The Defensive Activation theory: dreaming as a mechanism to prevent takeover of the visual cortex

Abstract

Regions of the brain maintain their territory with continuous activity: if activity slows or stops (e.g., because of blindness), the territory tends to be taken over by its neighbors. A surprise in recent years has been the speed of takeover, which is measurable within an hour. These findings lead us to a new hypothesis on the origin of dream sleep. We hypothesize that the circuitry underlying dreaming serves to amplify the visual system’s activity periodically throughout the night, allowing it to defend its territory against takeover from other senses. We find that measures of plasticity across 25 species of primates correlate positively with the proportion of rapid eye movement (REM) sleep. We further find that plasticity and REM sleep increase in lockstep with evolutionary recency to humans. Finally, our hypothesis is consistent with the decrease in REM sleep and parallel decrease in neuroplasticity with aging.

The overfitted brain: Dreams evolved to assist generalization

“…Examples of this include the hypothesis that dreams are a test-bed for strengthening the brain's ability to generate mental imagery during wake, explaining the complexification of dreams from childhood to adulthood. 120 Another example of a novel hypothesis that does not stand in opposition to the OBH is that dreams are for defending neural real estate 163 (although this may be contradicted by non-wake activation profiles during dreaming). As a hypothesis, it shares similar background concerns with that of the free energy approach to ll OPEN ACCESS dreaming, 116 although without assuming that dreams are for testing the predictions of a generative self-model's priors or that dreams should become less surprising over time as inputless prediction error is minimized.…”