Sleep and Memory

The link between good sleep and a sound mind may have to do with the way that dreams deal with memories. One might think that the engagement of the imagination with memory that occurs in dreams is a better way of processing hard memories than the wakeful obsessing over them; but the scientists say maybe the real benefit is just that the parts of your brain that suppress memories are better-rested.

Eighty-five healthy adults attempted to suppress unwanted memories while images of their brain were taken using functional MRI. Half of the participants enjoyed a restful night of sleep in the sleep lab before the task, whereas the other half stayed awake all night.

During memory suppression, the well-rested participants showed more activation in the right dorsolateral prefrontal cortex -- a brain region that controls thoughts, actions, and emotions -- compared to those who stayed awake all night. The rested participants also showed reduced activity in the hippocampus -- a brain region involved in memory retrieval -- during attempts to suppress unwanted memories.

Among the participants who slept in the lab, those who spent more time in REM sleep were better able to engage the right dorsolateral prefrontal cortex during memory suppression, pointing to a role for REM sleep in restoring prefrontal control mechanisms underpinning the ability to prevent unwanted memories from entering conscious thought.

It strikes me that REM sleep is supposed to be when dreams occur, so maybe the more natural hypothesis is (also?) correct. Dreaming may help process the memories so they aren't so upsetting; rest may help the brain deal with the need to wakefully suppress old thoughts.