Biane Jeremy S, Takashima Yoshio, Scanziani Massimo, Conner James M, Tuszynski Mark H
Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093.
Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093; Department of Neurobiology, University of California, San Diego, La Jolla, CA 92093; Howard Hughes Medical Institute, University of California, San Diego, La Jolla, CA 92093.
Neuron. 2016 Mar 16;89(6):1173-1179. doi: 10.1016/j.neuron.2016.02.001. Epub 2016 Mar 3.
Layer 5 neurons of the neocortex receive direct and relatively strong input from the thalamus. However, the intralaminar distribution of these inputs and their capacity for plasticity in adult animals are largely unknown. In slices of the primary motor cortex (M1), we simultaneously recorded from pairs of corticospinal neurons associated with control of distinct motor outputs: distal forelimb versus proximal forelimb. Activation of ChR2-expressing thalamocortical afferents in M1 before motor learning produced equivalent responses in monosynaptic excitation of neurons controlling the distal and proximal forelimb, suggesting balanced thalamic input at baseline. Following skilled grasp training, however, thalamocortical input shifted to bias activation of corticospinal neurons associated with control of the distal forelimb. This increase was associated with a cell-specific increase in mEPSC amplitude but not presynaptic release probability. These findings demonstrate distinct and highly segregated plasticity of thalamocortical projections during adult learning.
新皮层第5层神经元从丘脑接收直接且相对较强的输入。然而，这些输入在成年动物中的层内分布及其可塑性能力在很大程度上尚不清楚。在初级运动皮层（M1）切片中，我们同时记录了与不同运动输出控制相关的成对皮质脊髓神经元：远端前肢与近端前肢。在运动学习前激活M1中表达ChR2的丘脑皮质传入纤维，在控制远端和近端前肢的神经元的单突触兴奋中产生了等效反应，表明基线时丘脑输入是平衡的。然而，在熟练抓握训练后，丘脑皮质输入发生转移，偏向于激活与远端前肢控制相关的皮质脊髓神经元。这种增加与微小兴奋性突触后电流（mEPSC）幅度的细胞特异性增加有关，但与突触前释放概率无关。这些发现表明，在成年学习过程中，丘脑皮质投射具有独特且高度分离的可塑性。
