Dept. of Physiology, Feinberg School of Medicine, Northwestern Univ., 303 East Chicago Ave., Chicago, IL 60611, USA.
J Neurophysiol. 2013 Mar;109(6):1505-13. doi: 10.1152/jn.00372.2012. Epub 2012 Dec 28.
Control of reaching movements requires an accurate estimate of the state of the limb, yet sensory signals are inherently noisy, because of both noise at the receptors themselves and the stochastic nature of the information representation by neural discharge. One way to derive an accurate representation from noisy sensor data is to combine it with the output of a forward model that considers both the previous state estimate and the noisy input. We recorded from primary somatosensory cortex (S1) in macaques (Macaca mulatta) during both active and passive movements to investigate how the proprioceptive representation of movement in S1 may be modified by the motor command (through efference copy). We found neurons in S1 that respond to one or both movement types covering a broad distribution from active movement only, to both, to passive movement only. Those neurons that responded to both active and passive movements responded with similar directional tuning. Confirming earlier results, some, but not all, neurons responded before the onset of volitional movements, possibly as a result of efference copy. Consequently, many of the features necessary to combine the forward model with proprioceptive feedback appear to be present in S1. These features would not be expected from combinations of afferent receptor responses alone.
控制运动需要对肢体状态进行准确估计，但由于感受器本身的噪声以及神经放电对信息的随机表示，感觉信号本质上是有噪声的。从噪声传感器数据中得出准确表示的一种方法是将其与前向模型的输出相结合，该模型同时考虑了先前的状态估计和噪声输入。我们在猕猴的初级体感皮层（S1）中记录了主动和被动运动期间的神经元活动，以研究 S1 中运动的本体感受表示如何通过运动命令（通过传出副本）进行修改。我们发现 S1 中的神经元对一种或两种运动类型做出反应，这些运动类型的分布范围很广，从仅主动运动到两者都有，再到仅被动运动。那些对主动和被动运动都有反应的神经元表现出相似的方向调谐。与早期结果一致，一些（但不是全部）神经元在自主运动开始前就有反应，这可能是传出副本的结果。因此，似乎 S1 中存在将前向模型与本体感受反馈相结合所需的许多特征。仅从传入感受器反应的组合中是无法预测到这些特征的。
