MOTION SELECTIVITY IN MACAQUE VISUAL-CORTEX .1. MECHANISMS OF DIRECTION AND SPEED SELECTIVITY IN EXTRASTRIATE AREA MT
MOTION SELECTIVITY IN MACAQUE VISUAL-CORTEX .1. MECHANISMS OF DIRECTION AND SPEED SELECTIVITY IN EXTRASTRIATE AREA MT
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DOI：
10.1152/jn.1986.55.6.1308
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发表时间：
1986-06-01
影响因子：
2.5
通讯作者：
WURTZ, RH
中科院分区：
文献类型：
--
作者：
MIKAMI, A;NEWSOME, WT;WURTZ, RH
在行为猕猴中颞叶视区（MT）单个神经元上研究了方向选择性和速度选择性的机制。当猴子注视一个固定的光点时，视觉刺激在神经元的感受野内以平滑和频闪的运动呈现。行为猴子的MT神经元的方向选择性，速度选择性和自发放电特性与先前在麻醉猴子中的研究中报道的相似。频闪运动刺激是以每次闪光之间的空间和时间间隔为特征的闪光序列。的空间和时间间隔系统地变化，使抑制和促进相互作用可以在两个首选和零方向进行研究。通过从频闪仪系列闪光引起的峰值放电率中减去单次闪光引起的峰值放电率来测量抑制和促进。MT中方向选择性的主要机制是对零方向运动的放电的明显抑制，我们将其解释为抑制。抑制是足够有力的，以废除单闪光刺激时，他们被嵌入在一系列的闪光在零方向的反应，它经常减少神经元放电的水平低于自发放电率。在首选方向的促进是一个突出的特点，一些，但不是所有的MT神经元的反应。在我们的样本中，大约50%的神经元在优选方向上的频闪运动的峰值放电率是单次闪光的峰值放电率的两倍以上。大多数MT神经元的方向选择性表现出抑制和易化机制的影响，并且不可能根据这些措施将MT神经元分离成不同的组。抑制机制有助于速度调谐以及方向调谐。在82%的测试神经元中，运动在首选方向上的低速截止是由于抑制。高速截止是由于32%的测试神经元受到抑制。后一种机制似乎与抑制机制不同，后者在零方向上起作用，因为其激活需要大的空间间隔。
Mechanisms of direction selectivity and speed selectivity were studied in single neurons of the middle temporal visual area (MT) of behaving macaque monkeys. Visual stimuli were presented in both smooth and stroboscopic motion within a neuron's receptive field as the monkey fixated a stationary point of light. Direction selectivity, speed selectivity, and the spontaneous discharge characteristics of MT neurons in behaving monkeys were similar to those reported in previous studies in anesthetized monkeys. Stroboscopic motion stimuli were sequences of flashes characterized by the spatial and temporal intervals between each flash. The spatial and temporal intervals were systematically varied so that suppressive and facilitatory interactions could be studied in both the preferred and null directions. Suppression and facilitation were measured by subtracting the peak discharge rate elicited by a single flash from the peak discharge rate elicited by a stroboscopic train of flashes. The dominant mechanism of direction selectivity in MT was a pronounced suppression of discharge for motion in the null direction which we interpreted as inhibition. The inhibition was sufficiently potent to abolish the responses to single flashed stimuli when they were embedded in a series of flashes in the null direction, and it frequently reduced the neuronal discharge to a level below the spontaneous firing rate. Facilitation in the preferred direction was a prominent feature of the responses of some, but not all, MT neurons. The peak discharge rate for stroboscopic motion in the preferred direction was more than twice the peak rate to a single flash for approximately 50% of the neurons in our sample. The direction selectivity of most MT neurons showed the effects of both inhibitory and facilitatory mechanisms, and it was not possible to segregate MT neurons into distinct groups on the basis of these measures. Suppressive mechanisms contributed to speed tuning as well as direction tuning. The low-speed cutoff for motion in the preferred direction resulted from suppression in 82% of the neurons tested. The high-speed cutoff resulted from suppression in 32% of the neurons tested. The latter mechanism appeared to be distinct from the inhibitory mechanism which acted in the null direction in that large spatial intervals were required for its activation.