Huang Xin, Lisberger Stephen G
Howard Hughes Medical Institute, W. M. Keck Foundation Center for Integrative Neuroscience, and Department of Physiology, University of California, San Francisco, CA 94143, USA.
J Neurophysiol. 2009 Jun;101(6):3012-30. doi: 10.1152/jn.00010.2009. Epub 2009 Mar 25.
Smooth-pursuit eye movements are variable, even when the same tracking target motion is repeated many times. We asked whether variation in pursuit could arise from noise in the response of visual motion neurons in the middle temporal visual area (MT). In physiological experiments, we evaluated the mean, variance, and trial-by-trial correlation in the spike counts of pairs of simultaneously recorded MT neurons. The correlations between responses of pairs of MT neurons are highly significant and are stronger when the two neurons in a pair have similar preferred speeds, directions, or receptive field locations. Spike count correlation persists when the same exact stimulus form is repeatedly presented. Spike count correlations increase as the analysis window increases because of correlations in the responses of individual neurons across time. Spike count correlations are highest at speeds below the preferred speeds of the neuron pair and increase as the contrast of a square-wave grating is decreased. In computational analyses, we evaluated whether the correlations and variation across the population response in MT could drive the observed behavioral variation in pursuit direction and speed. We created model population responses that mimicked the mean and variance of MT neural responses as well as the observed structure and amplitude of noise correlations between pairs of neurons. A vector-averaging decoding computation revealed that the observed variation in pursuit could arise from the MT population response, without postulating other sources of motor variation.
即使多次重复相同的跟踪目标运动,平稳跟踪眼球运动仍存在变化。我们研究了这种跟踪变化是否可能源于颞中视觉区(MT)视觉运动神经元反应中的噪声。在生理学实验中,我们评估了同时记录的MT神经元对的尖峰计数的均值、方差和逐次相关性。MT神经元对的反应之间的相关性非常显著,并且当一对中的两个神经元具有相似的偏好速度、方向或感受野位置时,相关性更强。当反复呈现相同的精确刺激形式时,尖峰计数相关性仍然存在。由于单个神经元的反应随时间的相关性,随着分析窗口的增加,尖峰计数相关性增加。在低于神经元对偏好速度的速度下,尖峰计数相关性最高,并且随着方波光栅对比度的降低而增加。在计算分析中,我们评估了MT群体反应中的相关性和变化是否能够驱动观察到的跟踪方向和速度的行为变化。我们创建了模拟MT神经反应的均值和方差以及观察到的神经元对之间噪声相关性的结构和幅度的模型群体反应。矢量平均解码计算表明,观察到的跟踪变化可能源于MT群体反应,而无需假定其他运动变化来源。