The representation of odor in olfactory cortex (piriform) is distributive and unstructured and can only be afforded behavioral significance upon learning. We performed 2-photon imaging to examine the representation of odors in piriform and in two downstream areas, the orbitofrontal cortex (OFC) and the medial prefrontal cortex (mPFC), as mice learned olfactory associations. In piriform, we observed that odor responses were largely unchanged during learning. In OFC, 30% of the neurons acquired robust responses to conditioned stimuli (CS+) after learning, and these responses were gated by internal state and task context. Moreover, direct projections from piriform to OFC can be entrained to elicit learned olfactory behavior. CS+ responses in OFC diminished with continued training, whereas persistent representations of both CS+ and CS− odors emerged in mPFC. Optogenetic silencing indicates that these two brain structures function sequentially to consolidate the learning of appetitive associations.

嗅觉皮层（梨状状）中气味的表示是分布性的，无组织的，仅在学习时才具有行为上的意义。我们进行了2光子成像，以检查梨形糖和两个下游区域（眶额叶皮层（OFC）和内侧前额叶皮层（mPFC））中气味的表现，因为小鼠学会了嗅觉关联。在梨状菌中，我们观察到在学习过程中气味反应基本保持不变。在OFC中，学习后，有30％的神经元获得了对条件刺激（CS +）的强烈响应，而这些响应是由内部状态和任务环境决定的。此外，可以携带从梨状细胞到OFC的直接投影来引发学习的嗅觉行为。持续训练会降低OFC中CS +的反应，而在mPFC中出现了CS +和CS-气味的持久性表示。光遗传学沉默表明这两个大脑结构顺序发挥功能，以巩固对食欲联想的学习。