Pappas C L, Strick P L
J Comp Neurol. 1981 Aug 20;200(4):491-500. doi: 10.1002/cne.902000404.
Retrograde transport of HRP was employed to examine the pattern of callosal connections in the forelimb region of area 4 gamma in the cat. According to the conventional view, areas of the motor cortex which contain the representation of distal body parts neither send nor receive callosal fibers. If this is true, then an absence of callosal connections would define the sites of distal forelimb representation. Following multiple injections of HRP into the contralateral motor cortex, many labeled neurons were found in the forelimb region of area 4 gamma. However, within this region, two spatially separate areas were found where labeled neurons were either absent or present in very low density ("callosal holes"). The anatomically defined callosal holes corresponded in size, shape, and location to the physiologically defined digit zones. To provide direct evidence for this correspondence, retrograde HRP transport was combined with intracortical stimulation in the same animal. Small lesions placed in physiologically identified digit zones were located within the anatomically defined callosal holes. Thus, a double representation of the distal forelimb can be defined in area 4 gamma of the cat motor cortex using both anatomical and physiological methods.
采用辣根过氧化物酶（HRP）逆行运输法来研究猫4γ区前肢代表区的胼胝体连接模式。按照传统观点，运动皮层中包含远端身体部位代表区的区域既不发出也不接收胼胝体纤维。如果真是这样，那么胼胝体连接的缺失将界定远端前肢代表区的位置。在对侧运动皮层多次注射HRP后，在4γ区的前肢代表区发现了许多标记神经元。然而，在该区域内，发现了两个在空间上相互分离的区域，在这些区域标记神经元要么缺失，要么密度极低（“胼胝体孔”）。解剖学上确定的胼胝体孔在大小、形状和位置上与生理学上确定的手指区域相对应。为了为这种对应关系提供直接证据，在同一动物中将HRP逆行运输与皮质内刺激相结合。放置在生理学上确定的手指区域的小损伤位于解剖学上确定的胼胝体孔内。因此，利用解剖学和生理学方法，可以在猫运动皮层的4γ区界定远端前肢的双重代表区。
