Department of Cell and Systems Biology.
Department of Psychology.
eNeuro. 2018 Jan 10;5(6). doi: 10.1523/ENEURO.0407-18.2018. eCollection 2018 Nov-Dec.
The ability to capture the most relevant information from everyday experiences without constantly learning unimportant details is vital to survival and mental health. While decreased activity of the medial prefrontal cortex (mPFC) is associated with failed or inflexible encoding of relevant events in the hippocampus, mechanisms used by the mPFC to discern behavioral relevance of events are not clear. To address this question, we chemogenetically activated excitatory neurons in the mPFC of male rats and examined its impact on local network activity and differential associative learning dependent on the hippocampus. Rats were exposed to two neutral stimuli in two environments whose contingency with an aversive stimulus changed systematically across days. Over 2 weeks of differential and reversal learning, theta band activity began to ramp up toward the expected onset of the aversive stimulus, and this ramping activity tracked the subsequent shift of the set (stimulus modality to environment) predictive of the aversive stimulus. With chemogenetic mPFC activation, the ramping activity emerged within a few sessions of differential learning, which paralleled faster learning and stronger correlations between the ramping activity and conditioned responses. Chemogenetic mPFC activity, however, did not affect the adjustment of ramping activity or behavior during reversal learning or set-shifting, suggesting that the faster learning was not because of a general enhancement of attention, sensory, or motor processing. Thus, the dynamics of the mPFC network activation during events provide a relevance-signaling mechanism through which the mPFC exerts executive control over the encoding of those events in the hippocampus.
从日常经历中捕捉最相关信息的能力对于生存和心理健康至关重要，而不会不断学习不重要的细节。虽然内侧前额叶皮层（mPFC）的活动减少与海马体中相关事件的编码失败或不灵活有关，但 mPFC 用于辨别事件行为相关性的机制尚不清楚。为了解决这个问题，我们化学遗传学地激活了雄性大鼠 mPFC 中的兴奋性神经元，并研究了其对局部网络活动和依赖于海马体的差异联想学习的影响。大鼠在两个环境中暴露于两个中性刺激，其与厌恶刺激的关联在几天内系统地变化。在 2 周的差异和反转学习中，θ波段活动开始向厌恶刺激的预期开始上升，并且这种上升活动跟踪随后的集合（刺激模式到环境）的转变，这预测了厌恶刺激。通过化学遗传学 mPFC 激活，在差异学习的几个会话中出现了上升活动，这与更快的学习和上升活动与条件反应之间更强的相关性相平行。然而，化学遗传学 mPFC 活动并没有影响反转学习或集合转换过程中的上升活动或行为的调整，这表明更快的学习不是因为注意力、感觉或运动处理的一般增强。因此，mPFC 网络在事件期间的动态提供了一种相关性信号机制，通过该机制，mPFC 对海马体中这些事件的编码施加了执行控制。
