How our brains make educated guesses

British scientists say they have identified how cells in the brain work together to combine memories of separate experiences, allowing us to make educated guesses in everyday life.

Cells also can link different memories while we are resting or sleeping, a process that may be important in creativity, they write in a paper in the journal Cell.

Helen Barron and David Dupret from the University of Oxford began by isolating this ability to the hippocampus, an area of the brain known to play a role in learning and memory. They then ran a set of similar experiments with people and mice.

Human volunteers were asked to play a virtual reality game where hearing a sound, such as running water, signalled that they would also see a colourful picture appear on the wall. They would then play a second game where finding the colourful pictures would help them win money.

The sound was never directly connected to winning money, yet the volunteers began to guess that the sound was linked to the prize and when they heard it, they would look for the reward.

The experiment was recreated in mice by playing a sound before showing a picture made from LED lights. Then, in a separate stage of the task, the mice could find a reward of sugar water if the lights were turned on. Like the people, the mice began connecting the sound with the reward.

“By carrying out similar experiments with both mice and people, this work shows that the process of establishing a link between separate events is common to both species,” Dupret says. “And by working with mice, it’s then possible to examine what’s going on in the brain of a mammal at the level of individual cells.”

In mouse brains, the researchers could record the activity of brain cells that individually represented sounds, lights or rewards. As the mice began to infer that a sound was logically linked to the reward via a light, they found that the cells began to fire in that order.

They kept monitoring the mice when they rested after completing the task and saw that their brains began jumping over the intermediate “light” step. The “sound” brain cells became active with the “reward” brain cells; joining the dots between different experiences.

“This suggests that while the mice are resting, their brains are making new links between things they have not directly experienced together,” Dupret says, “and we think it’s this process that will help them make useful decisions in the future.”

The result suggests the process is very similar in people and that has important implications, Barron adds. “It suggests that periods of rest and sleep play an important role in creativity, where we draw insight from previous experience to come up with original ideas.”