Martin J H, Cooper S E, Hacking A, Ghez C
Center for Neurobiology and Behavior, Columbia University; and the New York State Psychiatric Institute, New York, New York 10032, USA.
J Neurophysiol. 2000 Apr;83(4):1886-99. doi: 10.1152/jn.2000.83.4.1886.
This study examined the effects of selective inactivation of the cerebellar nuclei in the cat on the control of multijoint trajectories and trajectory adaptation to avoid obstacles. Animals were restrained in a hammock and trained to perform a prehension task in which they reached to grasp a small cube of meat from a narrow food well. To examine trajectory adaptation, reaching was obstructed by placing a horizontal bar in the limb's path. Inactivation was produced by microinjection of the GABA agonist muscimol (0.25-1.0 microg in 1 microL saline). Fastigial nucleus inactivation produced a severe impairment in balance and in head and trunk control but no effect on reaching and grasping. Dentate inactivation slowed movements significantly and produced a significant increase in tip path curvature but did not impair reaching and grasping. Selective inactivation of the anterior and posterior interpositus nuclei did not impair grasping but severely decreased the accuracy of reaching movements and produced different biases in wrist and paw paths. Anterior interpositus inactivation produced movement slowing (wrist speed) and under-reaching to the food well. Wrist and tip paths showed anterior biases and became more curved. Also animals could no longer make anticipatory adjustments in limb kinematics to avoid obstructions but sensory-evoked corrective responses were preserved. Posterior interpositus inactivation produced a significant increase in wrist speed and overreaching. Wrist and tip paths showed a posterior bias and became more curved, although in a different way than during anterior interpositus inactivation. Posterior interpositus inactivation did not impair trajectory adaptation to reach over the obstacle. During inactivation of either interpositus nucleus, all measures of kinematic temporal and spatial variability increased with somewhat greater effects being produced by anterior interpositus inactivation. We discuss our results in relation to the hypothesis that anterior and posterior interpositus have different roles in trajectory control, related possibly to feed-forward use of cutaneous and proprioceptive inputs, respectively. The loss of adaptive reprogramming during anterior interpositus inactivation further suggests a role in motor learning. Comparison with results from our earlier motor cortical study shows that the distinctive impairments produced by inactivation of these two nuclei are similar to those produced by selective inactivation of different zones in the forelimb area of rostral motor cortex. Our findings are consistent with the hypothesis that there are separate functional output channels from the anterior and posterior interpositus nuclei to rostral motor cortex for distinct aspects of trajectory control and, from anterior interpositus alone, for trajectory adaptation.
本研究考察了猫小脑核选择性失活对多关节轨迹控制及轨迹适应以避开障碍物的影响。动物被限制在吊床中，并接受训练以执行一项抓握任务，即从狭窄的食物槽中抓取一小块肉。为了考察轨迹适应，通过在肢体路径中放置一根水平杆来阻碍伸手动作。通过微量注射GABA激动剂蝇蕈醇（在1微升生理盐水中注入0.25 - 1.0微克）来实现失活。顶核失活导致平衡以及头部和躯干控制严重受损，但对伸手抓握没有影响。齿状核失活显著减慢了动作，并使末端路径曲率显著增加，但并未损害伸手抓握。前间位核和后间位核的选择性失活并未损害抓握，但严重降低了伸手动作的准确性，并在腕部和爪子路径上产生了不同的偏差。前间位核失活导致动作减慢（腕部速度）以及伸向食物槽的距离不足。腕部和末端路径显示出向前的偏差且变得更弯曲。此外，动物不再能对肢体运动学进行预期调整以避开障碍物，但感觉诱发的纠正反应得以保留。后间位核失活导致腕部速度显著增加以及伸手过度。腕部和末端路径显示出向后的偏差且变得更弯曲，尽管其方式与前间位核失活时不同。后间位核失活并未损害越过障碍物伸手的轨迹适应。在任一内侧核失活期间，运动学时间和空间变异性的所有指标均增加，前间位核失活产生的影响稍大。我们结合以下假设来讨论我们的结果：前间位核和后间位核在轨迹控制中具有不同作用，可能分别与皮肤和本体感觉输入的前馈利用有关。前间位核失活期间适应性重新编程的丧失进一步表明其在运动学习中的作用。与我们早期运动皮层研究的结果相比表明，这两个核失活所产生的独特损伤类似于在嘴侧运动皮层前肢区域不同区域选择性失活所产生的损伤。我们的发现与以下假设一致：从前间位核和后间位核到嘴侧运动皮层存在独立的功能输出通道，用于轨迹控制的不同方面，并且仅从前间位核存在用于轨迹适应的通道。
