Ascending inputs to, and internal organization of, cortical motor areas.
Ascending inputs to, and internal organization of, cortical motor areas.
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皮质运动区的上升输入和内部组织。
DOI：
10.1002/9780470513545.ch3
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Jones,EG
中科院分区：
文献类型：
--
作者：
Jones,EG
现代解剖学研究表明，与长期持有的教义相反，丘脑中似乎基本上没有丘脑、小脑、苍白球或实质黑质传入的汇聚。每个传入流都定义了自己的丘脑区域，通过将这些丘脑区域投射到分开的皮质区域，皮质下运动核团在皮质上的投射的独立性被保留了下来。只有脊丘脑系统似乎能同时接触到感觉和运动皮质。感觉运动丘脑的另一个组织原则是存在单独的解剖学和生理学定义的通道，由独立的传入输入和传递到皮质的神经元组组成。在躯体感觉中继核中，皮肤、深层、缓慢和快速适应通道的分离在丘脑和皮质的输入水平上是明显的。在运动系统中，来自每个深小脑核团的输入似乎在丘脑中彼此分离，而这些输入又来自前庭和脊髓丘脑系统。正如苍白球、黑质和小脑通路能够控制大脑皮层的运动前区和运动区一样，通过VLP的单独通道似乎也可以控制4区的不同功能单位。在大脑皮层本身，从3a区和3b区到4区的皮质连接的缺乏似乎表明，从这些区流出的信息在传输到4区之前被返回到1区和2区进行进一步处理，从而导致感觉汇聚的所有后果。据推测，这条路线足够快，感觉输入可以在短时间内到达第四区。尽管许多关于感觉运动皮质的内在结构和连通性的数据已经开始积累，但我们距离一个完整的线路图还很遥远。涉及丘脑传入的回路逐渐为人所知，存在的细胞的性质及其递质特征正从形态和免疫细胞化学研究中变得明显，以及特定细胞类型的轴突分支模式的信息，特别是GABA能细胞和兴奋性皮质细胞的信息。
Modern anatomical studies show that, contrary to the long‐held dogma, there appears to be essentially no convergence of lemniscal, cerebellar, pallidal, or substantial nigral afferents in the thalamus. Each afferent stream defines its own thalamic territory and, through the projection of these thalamic territories to separate cortical territories, the independence of the projections of subcortical motor nuclei upon the cortex is preserved. Only the spinothalamic system appears to gain access to both sensory and motor cortex.A further principle of organization in the sensorimotor thalamus is the presence of individual anatomically and physiologically defined channels, composed of separate afferent inputs and groups of neurons relaying to the cortex. In the somatic sensory relay nuclei the dissociation of cutaneous, deep slowly and rapidly adapting channels is clear‐cut in the thalamus and at the input level of the cortex. In the motor system, inputs from each of the deep cerebellar nuclei appear to be dissociated from one another in the thalamus and these in turn from the vestibular and spinothalamic systems. Just as pallidal, nigral and cerebellar pathways are in position to control separate premotor and motor areas of the cortex, so separate channels leading through VLp appear to be in a position to control separate functional units in area 4.Within the cortex itself the absence of corticocortical connections passing from areas 3a and 3b to area 4 appears to indicate that information flow out of these areas is back to areas 1 and 2 for further processing before transmission to area 4 with all the consequences that entails for sensory convergence. Presumably, this route is sufficiently rapid for sensory inputs to reach area 4 at short latency. Although many data are beginning to accrue on the intrinsic structure and connectivity of the sensorimotor cortex, we are still distant from a complete wiring diagram. Circuitry involving thalamic afferents is becoming known slowly and the nature of the cells that are present and their transmitter characteristics are becoming evident from morphological and immunocytochemical studies, along with information on the patterns of axonal ramification of specific cell types, especially of GABAergic cells and of excitatory corticocortical cells.