DIVERSE THALAMIC PROJECTIONS TO THE PREFRONTAL CORTEX IN THE RHESUS-MONKEY
DIVERSE THALAMIC PROJECTIONS TO THE PREFRONTAL CORTEX IN THE RHESUS-MONKEY
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DOI：
10.1002/cne.903130106
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发表时间：
1991-11-01
影响因子：
2.5
通讯作者：
DERMON, CR
中科院分区：
文献类型：
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作者：
BARBAS, H;HENION, THH;DERMON, CR
我们用逆行示踪剂(辣根过氧化物酶或荧光染料)研究了9只恒河猴丘脑前额叶区域的投射来源。我们的目的是确定与丘脑其他核团相比，内侧背核(MD)对这一投射系统有贡献的标记神经元的比例，并探讨丘脑投射与前额叶皮质特定构筑区域的关系。我们选择了基底腹侧(11区、12区和腹侧46区)和背侧(32区、14区、46区和8区)前额叶扇区进行研究。这一选择是基于我们之前的研究，这些研究表明这两个不同的建筑部分的皮质投影存在差异(Barbas，‘88；Barbas和Pandya，’89)。此外，对于每个区段，我们包括了具有不同构筑轮廓的区域，这也与前额叶皮质的连接模式有关。结果显示，MD包括大多数(超过80%)丘脑神经元投射到某些前额叶皮质(11、46和8区)；它对其他一些神经元(12区和32区)的贡献刚刚超过一半，而对14区的贡献不到三分之一。定向到基底腹侧和背侧前额叶的神经元群在MD内大部分是分离的：前者位于腹侧，后者位于背侧。然而，最引人注目的发现建立了丘脑起源和前额叶靶区的板层定义之间的关系。丘脑外侧前额叶皮质(46区和8区)的神经元大多起源于MD的小细胞和多种亚群，少数见于其他核团。相比之下，眼眶皮质和内侧皮质的板层分化程度较低，是MD的大细胞细分和许多其他边缘丘脑核团的靶点，包括中线和前部。因此，丘脑投射起源的地形图特异性随着靶区层状清晰度的增加而增加。此外，MD和内侧枕标记神经元的吻尾分布也因额叶前部靶区的板层界定程度不同而不同。MD的吻部和内枕投射到外侧前额叶皮质，尾部投射到眶和内侧边缘皮质。选择性破坏尾侧MD可以干扰人类和猴子的记忆过程，这表明丘脑-边缘前额叶环可能构成记忆的一条重要途径。
We studied the sources of thalamic projections to prefrontal areas of nine rhesus monkeys with the aid of retrograde tracers (horseradish peroxidase or fluorescent dyes). Our goal was to determine the proportion of labeled neurons contributing to this projection system by the mediodorsal (MD) nucleus compared to those distributed in other thalamic nuclei, and to investigate the relationship of thalamic projections to specific architectonic areas of the prefrontal cortex. We selected areas for study within both the basoventral (areas 11, 12, and ventral 46) and the mediodorsal (areas 32, 14, 46, and 8) prefrontal sectors. This choice was based on our previous studies, which indicate differences in cortical projections to these two distinct architectonic sectors (Barbas, '88; Barbas and Pandya, '89). In addition, for each sector we included areas with different architectonic profiles, which is also relevant to the connectional patterns of the prefrontal cortices.The results showed that MD included a clear majority (over 80%) of all thalamic neurons directed to some prefrontal cortices (areas 11, 46, and 8); it contributed just over half to some others (areas 12 and 32), and less than a third to area 14. Clusters of neurons directed to basoventral and mediodorsal prefrontal areas were largely segregated within MD: the former were found ventrally, the latter dorsally. However, the most striking findings establish a relationship between thalamic origin and laminar definition of the prefrontal target areas. Most thalamic neurons directed to lateral prefrontal cortices, which are characterized by a high degree of laminar definition (areas 46 and 8), originated in the parvicellular and multiform subdivisions of MD, and only a few were found in other nuclei. In contrast, orbital and medial cortices, which have a low degree of laminar differentiation, were targeted by the magnocellular subdivision of MD and by numerous other limbic thalamic nuclei, including the midline and the anterior. Thus topographic specificity in the origin of thalamic projections increased as the laminar definition of the target area increased. Moreover, the rostrocaudal distribution of labeled neurons in MD and the medial pulvinar also differed depending on the degree of the laminar definition of the prefrontal target areas. The rostral parts of MD and the medial pulvinar projected to the eulaminate lateral prefrontal cortices, whereas their caudal parts projected to orbital and medial limbic cortices. Selective destruction of caudal MD is known to disrupt mnemonic processes in both humans and monkeys, suggesting that this thalamic-limbic prefrontal loop may constitute an important pathway for memory.