Burke-Cornell Medical Research Institute, White Plains, NY, USA.
Eur J Neurosci. 2010 Nov;32(10):1678-85. doi: 10.1111/j.1460-9568.2010.07440.x. Epub 2010 Oct 12.
Rats are used to model human corticospinal tract (CST) injury and repair. We asked whether rats possess the ability to orient their paw to the reaching target and whether the CST mediates this skill, as it does in primates. To test this ability, called preshaping, we trained rats to reach for pieces of pasta oriented either vertically or horizontally. We measured paw angle relative to the target and asked whether rats used target information attained before contact to preshape the paw, indicating feed-forward control. We also determined whether preshaping improved with practice. We then selectively lesioned the CST in the medullary pyramid contralateral to the reaching forepaw to test whether preshaping relies on the CST. Rats significantly oriented their paw to the pasta orientation before contact, demonstrating feed-forward control. Both preshaping and reaching efficiency improved with practice, while selective CST lesion abrogated both. The loss of preshaping was greatest for pasta oriented vertically, suggesting loss of supination, as seen with human CST injury. The degree of preshaping loss strongly correlated with the amount of skill acquired at baseline, suggesting that the CST mediates the learned component of preshaping. Finally, the amount of preshaping lost after injury strongly correlated with reduced retrieval success, showing an important functional consequence for preshaping. We have thus demonstrated, for the first time, preshaping in the rat and dependence of this skill on the CST. Understanding the basis for this skill and measuring its recovery after injury will be important for studying higher-level motor control in rats.
大鼠被用于模拟人类皮质脊髓束（CST）损伤和修复。我们想知道大鼠是否具有定向其爪子到达目标的能力，以及 CST 是否像在灵长类动物中那样介导这种技能。为了测试这种被称为预塑形的能力，我们训练大鼠伸手去拿垂直或水平定向的意面。我们测量爪子相对于目标的角度，并询问大鼠是否使用接触前获得的目标信息来预塑爪子，从而表明存在前馈控制。我们还确定了预塑形是否随练习而改善。然后，我们选择性地在与伸出的前爪相对的延髓锥体中损伤 CST，以测试预塑形是否依赖于 CST。大鼠在接触前明显地将爪子定向到意面的方向，表明存在前馈控制。预塑形和到达效率都随练习而提高，而选择性 CST 损伤则消除了两者。对于垂直定向的意面，预塑形的丧失最大，这表明存在旋前丧失，这与人类 CST 损伤相似。预塑形损失的程度与基线时获得的技能量强烈相关，这表明 CST 介导了预塑形的习得成分。最后，损伤后预塑形的丧失程度与检索成功率的降低密切相关，表明预塑形具有重要的功能后果。因此，我们首次在大鼠中证明了预塑形的存在，并证明了这种技能依赖于 CST。了解这种技能的基础，并测量其在损伤后的恢复情况，对于研究大鼠的高级运动控制非常重要。
