What Are Dreams?

Answer by Paul King, Computational Neuroscientist

Are dreams a doorway into another realm? Our subconscious mind trying to send us messages? Or an artifact of nighttime brain activity?

Recent developments in neuroscience shed light onto why we dream and where the content of dreams comes from.

Neurological Basis of Dreaming

Dreaming can be thought of as a protoconscious state [1] which occurs mostly during Rapid Eye Movement (REM) sleep, but also during other sleep stages such as stage 4 Slow Wave Sleep (SWS), the deepest sleep stage. Studies have shown that the nature of dreams varies according to the sleep stage in which they occur, with most dreams reported during REM sleep.

[As viewed in this figure], sleep stages occur in cycles (called “bouts”) over the course of the night. Dreaming occurs during REM but also during certain deeper stages.

The emerging view in neuroscience is that dreams are related to memory consolidation happening in the brain during sleep. This may include reorganizing and recoding memories in relation to emotional drives as well as transferring memories between brain regions.

During the day, episodic memories (memories for events) are stored in the hippocampus, a region of the brain specialized for long-term memory that learns particularly quickly. At night, memories from this region appear to be transferred to the cerebral cortex, the region specialized for information processing, cognition, and knowledge. [2] [3]

Studies in animals have found that during sleep, the neural activity of the hippocampus “replays” the events of the day. This replay happens faster than real-time, and sometimes happens in reverse. The activity replay is correlated with neural activity patterns in both the visual cortex (responsible for visual experience) and the prefrontal cortex (responsible for strategy, goals, and planning). The memory replay occurs during REM sleep and dreaming. [4]

Dreams and the Subconscious

But what —> Read More