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Rats plan journeys to the reward in their dreams

Posted June 29, 2015

Dreams have always puzzled people. Some tried to explain them and to predict future according to them, others always wanted to understand mechanisms involved in dreaming. Now scientists at University College London have conducted a research and found out that rats dream about journeys to a desired future such as a tasty treats. However, this was achieved not just to satisfy curiosity of scientists – it actually has an important value for health sciences.

The research showed that rats dream about path to the food in their sleep. Such results were achieved through monitoring of brain activity and could explain some human conditions as well. Image credit: John Ruby via Wikimedia, CC0 1.0 Public Domain

The research showed that rats dream about path to the food in their sleep. Such results were achieved through monitoring of brain activity and could explain some human conditions as well. Image credit: John Ruby via Wikimedia, CC0 1.0 Public Domain

Of course, researching dreams is not easy and requires creative solutions. During the research, scientists monitored brain activity in rats several times. The first time they monitored brain activity of the rats when they were looking at food that was placed in a location impossible for them to reach. Second time was when they were sleeping in a separate chamber. Third – as rats were allowed to walk to the food. Scientists noticed activity of specialised brain cells involved in navigation, which suggests that during the rest the rats simulated walking to and from food that they had been unable to reach.

During the experiment, rats were put on a straight track with a T-junction ahead. At one side of this junction there was food, while the other side was empty. This junction was blocked with a transparent barrier. Rats were allowed to observe the situation and then were sleeping in a different chamber. After the sleep the barrier was removed, the animals were returned to the track and could run to the junction and to the food.

As well as providing better understanding about animal behaviour and answering some questions about dreams, these results can be useful in other ways as well. Results of the research could help to explain why some people with a damages part of the brain called the hippocampus are unable to imagine the future.

Senior author Dr Hugo Spiers said that during the exploration of the environment rats form a map of the place in their hippocampus. He noted that “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 is still unclear, as we would need to ask them to be sure!”

However, even though rats are not very talkative about their dreams, results of the research suggest that hippocampus also constructs fragments of a future yet to happen. That is why scientists think that it could explain why people with damaged hippocampus cannot imagine future events. During the sleep researchers found that place cells that would later provide an internal map of the food arm were active. Brain cells that represented the empty arm with no food were not active in this way, which shows that rats were simulating future paths leading to a desired goal.

Before this research, scientists new that hippocampus is important for memory, storing details about locations person has visited. However, now scientists found out that hippocampus is also important in planning of the future. It participates in dreams that rehearse novel journeys. This means that hippocampus may do both – record previous journeys as well as plan future ones. Scientists say that for rats food has to be involved as extra motivation, but results show that the ability to imagine future events is not a uniquely human ability.

However, there is still a lot of things to research. Scientists note that they still do not know what these neural simulations are actually for. It may be a way to evaluate the options to choose the best way to achieve the reward. That is why the next stage of the research should be establishing a link between this planning and animal behaviour after the dreaming of the future. It looks like dreams are still puzzling scientists and will continue to tease the imagination and curiosity of many.

Source: UCL

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