Pasternak T, Albano J E, Harvitt D M
Department of Neurobiology and Anatomy, University of Rochester, New York 14627.
J Neurosci. 1990 Sep;10(9):3079-86. doi: 10.1523/JNEUROSCI.10-09-03079.1990.
Dynamic random dot targets consisting of many localized motion vectors have been used to study the pooling of local motion signals into a global motion percept (Williams and Sekuler, 1984). In such displays, the dots are displaced with a constant step size and the direction of motion for each dot is chosen at random from a specified distribution. When the distribution extends over 360 deg, the display consists only of local random motion of individual dots and no coherent motion is reported. However, when the distribution is less than 360 deg (biased), the stimulus appears to flow in a single direction. We examined the effects of reducing the number of directionally selective (DS) cortical neurons on this integration process. Normal cats and cats with severely reduced proportions of DS neurons were trained on 2 direction discrimination tasks. The discrimination of opposite directions was examined while varying either the range of directions of local motion, or the proportion of dots moving with biased distribution. When all dots in the display were directionally biased, cats with reduced numbers of DS neurons performed the task as well as normal cats and humans (threshold range: 280-320 deg). However, when the proportion of biased dots decreased, these animals had severe deficits. Thus, in the absence of noise, even a very small number of DS neurons can perform spatial pooling of local directional signals, and support normal discrimination of opposite directions. However, a full complement of directional detectors appears necessary when the motion signal is masked by noise. The discrimination of small differences in direction revealed far more severe deficits, even when all the dots in the display were directionally biased (no noise).(ABSTRACT TRUNCATED AT 250 WORDS)
由许多局部运动矢量组成的动态随机点目标已被用于研究局部运动信号汇聚成全局运动感知的过程（Williams和Sekuler，1984）。在这样的显示中，点以恒定步长位移，每个点的运动方向从指定分布中随机选择。当分布覆盖360度时，显示仅由单个点的局部随机运动组成，并且没有报告连贯运动。然而，当分布小于360度（有偏差）时，刺激似乎沿单个方向流动。我们研究了减少方向选择性（DS）皮质神经元数量对这种整合过程的影响。正常猫和DS神经元比例严重降低的猫接受了两项方向辨别任务的训练。在改变局部运动方向范围或有偏差分布的移动点比例的同时，检查对相反方向的辨别。当显示中的所有点都有方向偏差时，DS神经元数量减少的猫与正常猫和人类一样完成任务（阈值范围：280 - 320度）。然而，当有偏差点的比例降低时，这些动物有严重缺陷。因此，在没有噪声的情况下，即使非常少量的DS神经元也可以执行局部方向信号的空间汇聚，并支持对相反方向的正常辨别。然而，当运动信号被噪声掩盖时，似乎需要完整的方向探测器补充。即使显示中的所有点都有方向偏差（无噪声），对方向微小差异的辨别也显示出严重得多的缺陷。（摘要截断于250字）
