Howard Hughes Medical Institute, W.M. Keck Foundation Center for Integrative Neuroscience, Sloan-Swartz Foundation, University of California, San Francisco, San Francisco, California 94143, USA.
J Neurosci. 2012 Dec 5;32(49):17632-45. doi: 10.1523/JNEUROSCI.1163-12.2012.
Sensory-motor behavior results from a complex interaction of noisy sensory data with priors based on recent experience. By varying the stimulus form and contrast for the initiation of smooth pursuit eye movements in monkeys, we show that visual motion inputs compete with two independent priors: one prior biases eye speed toward zero; the other prior attracts eye direction according to the past several days' history of target directions. The priors bias the speed and direction of the initiation of pursuit for the weak sensory data provided by the motion of a low-contrast sine wave grating. However, the priors have relatively little effect on pursuit speed and direction when the visual stimulus arises from the coherent motion of a high-contrast patch of dots. For any given stimulus form, the mean and variance of eye speed covary in the initiation of pursuit, as expected for signal-dependent noise. This relationship suggests that pursuit implements a trade-off between movement accuracy and variation, reducing both when the sensory signals are noisy. The tradeoff is implemented as a competition of sensory data and priors that follows the rules of Bayesian estimation. Computer simulations show that the priors can be understood as direction-specific control of the strength of visual-motor transmission, and can be implemented in a neural-network model that makes testable predictions about the population response in the smooth eye movement region of the frontal eye fields.
感觉运动行为是由嘈杂的感觉数据与基于近期经验的先验知识的复杂相互作用产生的。通过改变猴子进行平滑追踪眼球运动的起始时的刺激形式和对比度，我们发现视觉运动输入与两个独立的先验知识相竞争：一个先验知识使眼球速度偏向于零；另一个先验知识根据目标方向的过去几天的历史来吸引眼球方向。这些先验知识会对由低对比度正弦光栅运动提供的微弱感觉数据的追踪起始速度和方向产生偏差。然而，当视觉刺激来自高对比度点的运动时，这些先验知识对追踪速度和方向的影响相对较小。对于任何给定的刺激形式，在追踪的起始阶段，眼速的均值和方差呈正相关，这与信号依赖噪声的预期相符。这种关系表明，追踪在运动准确性和变化之间进行了权衡，当感觉信号嘈杂时，两者都会减少。这种权衡是通过感觉数据和先验知识的竞争来实现的，这种竞争遵循贝叶斯估计的规则。计算机模拟表明，这些先验知识可以被理解为视觉运动传递强度的特定方向控制，并且可以在神经网络模型中实现，该模型可以对额眼区平滑眼球运动区域的群体反应做出可测试的预测。
