A recent study shows that rats, like humans, dream about where they want to go and what they want to do. Scientists showed rats food in a certain location, then coaxed them to sleep before they could get the food. Then, they compared the rats’ brain waves while sleeping to their brain waves when they woke up and were allowed to go get the food—and the patterns of brain activation matched. Further, the rats used their hippocampus, which is a brain region commonly known to be associated with memory and with finding one’s way*. This research contributes new information about the hippocampus; specifically, the hippocampus is associated with imagining the future. One of the study's authors writes:

“What’s surprising here is that we see the hippocampus planning for the future, actually rehearsing totally novel journeys that the animals need to take in order to reach the food.”

Short of being able to ask a rat what they were dreaming about, this is the clearest yet evidence demonstrating that these rodents do indeed dream about tangible, relevant events!

This research demonstrates one purpose of dreams-- rehearsing future action. Another important purpose is to condense and reprocess memory; in fact, a wealth of studies demonstrates the lovely conclusion that getting a good night's sleep is critical for birds learning birdsong. In young birds, plastic changes in the brain occur at nighttime to integrate sensorimotor feedback with sensory memories, while sleep also helps adult birds refine their song.

The moral of the story? If you are considering either pulling an all-nighter to study for an exam or getting some sleep, you are probably better off getting some sleep!

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* A famous study of London taxi cab drivers found enlarged hippocampi, indicating (i) that this region is associated with spatial memory and knowledge, and (ii) the brain is highly plastic, and one's job, habits, and environment very much affect brain deelopment throughout life.