Study of the neural representation of different aspects of color perception in the inferior temporal cortex and the prefrontal cortex of the monkey

辨别和分类是我们色觉的两个不同方面。一方面，我们可以辨别颜色的细微差别；另一方面，我们把相似的颜色归为一组，比如“红色”。为了研究这些不同的色觉方面对下颞叶皮层颜色编码的影响，我们记录了两只日本猴子在颜色分类任务和颜色辨别任务训练时的TE区神经元反应。在这两个任务中，当猴子盯着注视点时，在中央凹上呈现一个测试刺激。在颜色分类任务中，注视点和扫视点是在测试刺激出现后出现的。研究人员训练猴子在看到红色时保持注视，在看到绿色时进行扫视。在辨色任务中，在呈现一种测试颜色后，同时显示两种颜色刺激（辨色刺激）。猴子们被训练朝着与测试相同的颜色扫视。在这两个任务中，我们使用了11种测试颜色，它们以从红色到绿色的相同间隔排列。猴子也接受了简单的视觉固定任务训练。从TE区域的一个子区域记录神经元，其中神经元具有很强的颜色选择性，但很少有形状选择性。从该区域记录的颜色选择神经元在不同的任务中表现出非常相似的颜色调节，包括分类、辨别和简单的固定。这些结果表明，TE神经元编码准确的颜色信息独立于任务需求。

Discrimination and categorization are two different aspects of our color vision. On the one hand, we can discriminate subtle difference in color; on the other hand, we categorize similar colors into a single group such as 'red'. To study the effects of these different aspects of color vision on the color coding in the inferior temporal cortex, we recorded neuronal responses in area TE of two Japanese monkeys trained a color categorization task and a color discrimination task. In both tasks, while the monkey was gazing at the fixation spot, a test stimulus was presented on the fovea. In color categorization task, fixation point and saccade point were shown after presentation of a test stimulus. Monkeys were trained to keep fixation when reddish color was presented and to make saccade, when greenish color was presented as test. In color discrimination task, two color stimuli (discrimination stimuli) were shown simultaneously after presentation of a test color. Monkeys were trained to make saccade toward the same color as the test. In both tasks, we used eleven test colors that were arranged at equal intervals from red to green. Monkeys were also trained a simple visual fixation task. Neurons were recorded from a sub-region in area TE where neurons have strong color selectivity, but little shape selectivity. Color selective neurons recorded from this region showed color tuning which was very similar across different tasks including categorization, discrimination and simple fixation. These results suggest that TE neurons code exact color information independent of the task demand.