Paton Joseph J, Belova Marina A, Morrison Sara E, Salzman C Daniel
Center for Neurobiology and Behavior, Columbia University, 1051 Riverside Drive, Unit 87, New York, New York 10032, USA.
Nature. 2006 Feb 16;439(7078):865-70. doi: 10.1038/nature04490.
Visual stimuli can acquire positive or negative value through their association with rewards and punishments, a process called reinforcement learning. Although we now know a great deal about how the brain analyses visual information, we know little about how visual representations become linked with values. To study this process, we turned to the amygdala, a brain structure implicated in reinforcement learning. We recorded the activity of individual amygdala neurons in monkeys while abstract images acquired either positive or negative value through conditioning. After monkeys had learned the initial associations, we reversed image value assignments. We examined neural responses in relation to these reversals in order to estimate the relative contribution to neural activity of the sensory properties of images and their conditioned values. Here we show that changes in the values of images modulate neural activity, and that this modulation occurs rapidly enough to account for, and correlates with, monkeys' learning. Furthermore, distinct populations of neurons encode the positive and negative values of visual stimuli. Behavioural and physiological responses to visual stimuli may therefore be based in part on the plastic representation of value provided by the amygdala.
视觉刺激可以通过与奖励和惩罚的关联获得正价值或负价值，这一过程称为强化学习。尽管我们现在对大脑如何分析视觉信息已经了解很多，但对于视觉表征如何与价值建立联系却知之甚少。为了研究这一过程，我们将目光转向杏仁核，这是一种与强化学习有关的脑结构。我们记录了猴子个体杏仁核神经元的活动，在此期间抽象图像通过条件作用获得了正价值或负价值。在猴子学会最初的关联后，我们颠倒了图像的价值分配。我们检查了与这些颠倒相关的神经反应，以便估计图像的感官属性及其条件价值对神经活动的相对贡献。我们在此表明，图像价值的变化会调节神经活动，而且这种调节发生得足够快，足以解释猴子的学习行为并与之相关。此外，不同的神经元群体编码视觉刺激的正价值和负价值。因此，对视觉刺激的行为和生理反应可能部分基于杏仁核提供的价值的可塑性表征。
