Why do we dream and what are the latest scientific theories?

The answer

Modern dream research has converged on several complementary theories. The 'threat simulation theory' proposed by Antti Revonsuo suggests dreams evolved to rehearse dangerous scenarios, supported by the prevalence of threat-related content across cultures. The 'memory consolidation' theory, backed by a 2020 study in Science, showed that hippocampal replay during REM sleep strengthens newly formed memories by 20-40%. Erik Hoel's 2021 'overfitted brain hypothesis' proposes dreams act like data augmentation in machine learning, injecting noise to prevent the brain from overfitting to daily experiences. During REM sleep, the brain consumes as much glucose as when awake, while the body is paralyzed by glycine-mediated motor neuron inhibition - suggesting dreams serve active cognitive functions.