Range-adapting representation of economic value in the orbitofrontal cortex.
Range-adapting representation of economic value in the orbitofrontal cortex.
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DOI：
10.1523/jneurosci.3751-09.2009
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发表时间：
2009-11-04
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通讯作者：
Padoa-Schioppa C
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作者：
Padoa-Schioppa C
在做出经济选择时，个人会将主观价值赋予可用选项。然而，在不同的行为条件下计算的值可能会有很大的差异。同一个人有时可能会在价值几美元的商品之间做出选择，而有时可能会在价值数千美元或更多的商品之间做出选择。计算价值的大脑系统--“估值系统”--如何处理这种巨大的变异性？在这里，我们表明，眼眶额叶皮质(OFC)的价值表征-经济选择过程中的价值分配涉及的一个区域-适应于选择的行为条件，更具体地说，是适应在任何给定条件下可用的价值范围。在实验中，猴子在不同的果汁之间进行选择，它们的选择模式提供了一种主观价值的衡量标准。值范围因会话而异，在每个会话中，OFC神经元以线性方式编码值。在整个人群中，神经元敏感度(定义为由一个值单位的增加引起的神经元活动的变化)与值范围成反比。相反，神经元的活动范围并不依赖于数值范围。这种范围适应现象与先前研究中观察到的菜单不变现象相辅相成。事实上，每个神经元的活动适应它编码的范围值，但不依赖于其他可用的商品。因此，我们的结果表明，OFC中的值表示同时具有偏好传递性(菜单不变性)和计算效率(范围适应)的实例性。
While making economic choices, individuals assign subjective values to the available options. Values computed in different behavioral conditions, however, can vary substantially. The same person might choose some times between goods worth a few dollars, and other times between goods worth thousands of dollars, or more. How does the brain system that computes values—the “valuation system”—handle this large variability? Here we show that the representation of value in the orbitofrontal cortex (OFC)—an area implicated in value assignment during economic choice—adapts to the behavioral condition of choice and, more specifically, to the range of values available in any given condition. In the experiments, monkeys chose between different juices and their choice patterns provided a measure of subjective value. Value ranges were varied from session to session and, in each session, OFC neurons encoded values in a linear way. Across the population, the neuronal sensitivity (defined as the change in neuronal activity elicited by the increase in one value unit) was inversely proportional to the value range. Conversely, the neuronal activity range did not depend on the value range. This phenomenon of range adaptation complements that of menu invariance observed in a previous study. Indeed, the activity of each neuron adapts to the range values it encodes, but does not depend on other available goods. Our results thus suggest that the representation of value in the OFC is at one time instantiative of preference transitivity (menu invariance) and computationally efficient (range adaptation).