Neural basis of a perceptual decision in the parietal cortex (area LIP) of the rhesus monkey
Neural basis of a perceptual decision in the parietal cortex (area LIP) of the rhesus monkey
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DOI：
10.1152/jn.2001.86.4.1916
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发表时间：
2001-10-01
影响因子：
2.5
通讯作者：
Newsome, WT
中科院分区：
文献类型：
--
作者：
Shadlen, MN;Newsome, WT
我们记录了两只恒河猴在辨别随机点视觉刺激中运动方向时顶叶后皮层（LIP区）单个神经元的活动。视觉任务是类似的运动歧视的任务，已在以前的调查中使用的运动敏感区域的纹外皮层。这些猴子被训练来决定运动的方向是否朝向随机点刺激两侧的两个选择目标之一。在试验结束时，猴子通过向适当的目标进行眼球运动来报告他们的方向判断。我们研究了LIP中的神经元，这些神经元在延迟扫视眼球运动任务中表现出空间选择性的持续活动。这些神经元被认为携带高水平的信号，适合于识别显著的视觉目标和指导扫视眼球运动。我们安排了运动辨别任务，使得其中一个选择目标位于LIP神经元的反应场（RF）中，而另一个目标位于远离RE的位置。在运动观察期间，LIP中的神经元以预测猴子在试验结束时会进行的扫视眼球运动的方式改变了它们的放电率。因此，这种活动预测了猴子对运动方向的判断。这种预测活动在观察运动的早期就开始了，随着猴子观察随机点的运动，这种预测活动变得越来越可靠。神经活动预测了猴子对简单和困难试验（强和弱运动）的方向判断，无论判断是否正确。此外，反应的时间和幅度受到刺激中运动信号强度的影响。当运动方向朝向RF时，更强的运动导致更大的神经反应在运动观察期的早期。当运动远离RF时，更强的运动导致对正在进行的活动的更大抑制。因此，LIP区单个神经元的活动既反映了即将发生的注视转移的方向，也反映了指示这种反应的感觉信息的质量。神经反应的时间进程表明，LIP积累与眼动目标选择相关的感觉信号。
We recorded the activity of single neurons in the posterior parietal cortex (area LIP) of two rhesus monkeys while they discriminated the direction of motion in random-dot visual stimuli. The visual task was similar to a motion discrimination task that has been used in previous investigations of motion-sensitive regions of the extrastriate cortex. The monkeys were trained to decide whether the direction of motion was toward one of two choice targets that appeared on either side of the random-dot stimulus. At the end of the trial, the monkeys reported their direction judgment by making an eye movement to the appropriate target. We studied neurons in LIP that exhibited spatially selective persistent activity during delayed saccadic eye movement tasks. These neurons are thought to carry high-level signals appropriate for identifying salient visual targets and for guiding saccadic eye movements. We arranged the motion discrimination task so that one of the choice targets was in the LIP neuron's response field (RF) while the other target was positioned well away from the RE During motion viewing, neurons in LIP altered their firing rate in a manner that predicted the saccadic eye movement that the monkey would make at the end of the trial. The activity thus predicted the monkey's judgment of motion direction. This predictive activity began early in the motion-viewing period and became increasingly reliable as the monkey viewed the random-dot motion. The neural activity predicted the monkey's direction judgment on both easy and difficult trials (strong and weak motion), whether or not the judgment was correct. In addition, the timing and magnitude of the response was affected by the strength of the motion signal in the stimulus. When the direction of motion was toward the RF, stronger motion led to larger neural responses earlier in the motion-viewing period. When motion was away from the RF, stronger motion led to greater suppression of ongoing activity. Thus the activity of single neurons in area LIP reflects both the direction of an impending gaze shift and the quality of the sensory information that instructs such a response. The time course of the neural response suggests that LIP accumulates sensory signals relevant to the selection of a target for an eye movement.