Taken together, the above findings suggest that ripple-related reactivation of CA1 neurons and subsequent spindle-related reactivation of mPFC neurons may facilitate transfer of memories from the hippocampus to the mPFC during slow-wave sleep. The highly synchronous firing of CA1 neurons during sharp wave-ripples probably activates neurons in the main output of CA1, the subiculum. If CA1 firing during sharp wave-ripples activates neurons in the subiculum and mPFC at roughly the same time, then the subiculum and mPFC could in turn simultaneously activate common targets, such as the deep layers of the entorhinal cortex [42], potentially leading to associative long-term potentiation. If so, then mPFC inputs could eventually activate such targets on their own, and this could potentially explain why some initially hippocampal-dependent memories gradually become dependent on the mPFC [43,44].
