Crick and Mitchison's theory of REM sleep and neural networks

Crick and Mitchison proposed that a reverse learning mechanism in REM sleep removes certain undesirable modes of interaction in neural networks within the cerebral cortex. If their theory is correct then abnormalities of reverse learning might account for some aspects of schizophrenia, mania, and depression. The theory of reverse learning might lead to an understanding of why lithium salts terminate manic episodes.