During sleep, memories about our previous experience are replayed, as was previously shown in the hippocampus, in the neocortex and in the striatum. This replay is probably important for memory consolidation, the process of stabilization of memories that is thought to be orchestrated by the hippocampus. With Adrien Peyrache, Karim Benchenane, Mehdi Khamassi, and Sidney Wiener at the CNRS, Laboratoire de Physiology de la Perception et de l’Action, Collège de France, Paris, we have shown that replay in the prefrontal cortex is correlated with hippocampal sharp waves. Because sharp waves are when most of the hippocampal replay takes place, this supports the view that information processing in the cortex during sleep is under hippocampal control.  Moreover, in this work, which is the centerpiece of Adrien’s PhD dissertation, we show that not everything about experience is equally replayed. As the figure above shows (please go to the original paper on Nature Neuroscience, just published this week, for details) activity patterns from the “choice points” in the task, and after the rat has learned the task, are the most likely to be replayed. 

Thus, there seems to be a mechanisms determining what the most relevant information is, and what deserves to be replayed, and maybe consolidated. We will get back to you soon – hopefully – with some ideas about what this mechanism may be. 

For the moment, my thanks to Adrien and the other authors!