PDF(Pubmed)
Abstract：
The auditory cortex sends massive projections to the inferior colliculus, but the organization of this pathway is not yet well understood. Previous work has shown that the corticocollicular projection emanates from both layers 5 and 6 of the auditory cortex and that neurons in these layers have different morphological and physiological properties. It is not yet known in the mouse if both layer 5 and layer 6 project bilaterally, nor is it known if the projection patterns differ based on projection location. Using targeted injections of Fluorogold into either the lateral cortex or dorsal cortex of the inferior colliculus, we quantified retrogradely labeled neurons in both the left and right lemniscal regions of the auditory cortex, as delineated using parvalbumin immunostaining. After dorsal cortex injections, we observed that approximately 18-20% of labeled cells were in layer 6 and that this proportion was similar bilaterally. After lateral cortex injections, only ipsilateral cells were observed in the auditory cortex, and they were found in both layer 5 and layer 6. The ratio of layer 5:layer 6 cells after lateral cortex injection was similar to that seen after dorsal cortex injection. Finally, injections of different tracers were made into the two inferior colliculi, and an average of 15-17% of cells in the auditory cortex were double-labeled, and these proportions were similar in layers 5 and 6. These data suggest that (1) only the dorsal cortex of the inferior colliculus receives bilateral projections from the auditory cortex, (2) both the dorsal and lateral cortex of the inferior colliculus receive similar layer 5 and layer 6 auditory cortical input, and (3) a subpopulation of individual neurons in both layers 5 and 6 branch to innervate both dorsal cortices of the inferior colliculus.
摘要：
听觉皮层向下丘发送大量投影，但是这种途径的组织尚未得到很好的理解。先前的工作表明，皮质皮质突起从听觉皮层的第5层和第6层发出，并且这些层中的神经元具有不同的形态和生理特性。在鼠标中还不知道第5层和第6层是否都双向投影，也不知道投影图案是否基于投影位置而不同。使用向下丘的外侧皮质或背侧皮质靶向注射荧光金，我们量化了听觉皮层的左右左脑区域的逆行标记神经元，如使用小白蛋白免疫染色描绘的。背侧皮质注射后,我们观察到大约18-20％的标记细胞位于第6层，并且该比例在两侧相似。外侧皮质注射后,只在听觉皮层中观察到同侧细胞，在第5层和第6层中都发现了它们。外侧皮质注射后第5层：第6层细胞的比例与背侧皮质注射后相似。最后,在两个下丘注射不同的示踪剂，平均15-17%的听觉皮层细胞被双重标记，这些比例在第5层和第6层中相似。这些数据表明，（1）只有下丘的背皮质接受来自听觉皮质的双侧投射，(2)下丘背侧和外侧皮层接收相似的第5层和第6层听觉皮层输入，（3）第5层和第6层中的单个神经元亚群分支支配下丘的两个背侧皮质。
