Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel 76100.
J Neurosci. 2012 Jun 20;32(25):8598-610. doi: 10.1523/JNEUROSCI.0323-12.2012.
Extensive evidence implicates the amygdala as a major station for acquisition, extinction, and consolidation of emotional memories. Most of this work relies on fear-conditioning in rodents and imaging in humans. Few studies have explored coding of value in the primate amygdala, but the circuitry that underlies extinction and overnight retention remains largely unexplored. We developed a learning paradigm for nonhuman primates (macaca fascicularis) and recorded the activity of single neurons during the different stages of acquisition, extinction, and overnight consolidation of pleasant and aversive tone-odor associations. We find that many neurons become phase-locked to respiratory cycles in a stage-dependent manner, emphasizing the flexibility of amygdala neurons to represent the current state and change their spontaneous activity accordingly. We suggest that these changes can serve to increase neuronal sensitivity to an upcoming event and facilitate learning mechanisms. We further show formation of aversive-bias during the acquisition of associations and during overnight retention, in the sense that neurons preferentially code for the aversive conditioned stimuli, even if they initially homogenously represent value of the reinforcer. Our findings show flexible representations in the primate amygdala during the different cycles of learning and memory, and suggest selective potentiation of aversive information.
大量证据表明杏仁核是情绪记忆获得、消退和巩固的主要部位。这些工作大多依赖于啮齿动物的恐惧条件反射和人类的成像研究。很少有研究探索灵长类动物杏仁核中的价值编码，但仍有很大一部分关于消退和隔夜保留的神经回路尚未得到探索。我们为非人类灵长类动物（猕猴）开发了一种学习范式，并在获得、消退和隔夜巩固愉快和厌恶的音调-气味关联的不同阶段记录单个神经元的活动。我们发现，许多神经元以依赖于阶段的方式与呼吸周期同步锁定，强调了杏仁核神经元的灵活性，以代表当前状态并相应地改变其自发活动。我们认为这些变化可以提高神经元对即将发生的事件的敏感性，并促进学习机制。我们进一步表明，在关联的获得和隔夜保留期间形成了厌恶偏见，因为神经元优先编码厌恶条件刺激，即使它们最初均匀地代表强化物的价值。我们的研究结果表明，在不同的学习和记忆周期中，灵长类动物的杏仁核具有灵活的表现形式，并表明对厌恶信息的选择性增强。
