Kim Seolmin, Park Jeongjun, Lee Joonyeol
Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, South Korea.
Department of Biomedical Engineering, Sungkyunkwan University, Suwon, South Korea.
Front Syst Neurosci. 2019 Nov 26;13:71. doi: 10.3389/fnsys.2019.00071. eCollection 2019.
The integration of sensory with top-down cognitive signals for generating appropriate sensory-motor behaviors is an important issue in understanding the brain's information processes. Recent studies have demonstrated that the interplay between sensory and high-level signals in oculomotor behavior could be explained by Bayesian inference. Specifically, prior knowledge for motion speed introduces a bias in the speed of smooth pursuit eye movements. The other important prediction of Bayesian inference is variability reduction by prior expectation; however, there is insufficient evidence in oculomotor behaviors to support this prediction. In the present study, we trained monkeys to switch the prior expectation about motion direction and independently controlled the strength of the motion stimulus. Under identical sensory stimulus conditions, we tested if prior knowledge about the motion direction reduced the variability of open-loop smooth pursuit eye movements. We observed a significant reduction when the prior expectation was strong; this was consistent with the prediction of Bayesian inference. Taking advantage of the open-loop smooth pursuit, we investigated the temporal dynamics of the effect of the prior to the pursuit direction bias and variability. This analysis demonstrated that the strength of the sensory evidence depended not only on the strength of the sensory stimulus but also on the time required for the pursuit system to form a neural sensory representation. Finally, we demonstrated that the variability and directional bias change by prior knowledge were quantitatively explained by the Bayesian observer model.
将感觉信息与自上而下的认知信号整合以产生适当的感觉运动行为，是理解大脑信息处理过程中的一个重要问题。最近的研究表明，眼动行为中感觉信号与高级信号之间的相互作用可以用贝叶斯推理来解释。具体而言，运动速度的先验知识会在平稳跟踪眼球运动的速度上引入偏差。贝叶斯推理的另一个重要预测是通过先验期望减少变异性；然而，在眼动行为中没有足够的证据支持这一预测。在本研究中，我们训练猴子改变对运动方向的先验期望，并独立控制运动刺激的强度。在相同的感觉刺激条件下，我们测试了关于运动方向的先验知识是否会降低开环平稳跟踪眼球运动的变异性。当先验期望强烈时，我们观察到变异性显著降低；这与贝叶斯推理的预测一致。利用开环平稳跟踪，我们研究了先验对跟踪方向偏差和变异性影响的时间动态。该分析表明，感觉证据的强度不仅取决于感觉刺激的强度，还取决于跟踪系统形成神经感觉表征所需的时间。最后，我们证明了先验知识引起的变异性和方向偏差变化可以由贝叶斯观察者模型进行定量解释。
