I've recently became aware of the idea of "reverse learning" that might happen during REM sleep - the brain's attempt to eliminate pathological attractors that might appear in neural networks. The idea was originally expressed by Crick and Mitchison in their 1983 paper on "The function of dream sleep".

I'm interested if there has any recent work that has supported that idea. I'm aware of this wikipedia article on reverse learning. More specifically, I'm interested in how dream recall (writing down or recalling dreams upon awakening) affects the process of "reverse learning"?


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Recent supporting work

In a paper published in the Jan 2017 issue of Nature Neuroscience, Wei Li and colleagues propose a mechanism that supports the "reverse learning" process based on dendritic calcium spikes that regulate spine formation.

However, as the authors discuss, the implications of their findings are more nuanced. They support the idea of reverse learning but show that it is not the only thing going on in REM sleep:

REM sleep is not simply a substitute for wakefulness to stimulate plasticity, for pruning synapses during development or for persevering genetic identities of neuronal circuits. Instead, REM sleep is important for selectively incorporating new synapses into the existing circuits. It could be viewed as a “selection committee” for building and maintaining the synaptic network.

Dream recall

If we accept that reverse learning functions by the proposed mechanism, I would guess it would not be perturbed significantly by dream recall. This is because the calcium spikes in their experiments occurred on the order of seconds, and only during REM sleep. Dream recall, on the other hand, is is a high-level mental process that is probably restricted to humans.

This is just my best intuitive guess. For all we know, any neural event anywhere in the brain can potentially influence a subsequent event anywhere else in the brain, so really all bets are still on the table.


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