Morecraft R J, Van Hoesen G W
Department of Anatomy, University of Iowa College of Medicine, Iowa City 52242.
J Comp Neurol. 1992 Aug 22;322(4):471-89. doi: 10.1002/cne.903220403.
We examined the distribution of cingulate projections to the somatotopically related parts of the primary (M1) and supplementary (M2) motor cortices of the monkey by using fluorescent dyes. Labeled neurons were found in layers 3, 5 and 6 of areas 24c and 23c and were heaviest following injections placed in M2. Projections to analogous somatotopic areas in M1 and M2 arose from similar cingulate regions. In area 24c, neurons projecting to the face area of M1 and M2 were located anteriorly, those to the hindlimb were located posteriorly, and neurons projecting to the forelimb area of M1 and M2 were located in between. In area 23c, neurons projecting to the forelimb area of M1 and M2 were located anteriorly and those to the hindlimb area of M1 and M2 were located posteriorly. The face area of M1 and M2 was not found to receive afferents from area 23c. In contrast to this discreteness, cingulate projections to Woolsey's axial representation of M1 were diffuse. The results support the presence of a separate and somatotopically organized cingulate motor cortex in area 24c. This is predicated on the facts that: (1) small injections of retrograde tracers placed in analogous somatotopic parts of M1 and M2 resulted in similar patterns of labeling within the electrophysiologically "excitable" portion of the anterior cingulate cortex, and (2) this organized topography infers somatotopy. Our data fail to support a somatotopically organized cingulate motor area in area 23c if the criterion of all body parts is demanded. By virtue of its anatomical location and its connectional relation to the spinal cord and isocortical motor fields on the one hand and to the limbic cortex on the other, area 24c may be considered as M3 and provide limbic influences at several levels of motor control.
我们运用荧光染料研究了猕猴扣带回向初级运动皮层（M1）和辅助运动皮层（M2）的躯体感觉相关部位的投射分布。在24c区和23c区的第3、5和6层发现了标记神经元，在M2区注射后标记最为密集。向M1和M2中类似躯体感觉区的投射源自相似的扣带回区域。在24c区，投射到M1和M2面部区域的神经元位于前部，投射到后肢的位于后部，而投射到M1和M2前肢区域的神经元位于两者之间。在23c区，投射到M1和M2前肢区域的神经元位于前部，投射到M1和M2后肢区域的位于后部。未发现M1和M2的面部区域接受来自23c区的传入纤维。与这种离散性不同，扣带回向伍尔西（Woolsey）的M1轴向代表区的投射是弥散的。这些结果支持在24c区存在一个独立的、按躯体感觉组织的扣带回运动皮层。这基于以下事实：（1）将逆行示踪剂小剂量注射到M1和M2的类似躯体感觉部位，在前扣带回皮层的电生理“可兴奋”部分内产生了相似的标记模式，以及（2）这种有组织的地形学推断出躯体感觉定位。如果要求所有身体部位都符合标准，我们的数据不支持23c区存在按躯体感觉组织的扣带回运动区。鉴于其解剖位置以及一方面与脊髓和等皮层运动区的连接关系，另一方面与边缘皮层的连接关系，24c区可被视为M3，并在运动控制的多个层面提供边缘系统的影响。
