Differential impairments in reaching and grasping produced by local inactivation within the forelimb representation of the motor cortex in the cat.
Differential impairments in reaching and grasping produced by local inactivation within the forelimb representation of the motor cortex in the cat.
复制标题
猫前肢运动皮层局部失活导致伸手和抓握的差异性损伤。
DOI：
10.1007/bf00230201
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发表时间：
1993
影响因子：
2
通讯作者：
Ghez,C
中科院分区：
文献类型：
--
作者：
Martin,JH;Ghez,C
本研究分析了通过显微注射蝇蕈醇对5只猫前肢运动皮层（MCx，4γ区）内3个位点的可逆失活所产生的到达任务表现及其适应性修改的变化。两个位点位于外侧MCx，吻侧（RL-MCx）和尾侧（CL-MCx）到交叉沟的末端，其中皮质内微刺激（ICMS）产生最远端肌肉的收缩。第三个部位位于更内侧的乙状结肠前回（RM-MCx），ICMS主要产生更近端肌肉的收缩。这项任务要求动物把手伸进一个水平的目标井，位于他们面前的三个可能的高度之一，抓住并取回一小块食物。伸展的高度主要通过肘关节屈曲来实现。抓取主要包括手指屈曲，食物回收包括前臂旋后和肩部伸展。在一些试验中，在肢体的路径中放置障碍物，以评估动物自适应调整其响应轨迹的运动学特征的能力。在正常动物中，在第一次试验中与杆接触触发了短潜伏期的校正反应，允许爪子绕过杆。在随后的所有试验中，轨迹都经过调整，以防止与障碍物接触，安全裕度约为1厘米。失活在所有网站产生了一个缓慢的运动，延长和延长前肢姿势，并增加了初始肢体位置的变化。此外，RL-MCx的失活立即产生系统性的到达错误，包括高测量运动，以及抓握和食物取回受损。所有目标高度的远视程度相似，与轨迹控制的改变无关。在失活过程中，动物没有通过减少爪路径抬高来补偿远视，这表明运动规划或自适应控制存在缺陷。这一点通过发现在RL-MCx失活过程中避免杆接触的轨迹适应性受损得到证实。然而，由肢体与障碍物接触触发的短潜伏期纠正反应被保留了下来。CL-MCx的失活不会损害注射后立即瞄准、抓握或适应。然而，损伤发生后约1小时注射后，在那个时候模仿RL-MCx失活的影响。这种延迟表明药物间接作用于RL-MCx。RM-MCx的失活并没有损害远端肌肉的控制，但达到高。目标越高，测量值越小，这表明它是由弱点造成的。我们的研究结果表明，这两个吻侧区的前肢面积的MCx发挥更重要的作用，在规划和执行的扩展响应比尾部。我们假设：（1）运动减慢、前肢姿势改变、辨距不足、抓握和食物获取障碍是由于MCx中每个部位局部代表的肌肉控制缺陷所致;（2）仅由RL-MCx失活产生的瞄准和适应缺陷是由于通常确保运动准确性的感觉运动转换的基础整合机制被破坏所致。
This study analyzed changes in the performance of a reaching task and its adaptive modification produced by reversible inactivation of three sites within the forelimb representation of the motor cortex (MCx, area 4γ) in five cats by microinjections of muscimol. Two sites were located in the lateral MCx, rostral (RL-MCx) and caudal (CL-MCx) to the end of the cruciate sulcus, where intracortical microstimulation (ICMS) produced contraction of the most distal muscles. The third site was located more medially, in the anterior sigmoid gyrus (RM-MCx) where ICMS primarily produced contraction of more proximal muscles. The task required the animals to reach into a horizontal target well, located in front of them at one of three possible heights, to grasp and retrieve a small piece of food. The height of the reach was primarily achieved by elbow flexion. Grasping consisted primarily of digit flexion, and food retrieval consisted of forearm supination and shoulder extension. In some blocks of trials, an obstacle was placed in the path of the limb to assess the animal's ability to adaptively adjust the kinematic characteristics of their response trajectory. In normal animals, contact with the bar on the first trial triggered a corrective response at short latency that allowed the paw to circumvent the bar. On all subsequent trials, the trajectory was adapted to prevent contact with the obstacle, with a safety margin of about 1 cm. Inactivation at all sites produced a slowing of movement, a protracted and extended forelimb posture, and increased variability of initial limb position. In addition, inactivation of RL-MCx immediately produced systematic reaching errors, consisting of hypermetric movements, as well as impaired grasping and food retrieval. The degree of hypermetria was similar for all target heights and was not associated with alterations in trajectory control. During inactivation, animals did not compensate for the hypermetria by reducing paw path elevation, suggesting a defect in kinematic planning or in adaptive control. This was confirmed by finding that trajectory adaptation to avoid bar contact was impaired during RL-MCx inactivation. The short latency corrective response, triggered by contact of the limb with the obstacle was, however, preserved. Inactivation of CL-MCx did not impair aiming, grasping, or adaptation immediately after injection. However, impairments occurred after about 1 h postinjection, and at that time mimicked the effects of RL-MCx inactivation. This delay suggests that the drug was acting indirectly on the RL-MCx. Inactivation of RM-MCx did not impair the control of distal muscles, but the reaches became hypometric. The hypometria was greater for higher targets, suggesting that it resulted from weakness. Our results suggest that both rostral regions of the forelimb area of MCx play a more important role in the planning and execution of the prehension response than the caudal portion. We hypothesize that (1) the slowing of movement, forelimb postural changes, hypometria, and grasping and food retrieval impairments are due to defective control of muscles represented locally at each site in MCx and that (2) aiming and adaptation defects, which are produced only by RL-MCx inactivation, result from disruption of integrative mechanisms underlying sensorimotor transformations that normally assure movement accuracy.