Neuronal mechanisms of motion perception.
Neuronal mechanisms of motion perception.
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DOI：
10.1101/sqb.1990.055.01.065
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发表时间：
1990
期刊：
影响因子：
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通讯作者：
William T. Newsome;K. H. Britten;C. Salzman;J. Movshon
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文献类型：
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作者：
William T. Newsome;K. H. Britten;C. Salzman;J. Movshon
感觉神经生理学的一个长期问题是了解大脑皮层中的神经回路如何调节我们对视觉世界的感知。在某种程度上，这个问题之所以存在是因为它很难;视觉皮层中的回路在数量和复杂性上都是令人生畏的。然而，同样重要的是，对视觉系统的研究已经对皮层信息处理的本质产生了一系列令人着迷的见解。也许这些见解中最重要的是，与视网膜光感受器相反，单个皮层神经元选择性地对视觉场景的感知显著特征做出反应。例如，纹状皮质（或V1）中的神经元选择性地对局部轮廓的方向、视觉刺激的运动方向或落在两个视网膜不同位置的视觉轮廓做出反应（参见Hubel 1988）。这种性质的选择性神经元通常被认为与视觉感知的特定方面有关。例如，方向选择性神经元可以提供我们感知形状和形式的基本信息，方向选择性神经元可能在看到运动中发挥重要作用，方向选择性神经元可以介导立体深度的感觉。虽然神经元生理学和视觉感知之间的直接联系直观上很吸引人，但这种联系的证据通常是间接的（参见，例如，Teller 1984）。我们的研究目标是探索-以尽可能直接的方式-方向选择皮层神经元的生理特性和视觉运动感知之间的关系。所有的生理实验都是在恒河猴的中颞区（MT或V5）进行的，这是一个位于枕叶、顶叶和颞叶交界处附近的高阶视觉区，如图1所示。我们选择MT进行这些实验，因为它包含一个方便组织的方向选择神经元群体。MT中超过90%的神经元是方向选择性的（Zeki 1974; Maunsell and货车埃森1983），它们位于一系列“方向柱”中，系统地表示视野中每个点的运动方向（Albright et al. 1984）。因此，MT是一个合乎逻辑的网站，以调查方向选择神经元在运动知觉中的作用。我们的一般策略是在恒河猴中进行生理实验，这些恒河猴被训练来辨别随机点运动显示中的运动方向。在这样的实验中，我们可以同时监测生理事件和感知性能。精神障碍者的任务被设计成，好的表现取决于方向选择性皮层神经元所携带的信号。在研究过程中，我们提出了三个基本问题：（1）MT化学损伤后，方向辨别任务的表现是否受损？(2)皮质神经元是否对随机点显示中的运动信号足够敏感，从而解释心理物理性能？(3)我们能否通过电微刺激来操纵定向选择神经元的放电，从而影响对运动的知觉判断？这些问题的答案都是“是”（Newsome and Par 6 1988; Newsome et al. 1989 a，B; Salzman et al. 1990）;因此，我们得出结论，在我们的实验条件下，运动方向的知觉判断在很大程度上依赖于MT中方向选择神经元所携带的信息。
An enduring problem for sensory neurophysiology is to understand how neural circuits in the cerebral cortex mediate our perception of the visual world. In part, the problem endures because it is difficult; the circuits in visual cortex are formidable both in their number and in their complexity. Of equal importance, however, is that investigation of the visual system has yielded a stream of fascinating insights into the nature of cortical information processing. Perhaps foremost among these insights is that individual cortical neurons, in contrast to retinal photoreceptors, respond selectively to perceptually salient features of the visual scene. For example, neurons in striate cortex (or V1) respond selectively to the orientation of local contours, to the direction of motion of a visual stimulus, or to visual contours that fall on disparate locations in the two retinae (for review, see Hubel 1988). Selective neurons of this nature are often thought to be related to specific aspects of visual perception. For example, orientation-selective neurons could provide the basic information from which we perceive shape and form, direction-selective neurons might play a prominent role in seeing motion, and disparity-selective neurons could mediate the sensation of stereoscopic depth. Although straightforward links between neuronal physiology and visual perception are intuitively appealing, the evidence for such links is generally indirect (see, e.g., Teller 1984). The goal of our research is to explore--in as direct a manner as possible--the relationship between the physiological properties of direction-selective cortical neurons and the perception of visual motion. All of the physiological experiments were conducted in the middle temporal area (MT, or V5) of rhesus monkeys, a higher-order visual area that lies near the junction of the occipital, parietal, and temporal lobes as illustrated in Figure 1. We chose MT for these experiments because it contains a conveniently organized population of direction-selective neurons. More than 90% of the neurons in MT are direction-selective (Zeki 1974; Maunsell and Van Essen 1983), and they reside in a series of "direction columns" that systematically represents direction of motion at each point in the visual field (Albright et al. 1984). MT is thus a logical site to investigate the role of direction-selective neurons in motion perception. Our general strategy is to conduct physiological experiments in rhesus monkeys that are trained to discriminate the direction of motion in a random-dot motion display. In such experiments, we can simultaneously monitor physiological events and perceptual performance. The psychophysicat task is designed so that good performance depends on signals of the kind carried by direction-selective cortical neurons. We asked three basic questions during the course of the investigation: (1) Is performance on the direction discrimination task impaired following chemical lesions of MT? (2) Are cortical neurons sufficiently sensitive to the motion signal in the random-dot display to account for psychophysical performance? (3) Can we influence perceptual judgments of motion by manipulating the discharge of directionally selective neurons with electrical microstimulation? The answer to each of these questions is "yes" (Newsome and Par6 1988; Newsome et al. 1989a,b; Salzman et al. 1990); we therefore conclude that under the conditions of our experiments, perceptual judgments of motion direction rely heavily on information carried by direction-selective neurons in MT.