Findlay Graham, Tononi Giulio, Cirelli Chiara
Department of Psychiatry, University of Wisconsin-Madison, Madison, WI, USA.
Neuroscience Training Program, University of Wisconsin-Madison, Madison, WI, USA.
Sleep Adv. 2021 Jan 30;1(1):zpab002. doi: 10.1093/sleepadvances/zpab002. eCollection 2020.
The term hippocampal replay originally referred to the temporally compressed reinstantiation, during rest, of sequential neural activity observed during prior active wake. Since its description in the 1990s, hippocampal replay has often been viewed as the key mechanism by which a memory trace is repeatedly rehearsed at high speeds during sleep and gradually transferred to neocortical circuits. However, the methods used to measure the occurrence of replay remain debated, and it is now clear that the underlying neural events are considerably more complicated than the traditional narratives had suggested. "Replay-like" activity happens during wake, can play out in reverse order, may represent trajectories never taken by the animal, and may have additional functions beyond memory consolidation, from learning values and solving the problem of credit assignment to decision-making and planning. Still, we know little about the role of replay in cognition, and to what extent it differs between wake and sleep. This may soon change, however, because decades-long efforts to explain replay in terms of reinforcement learning (RL) have started to yield testable predictions and possible explanations for a diverse set of observations. Here, we (1) survey the diverse features of replay, focusing especially on the latest findings; (2) discuss recent attempts at unifying disparate experimental results and putatively different cognitive functions under the banner of RL; (3) discuss methodological issues and theoretical biases that impede progress or may warrant a partial revaluation of the current literature, and finally; (4) highlight areas of considerable uncertainty and promising avenues of inquiry.
“海马体重演”这一术语最初指的是在休息期间，之前清醒活动时观察到的序列神经活动在时间上被压缩后的重新实例化。自20世纪90年代被描述以来，海马体重演常常被视为一种关键机制，通过该机制，记忆痕迹在睡眠期间以高速反复排练，并逐渐转移到新皮质回路。然而，用于测量重演发生的方法仍存在争议，现在很明显，潜在的神经事件比传统描述所暗示的要复杂得多。“类似重演”的活动在清醒时也会发生，可以以相反的顺序进行，可能代表动物从未走过的轨迹，并且可能具有除记忆巩固之外的其他功能，从学习价值、解决信用分配问题到决策和规划。尽管如此，我们对重演在认知中的作用以及它在清醒和睡眠状态下的差异程度知之甚少。然而，这种情况可能很快就会改变，因为数十年来用强化学习（RL）来解释重演的努力已经开始产生可测试的预测以及对一系列不同观察结果的可能解释。在这里，我们（1）综述重演的各种特征，特别关注最新发现；（2）讨论最近试图将不同的实验结果和假定不同的认知功能统一在强化学习的框架下；（3）讨论阻碍进展或可能需要对当前文献进行部分重新评估的方法问题和理论偏差，最后；（4）强调存在大量不确定性的领域以及有前景的研究途径。
