Combined Adaptiveness of Specific Motor Cortical Ensembles Underlies Learning
Combined Adaptiveness of Specific Motor Cortical Ensembles Underlies Learning
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DOI：
10.1523/jneurosci.0076-10.2010
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发表时间：
2010-04-14
影响因子：
5.3
通讯作者：
Vaadia, Eilon
中科院分区：
文献类型：
--
作者：
Arce, Fritzie;Novick, Itai;Vaadia, Eilon
学习运动技能需要适应神经计算，这些计算可以产生或修改感觉和动作之间的联系。事实上，根据可用的感觉反馈，人类在适应动态负荷时可以使用不同的策略。在这里，我们研究了当猴子的手臂到达视觉目标并局部适应有或没有视觉轨迹反馈的卷曲力场时，运动皮质的神经活动是如何改变的。我们发现，一大群细胞的放电速率一直受到调制，这取决于它们的首选方向与学习到的运动方向的距离。新获得的活动遵循类余弦函数，在与扰动力相反的方向上增加最大，在相反方向上减少。结果，组合的神经元活动产生了一个适应的种群矢量。结果表明，这可以在不改变电池的调谐特性的情况下实现。然而，在没有视觉反馈的情况下，这种种群方向信号发生了变化；虽然调制的余弦模式保持不变，但调制细胞的种群分布在与不同轨迹形状一致的反馈中有所不同。最后，我们预测了基于类余弦调制的力场学习的泛化模式。这与已报道的人类泛化的特征一致，表明泛化功能与运动皮质中观察到的速率调制有关。总体而言，研究结果表明，新的神经元集合的联合激活可能以一种依赖于可用的感觉反馈和选择的策略的方式，为运动动力学内部模型的变化奠定基础。
Learning motor skills entails adaptation of neural computations that can generate or modify associations between sensations and actions. Indeed, humans can use different strategies when adapting to dynamic loads depending on available sensory feedback. Here, we examined how neural activity in motor cortex was modified when monkeys made arm reaches to a visual target and locally adapted to curl force field with or without visual trajectory feedback. We found that firing rates of a large subpopulation of cells were consistently modulated depending on the distance of their preferred direction from the learned movement direction. The newly acquired activity followed a cosine-like function, with maximal increase in directions that opposed the perturbing force and decrease in opposite directions. As a result, the combined neuronal activity generated an adapted population vector. The results suggest that this could be achieved without changing the tuning properties of the cells. This population directional signal was however altered in the absence of visual feedback; while the cosine pattern of modulation was maintained, the population distributions of modulated cells differed across feedback consistent with the different trajectory shapes. Finally, we predicted generalization patterns of force-field learning based on the cosine-like modulation. These conformed to reported features of generalization in humans, suggesting that the generalization function was related to the observed rate modulations in the motor cortex. Overall, the findings suggest that the new combined activation of neuronal ensembles could underlie the change in the internal model of movement dynamics in a way that depends on available sensory feedback and chosen strategy.