Sleep and memory maintain a two-way relationship: the learning and cognitive effort of your day actively shape the structure, depth, and dreams of your following night.

noli's read

The idea that our cognitive activities during the day locally shape the architecture of our night rests on a solid scientific foundation. Research by neuroscientists Giulio Tononi and Chiara Cirelli (experimental EEG studies) broadly supports the concept of 'use-dependent' sleep: brain regions heavily taxed during the day exhibit more intense deep sleep the following night. Studies from Brown University also confirm that sleep spindles activate to consolidate newly learned skills. Nevertheless, the assertion that dream cycles (REM sleep) adjust in a strictly proportional manner to the intensity of learning is slightly exaggerated. Reviews of observational studies show more mixed results regarding the systematic variation of REM sleep duration as a function of cognitive effort. It is primarily the neuronal effort and synaptic fatigue accumulated, rather than 'memories' as abstract entities, that physically dictate this nocturnal reorganization.

the sources

No named source held this one up — that absence is part of the verdict.