Morecraft Robert J, Herrick James L, Stilwell-Morecraft Kimberly S, Louie Jennifer L, Schroeder Clinton M, Ottenbacher Jonovan G, Schoolfield Matt W
Division of Basic Biomedical Sciences, The University of South Dakota School of Medicine, Vermillion, SD 57069, USA.
Brain. 2002 Jan;125(Pt 1):176-98. doi: 10.1093/brain/awf011.
Localization of the corticofugal projection in the corona radiata (CR) and internal capsule (IC) can assist in evaluating a patient's residual motor capacity following subtotal brain damage and predicting their potential for functional restitution. To advance our understanding of the organization of the corticofugal projection in this critical brain region, we studied the trajectories of the projection arising from six different cortical arm representations in rhesus monkeys. They included the arm representation of the primary (M1), ventral lateral pre- (LPMCv), dorsolateral pre- (LPMCd), supplementary (M2), rostral cingulate (M3) and caudal cingulate (M4) motor cortices. In the CR, each pathway was segregated as medial motor area fibres arched over the caudate and lateral motor area fibres arched over the putamen. In the IC, the individual corticofugal pathways were found to be widespread, topographically organized and partially overlapping. At superior levels of the IC, the corticofugal projection from the arm representation of M3 coursed through the middle and posterior portion of the anterior limb (ICa). The projection from M2 passed through the posterior portion of the ICa and the genu (ICg). The projection from LPMCv travelled through the genu and anterior portion of the posterior limb (ICp). The projection from LPMCd occupied the anterior portion of the ICp. The projection from M4 descended through the mid-portion of the ICp. Fibres from M1 also travelled in the ICp, positioned immediately posterior to the M4 projection. As each fibre system progressed inferiorly within the IC, all fibres shifted posteriorly to occupy the ICp. Within the ICp, the projections from M3, M2, LPMCv, LPMCd, M4 and M1 maintained their anterior to posterior orientation, respectively. M2, LPMCd and LPMCv fibres overlapped extensively, as did fibres from M4 and M1. Our data suggest that CR and superior capsular lesions may correlate with more favourable levels of functional recovery due to the widespread nature of arm representation. In contrast, the extensive overlap and comparatively condensed organization of arm representation at inferior capsular levels suggest that lesions seated inferiorly are likely to correlate with poorer levels of recovery of upper limb movement. Based on the relative density of corticospinal neurones associated with the motor areas studied, our findings also suggest that motor deficit severity is likely to increase as a lesion occupies progressively more posterior regions of the IC.
皮质传出投射在放射冠（CR）和内囊（IC）中的定位有助于评估脑部分损伤患者的残余运动能力，并预测其功能恢复的潜力。为了加深我们对这个关键脑区皮质传出投射组织的理解，我们研究了恒河猴六个不同皮质臂代表区发出的投射轨迹。它们包括初级运动皮质（M1）、腹外侧运动前皮质（LPMCv）、背外侧运动前皮质（LPMCd）、辅助运动皮质（M2）、吻侧扣带运动皮质（M3）和尾侧扣带运动皮质（M4）的臂代表区。在放射冠中，每条通路都被分隔开，内侧运动区的纤维呈弓形越过尾状核，外侧运动区的纤维呈弓形越过壳核。在内囊中，各个皮质传出通路分布广泛，呈拓扑学组织排列且部分重叠。在内囊较高水平，M3臂代表区的皮质传出投射穿过前肢的中部和后部（ICa）。M2的投射穿过ICa的后部和膝部（ICg）。LPMCv的投射穿过膝部和后肢的前部（ICp）。LPMCd的投射占据ICp的前部。M4的投射向下穿过ICp的中部。M1的纤维也走行于ICp，位于M4投射的紧邻后方。随着每个纤维系统在内囊内向下走行，所有纤维都向后移位，占据ICp。在ICp内，M3、M2、LPMCv、LPMCd、M4和M1的投射分别保持从前到后的排列方向。M2、LPMCd和LPMCv的纤维广泛重叠，M4和M1的纤维也是如此。我们的数据表明，由于臂代表区分布广泛，放射冠和上囊病变可能与更有利的功能恢复水平相关。相比之下，下囊水平臂代表区的广泛重叠和相对密集的组织表明，下囊部位的病变可能与上肢运动恢复较差相关。基于与所研究运动区相关的皮质脊髓神经元的相对密度，我们的研究结果还表明，随着病变逐渐占据内囊更靠后的区域，运动 deficit 严重程度可能会增加。
