Rats Dream About Their Future, Like Humans

Do rats dream? They apparently do. When rats rest, their brains simulate journeys to a desired future, such as a tasty treat, according to new research.

In this latest study, scientists monitored the brain activity in rats. They first examined it as the animals viewed food in a location they could not reached; then, they monitored brain activity as the rats rested in a separate chamber and finally they monitored activity as the rats were allowed to walk to the food.

"During exploration, mammals rapidly form a map of the environment in their hippocampus," said Hugo Spiers, one of the researchers, in a news release. "During sleep or rest, the hippocampus replays journeys through this map which may help strengthen the memory. It has been speculated that such replay might form the content of dreams. Whether or not rats experience this brain activity as dreams sis still unclear, as we would need to ask them to be sure! Our new results show that during rest the hippocampus also constructs fragments of a future yet to happen. Because the rat and human hippocampus are similar, this may explain why patients with damage to their hippocampus struggle to imagine future events."

In fact, the results suggest that the hippocampus plans routes that have not yet happened. It's likely that this section of the brain also record events that have already happened, but only when there is a motivational cue, such as food. This may also imply that the ability to imagine future events is not a uniquely human ability.

"What we don't know at the moment is what these neural simulations are actually for," said Caswell Barry, co-lead author of the new study. "It seems possible this process is a way of evaluating the available options to determine which is the most likely to end in reward, thinking it through if you like. We don't know that for sure though and something we'd like to do in the future is try to establish a link between this apparent planning and what the animals do next."

The findings are published in the journal eLife.

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