Representation of an abstract perceptual decision in macaque superior colliculus
Representation of an abstract perceptual decision in macaque superior colliculus
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DOI：
10.1152/jn.00872.2003
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发表时间：
2004-05-01
影响因子：
2.5
通讯作者：
Newsome, WT
中科院分区：
文献类型：
--
作者：
Horwitz, GD;Batista, AP;Newsome, WT
当猴子执行一项新的方向辨别任务时，我们记录了上丘(SC)的中层和深层神经元。与我们之前使用的任务不同，新版本要求猴子将感知判断与执行特定操作性眼跳的准备分开。猴子在随机点运动刺激中辨别出两个相反的运动方向，并被要求在所需操作员扫视的目标被揭示之前的一段延迟期内保持记忆中的决定。我们假设，在这个范式中做出的知觉决定将在大脑中以一种“抽象”或“绝对”的形式呈现，可能是在额叶皮质，与决策相关的神经活动将从空间组织的前视运动结构(如SC)中消失。然而，令我们惊讶的是，在实验的早期，在猴子计划操作性眼跳之前，SC中层和深层的一小部分神经元以一种特定于选择的方式被激发。此外，延迟期内决策的表征似乎是空间的：SC图中的活动区域对应于感知区分的刺激运动流向的空间区域。电微刺激实验表明，这些与决策相关的SC信号不仅与隐蔽的眼跳规划有关。我们的结论是，猴子可能部分地使用空间参照的助记策略来表示知觉决定，即使抽象的、直截了当的表示可能更像是先验的。
We recorded from neurons in the intermediate and deep layers of the superior colliculus (SC) while monkeys performed a novel direction discrimination task. In contrast to the task we used previously, the new version required the monkey to dissociate perceptual judgments from preparation to execute specific operant saccades. The monkey discriminated between 2 opposed directions of motion in a random-dot motion stimulus and was required to maintain the decision in memory throughout a delay period before the target of the required operant saccade was revealed. We hypothesized that perceptual decisions made in this paradigm would be represented in an "abstract" or "categorical" form within the brain, probably in the frontal cortex, and that decision-related neural activity would be eliminated from spatially organized preoculomotor structures such as the SC. To our surprise, however, a small population of neurons in the intermediate and deep layers of the SC fired in a choice-specific manner early in the trial well before the monkey could plan the operant saccade. Furthermore, the representation of the decision during the delay period appeared to be spatial: the active region in the SC map corresponded to the region of space toward which the perceptually discriminated stimulus motion flowed. Electrical microstimulation experiments suggested that these decision-related SC signals were not merely related to covert saccade planning. We conclude that monkeys may employ, in part, a spatially referenced mnemonic strategy for representing perceptual decisions, even when an abstract, categorical representation might appear more likely a priori.