Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
J Neurosci. 2010 Feb 17;30(7):2464-71. doi: 10.1523/JNEUROSCI.5781-09.2010.
The discovery that dopamine neurons signal errors in reward prediction has demonstrated that concepts empirically derived from the study of animal behavior can be used to understand the neural implementation of reward learning. Yet the learning theory models linked to phasic dopamine activity treat attention to events such as cues and rewards as static quantities; other models, such as Pearce-Hall, propose that learning might be influenced by variations in processing of these events. A key feature of these accounts is that event processing is modulated by unsigned rather than signed reward prediction errors. Here we tested whether neural activity in rat basolateral amygdala conforms to this pattern by recording single units in a behavioral task in which rewards were unexpectedly delivered or omitted. We report that neural activity at the time of reward is providing an unsigned error signal with characteristics consistent with those postulated by these models. This neural signal increased immediately after a change in reward, and stronger firing was evident whether the value of the reward increased or decreased. Further, as predicted by these models, the change in firing developed over several trials as expectations for reward were repeatedly violated. This neural signal was correlated with faster orienting to predictive cues after changes in reward, and abolition of the signal by inactivation of basolateral amygdala disrupted this change in orienting and retarded learning in response to changes in reward. These results suggest that basolateral amygdala serves a critical function in attention for learning.
多巴胺神经元信号错误预测奖励的发现表明，从动物行为研究中得出的经验概念可以用来理解奖励学习的神经实现。然而，与相位多巴胺活动相关的学习理论模型将对事件（如线索和奖励）的关注视为静态量；其他模型，如 Pearce-Hall 模型，提出学习可能会受到这些事件处理变化的影响。这些解释的一个关键特征是，事件处理是由无符号而不是有符号的奖励预测误差来调节的。在这里，我们通过在一项行为任务中记录单个单元来测试大鼠基底外侧杏仁核的神经活动是否符合这一模式，在该任务中，奖励会意外地给予或省略。我们报告说，奖励时的神经活动提供了一个无符号的错误信号，其特征与这些模型所假设的特征一致。这个神经信号在奖励发生变化后立即增加，并且无论奖励的价值增加还是减少，都可以明显看出更强的发射。此外，正如这些模型所预测的那样，由于奖励的预期反复被违反，随着时间的推移，发射的变化在几个试验中逐渐发展。这个神经信号与奖励变化后对预测线索更快的定向有关，而基底外侧杏仁核的失活消除了这个信号，扰乱了这种对奖励变化的定向变化，并阻碍了对奖励变化的学习。这些结果表明，基底外侧杏仁核在学习注意力方面起着关键作用。
