Department of Psychology, Vanderbilt University, Nashville, Tennessee 37203, USA.
J Neurosci. 2011 Aug 10;31(32):11660-77. doi: 10.1523/JNEUROSCI.1777-11.2011.
The nodes of a parietal-frontal pathway that mediates grasping in primates are in anterior intraparietal area (AIP) and ventral premotor cortex (PMv). Nevertheless, multiple somatosensory and motor representations of the hand, in parietal and frontal cortex, respectively, suggest that additional pathways remain unrealized. We explored this possibility in macaque monkeys by injecting retrograde tracers into grasp zones identified in primary motor cortex (M1), PMv, and area 2 with long train electrical stimulation. The M1 grasp zone was densely connected with other frontal cortex motor regions. The remainder of the connections originated from somatosensory areas 3a and second somatosensory cortex/parietal ventral area (S2/PV), and from the medial bank and fundus of the intraparietal sulcus (IPS). The PMv grasp zone was also densely connected with frontal cortex motor regions, albeit to a lesser extent than the M1 grasp zone. The remainder of the connections originated from areas S2/PV and aspects of the inferior parietal lobe such as PF, PFG, AIP, and the tip of the IPS. The area 2 grasp zone was densely connected with the hand representations of somatosensory areas 3b, 1, and S2/PV. The remainder of the connections was with areas 3a and 5 and the medial bank and fundus of the IPS. Connections with frontal cortex were relatively weak and concentrated in caudal M1. Thus, the three grasp zones may be nodes of parallel parietal-frontal pathways. Differential points of origin and termination of each pathway suggest varying functional specializations. Direct and indirect connections between those parietal-frontal pathways likely coordinate their respective functions into an accurate grasp.
介导灵长类动物抓握的顶叶-额前通路的节点位于前顶内区（AIP）和腹侧运动前皮层（PMv）。然而，手在顶叶和额叶皮层中的多个体感和运动代表区域表明，其他通路仍未被发现。我们通过向初级运动皮层（M1）、PMv 和 2 区用长电刺激刺激确定的抓握区注射逆行示踪剂，在猕猴中探索了这种可能性。M1 抓握区与其他额叶皮层运动区紧密相连。其余的连接来自体感区域 3a 和第二体感皮层/顶叶腹侧区（S2/PV），以及顶内沟的内侧壁和底部（IPS）。PMv 抓握区也与额叶皮层运动区紧密相连，尽管不如 M1 抓握区紧密。其余的连接来自 S2/PV 和下顶叶的各个区域，如 PF、PFG、AIP 和 IPS 的尖端。2 区抓握区与体感区域 3b、1 和 S2/PV 的手部代表区域紧密相连。其余的连接是与区域 3a 和 5 以及 IPS 的内侧壁和底部。与额叶皮层的连接相对较弱，集中在 M1 的尾部。因此，这三个抓握区可能是并行顶叶-额前通路的节点。每条通路的起源和终止的差异点表明了不同的功能专业化。这些顶叶-额前通路之间的直接和间接连接可能会将其各自的功能协调到准确的抓握中。
