How The Brain Works For You While Resting

Humans are particularly good at using generalisations from past experiences to make broad assumptions when they are faced with little information about new experiences.

In a new study, researchers from the University of Oxford, UCL and DeepMind, looked at whether such abstract knowledge affects how we approach new experiences.

It is thought that making these conclusions relies on the models of the world that we create in our mind during everyday experiences, which use the same neural mechanisms and brain cells that help us understand our position relative to other objects and places.

Although encoding our current location, these brain cells also spontaneously recall old memories, and explore new possibilities – a phenomenon known as “replay”.

The researchers trained participants in a task defining and ordering everyday objects, and then presented a new set of familiar objects in a scrambled order - during which they applied a device to map brain activity in the participants.

They observed that the ordering of the new objects was reactivated during subsequent rest, and these ‘replay‘ events occurred much faster than in their actual presentation.

Human replay occurs while the brain is resting between exercises, and events are played out in reversed direction, after a reward has been given for making the correct choice.

Professor Timothy Behrens of Oxford’s Nuffield Department of Clinical Neurosciences, said: “Replay plays out events in a different order to the order they were seen in, which is a sophisticated jump for the brain to make. A defining feature of human intelligence is the ability to make strong inferences on the basis of sparse observations. If you notice your husband’s wallet on the kitchen table, you immediately know he is more likely to be in the garden than the pub. It is completely unknown how such inferences are performed in our brains, but our research suggests an important role for replay.”

They also found that replay is factorised - that is, multiple representations of different aspects of events are replayed simultaneously, and these different representations can be recombined to make new events. This is important because factorised representations are a powerful means of generalising knowledge.