Trial-to-Trial Variability of Single Cells in Motor Cortices Is Dynamically Modified during Visuomotor Adaptation
Trial-to-Trial Variability of Single Cells in Motor Cortices Is Dynamically Modified during Visuomotor Adaptation
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DOI：
10.1523/jneurosci.3011-09.2009
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发表时间：
2009-12-02
影响因子：
5.3
通讯作者：
Vaadia, Eilon
中科院分区：
文献类型：
--
作者：
Mandelblat-Cerf, Yael;Paz, Rony;Vaadia, Eilon
所有大脑区域的神经元的尖峰活动都表现出变异性。尽管这种变异性的一部分可以被认为是对信息处理有害的噪声，但最近的研究结果表明，变异性也可能是有益的。特别是，有人认为运动系统的可变性允许探索可能的运动状态，因此可以促进学习和适应新环境。在这里，我们通过分析猴子适应新的旋转视觉运动任务的初级运动皮层（M1）和辅助运动区（SMA-proper）神经元的变异性来提供证据来支持这一观点。我们发现，学习过程中试验间的变异性增加，并表现出四个主要特征：（1）调制优先发生在运动目标已知的延迟期内，但在运动开始之前； (2) 学习结束时变异性恢复到初始水平； (3) 在首选运动方向接近于学习期间经历的运动方向的细胞中，变异性的增加更为明显； (4) SMA 学习的早期阶段出现了变异性的增加，而 M1 行为则达到了表现的稳定水平。这些结果与之前的发现高度一致，之前的发现表明神经元群体的变异性具有相似的趋势。总之，这些结果强化了这样的观点：单细胞变异性不仅仅是噪音，而且可能是感觉运动学习的基本机制的一个组成部分。
Neurons in all brain areas exhibit variability in their spiking activity. Although part of this variability can be considered as noise that is detrimental to information processing, recent findings indicate that variability can also be beneficial. In particular, it was suggested that variability in the motor system allows for exploration of possible motor states and therefore can facilitate learning and adaptation to new environments. Here, we provide evidence to support this idea by analyzing the variability of neurons in the primary motor cortex (M1) and in the supplementary motor area (SMA-proper) of monkeys adapting to new rotational visuomotor tasks. We found that trial-to-trial variability increased during learning and exhibited four main characteristics: (1) modulation occurred preferentially during a delay period when the target of movement was already known, but before movement onset; (2) variability returned to its initial levels toward the end of learning; (3) the increase in variability was more apparent in cells with preferred movement directions close to those experienced during learning; and (4) the increase in variability emerged at early phases of learning in the SMA, whereas in M1 behavior reached plateau levels of performance. These results are highly consistent with previous findings that showed similar trends in variability across a population of neurons. Together, the results strengthen the idea that single-cell variability can be much more than mere noise and may be an integral part of the underlying mechanism of sensorimotor learning.