Takemura A, Inoue Y, Kawano K, Quaia C, Miles F A
Neuroscience Section, Electrotechnical Laboratory, Ibaraki 305, Japan.
J Neurophysiol. 2001 May;85(5):2245-66. doi: 10.1152/jn.2001.85.5.2245.
Single-unit discharges were recorded in the medial superior temporal area (MST) of five behaving monkeys. Brief (230-ms) horizontal disparity steps were applied to large correlated or anticorrelated random-dot patterns (in which the dots had the same or opposite contrast, respectively, at the two eyes), eliciting vergence eye movements at short latencies [65.8 +/- 4.5 (SD) ms]. Disparity tuning curves, describing the dependence of the initial vergence responses (measured over the period 50-110 ms after the step) on the magnitude of the steps, resembled the derivative of a Gaussian, the curves obtained with correlated and anticorrelated patterns having opposite sign. Cells with disparity-related activity were isolated using correlated stimuli, and disparity tuning curves describing the dependence of these initial neuronal responses (measured over the period of 40-100 ms) on the magnitude of the disparity step were constructed (n = 102 cells). Using objective criteria and the fuzzy c-means clustering algorithm, disparity tuning curves were sorted into four groups based on their shapes. A post hoc comparison indicated that these four groups had features in common with four of the classes of disparity-selective neurons in striate cortex, but three of the four groups appeared to be part of a continuum. Most of the data were obtained from two monkeys, and when the disparity tuning curves of all the individual neurons recorded from either monkey were summed together, they fitted the disparity tuning curve for that same animal's vergence responses remarkably well (r(2): 0.93, 0.98). Fifty-six of the neurons recorded from these two monkeys were also tested with anticorrelated patterns, and all showed significant modulation of their activity (P < 0.005, 1-way ANOVA). Further, when all of the disparity tuning curves obtained with these patterns from either monkey were summed together, they too fitted the disparity tuning curve for that same animal's vergence responses very well (r(2): 0.95, 0.96). Indeed, the summed activity even reproduced idiosyncratic differences in the vergence responses of the two monkeys. Based on these and other observations on the temporal coding of events, we hypothesize that the magnitude, direction, and time course of the initial vergence velocity responses associated with disparity steps applied to large patterns are all encoded in the summed activity of the disparity-sensitive cells in MST. Latency data suggest that this activity in MST occurs early enough to play an active role in the generation of vergence eye movements at short latencies.
在五只行为猕猴的内侧颞上区（MST）记录了单神经元放电。对大的相关或反相关随机点图案（其中两眼处的点分别具有相同或相反的对比度）施加短暂（230毫秒）的水平视差阶跃，在短潜伏期[65.8±4.5（标准差）毫秒]引发辐辏眼动。视差调谐曲线描述了初始辐辏反应（在阶跃后50 - 110毫秒期间测量）对视差阶跃大小的依赖性，类似于高斯函数的导数，用相关和反相关图案获得的曲线具有相反的符号。使用相关刺激分离出具有视差相关活动的细胞，并构建了描述这些初始神经元反应（在40 - 100毫秒期间测量）对视差阶跃大小依赖性的视差调谐曲线（n = 102个细胞）。使用客观标准和模糊c均值聚类算法，根据视差调谐曲线的形状将其分为四组。事后比较表明，这四组与纹状皮层中四类视差选择性神经元中的四类具有共同特征，但四组中的三组似乎是一个连续体的一部分。大多数数据来自两只猕猴，当将从任何一只猕猴记录的所有单个神经元的视差调谐曲线相加在一起时，它们与同一只动物的辐辏反应的视差调谐曲线拟合得非常好（r²：0.93，0.98）。从这两只猕猴记录的56个神经元也用反相关图案进行了测试，所有神经元的活动都表现出显著调制（P < 0.005，单因素方差分析）。此外，当将用这些图案从任何一只猕猴获得的所有视差调谐曲线相加在一起时，它们也与同一只动物的辐辏反应的视差调谐曲线拟合得非常好（r²：0.95，0.96）。实际上，总和活动甚至再现了两只猕猴辐辏反应中的特异差异。基于这些以及关于事件时间编码的其他观察结果，我们假设与应用于大图案的视差阶跃相关的初始辐辏速度反应的大小、方向和时间进程都编码在MST中视差敏感细胞的总和活动中。潜伏期数据表明，MST中的这种活动发生得足够早，足以在短潜伏期的辐辏眼动产生中发挥积极作用。
