If you have a happy experience… The brain’s ‘anterior thalamus’ plays an important role in long-term memory

Dopamine secretion in the “non-memory” forebrain overturns the current theory

In an experiment to identify areas of the brain associated with memory control, we used the habit of mice that like sugar water. Picture of a pet rat drinking water. Courtesy of Wikimedia

Meanwhile, the ‘anterior thalamus’ of the brain, which is known not to be involved in managing memories, has been found to play an important role in storing memories for a long period of time. As a result of a study observing the brains of mice playing virtual reality (VR) games, it is evaluated that a new secret of the brain related to memory has been identified.

A joint research team of researchers Andrew Toder and Josue Regalado from Rockefeller University in the United States confirmed that the anterior thalamus plays a major role in memory storage in the brain, and research results were published in the international journal ‘Cell’ on the 30th ( local time). The thalamus is an area at the top of the middle brain. This is where sensory information is received and transmitted to the parts responsible for processing information.

How quickly forgotten memories and permanent memories are selected and stored in the brain has been a long-standing interest in academia. The research team explained, “We discovered a new circuit in the anterior thalamus that is responsible for identifying and storing important long-term memories.”

The research team prepared a maze in the VR game space to observe how the mouse brain selects important memories. There are a total of three goal points in the maze, and the reward given to the rat is configured differently depending on the location reached. In the first room, we set up a water jug ​​with unlimited sugar water, which the rats love. The second room has a water bottle provided with only a small amount of sugar water. In the last room, instead of sugar water, I put an empty water container with wind.

The rats who became the test subjects learned the way to each goal point for about three weeks. On the maze path to each room, there were characteristic obstacles that, when touched in the game, provided sound, smell, and visual stimuli in real life, helping the mice to remember the characteristics of each path.

Whether the rat was moving was determined based on memory through the time it took to reach the destination and the time it took the reward. Rats that remembered the way to the room with the better reward took less time to reach the goal. Also, when they reached a bucket of unlimited sugar water, they licked the spout of the bucket for a longer period of time.

The research team confirmed the changes that occur in the brain when the memory behavior of the mouse is observed. Using brain imaging tools, we observed activation patterns of the anterior cingulate cortex (ACC), hippocampus, and anterior thalamus. The anterior cingulate cortex surrounds the bundle of nerves that connect the left and right hemispheres. Most of these areas were active while the rats were exploring the maze. Among these, activation of the anterior thalamic region was prominent.

In order to accurately investigate the actual effect of each brain region on memory storage, the research team ran the experiment again while suppressing the activity of each region. In the case of the anterior cingulate cortex and the hippocampus, there was no specific change in the memory behavior of the rats when the action was stopped or when the nerve cells in these areas were stimulated and activated. On the other hand, stimulating the anterior thalamus directly improved the rats’ memory abilities. Rats stimulated in the anterior thalamus remembered not only the route to the destination with the best reward, but also routes to other rooms with less reward.

The research team explained that a beneficial experience promotes the secretion of adrenaline and dopamine, neurotransmitters that give a feeling of happiness, in the anterior thalamus. Through this, it selects important memories that need to be stored for a long time.

Donga Science Reporter Park Jeong-yeon