The science of guessing

Scientists discover what happens in our brains when guessing.

Guessing is the act of estimating or concluding something without sufficient information to be sure of being correct. 

In everyday life, we often infer connections or relationships between different things we see or hear. Even when we don’t know the full story, we can make an educated guess by joining the dots.

These guesses are thought to engage several brain regions; however, the underlying neuronal computation remains unknown.

Now, a new study finds how cells in our brains work together to join up memories of different experiences, allowing us to make educated guesses in everyday life. The study revealed that the process takes place in a region of the brain called the hippocampus.

Scientists studied this ability to an area of the brain called the hippocampus that is already known to play a role in learning and memory. For this, they used MRI scans on people and by temporarily switching off the hippocampus in mice.

Their goal was to determine how brain cells enable us to make educated guesses. To do so, they ran a set of very similar experiments in people and mice.

Human volunteers were asked to play a virtual reality game were hearing a sound, such as running water, signaled that the volunteers would also see a colorful picture appear on the wall. They would then play another game where finding colorful 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.

A similar experiment was conducted on 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 humans, the mice began connecting the sound with the reward.

Their experiments revealed that the process of establishing a link between separate events is common to both species. Also, experiments with mice suggested what’s going on in a mammal brain at the level of individual cells.

Scientists recorded the activity of mice 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 started to fire in that order.

Dr. David Dupret from MRC Brain Network Dynamics Unit at the University of Oxford said, “This suggests that while the mice are resting, their brains are making new links between things they have not directly experienced together, and we think it’s this process that will help them make useful decisions in the future.”

Dr. Helen Barron, also from the MRC Brain Network Dynamics Unit at the University of Oxford, said, “Our results suggest the process is very similar in people and that has important implications. 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.”

Dr. Simon Fisher, Programme Manager for the Neurosciences and Mental Health Board at the MRC, added“Our ability to put individual memories together to form new links helps us make day-to-day decisions. This study provides insight into how and wherein the brain, this key process takes place. It also suggests that while we are sleeping or resting, our brains are actively making these links, a process that may form the basis of creative thinking.”

“This strong approach, of working with mice alongside comparable experiments with people, allows findings from one species to inform studies in the other and enhances the translation of biological knowledge from animal models through to humans.”

Journal Reference:
  1. Helen C. Barron et al. Neuronal Computation Underlying Inferential Reasoning in Humans and Mice. DOI: 10.1016/j.cell.2020.08.035

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