了标记的第四级浦肯野细胞。前者与瞬目条件反射有关，后者与前庭控制有关。对中间位的标记神经元进行了研究，使用神经递质免疫反应来对单个细胞类型进行分类，并描绘它们的相互连接。标记的第三级运动前神经元对谷氨酸呈免疫反应性，对应于大型兴奋性投射神经元。标记的第四级运动前中间神经元对 GABA（30%）、甘氨酸（18%）或 GABA 和甘氨酸（52%）呈免疫反应性，并在中间位形成一个参与运动指令调制的功能网络。这些结果确定了一个完整的瞬目运动前导通路、小脑深部的相互连接以及负责产生瞬目反应的特定神经元。
