New Experiences Improve Learning

The ability to adapt to new situations is quite important in terms of survival. This flexibility is impaired in many neuropsychiatric disorders. It is important to understand how new experiences affect the brain circuits to facilitate cognitive flexibility.

A study conducted on rats demonstrates that being exposed to new experiences enabled the rats to learn new navigation strategies by decreasing the stationary representations in the hippocampus and prefrontal cortex.

The effects of being exposed to a new experience

Spatial learning depends on the circuit between the ventral hippocampus and the medial prefrontal. The connection between these brain structures become stronger throughout the spatial learning process. On the other hand, if the connection remains at maximum power, this makes it difficult to adapt to new duties and tasks at a later stage. Researchers assumed that being exposed to a new experience reduces the stationary hippocampal-prefrontal connection, and that it could function as an environmental trigger enabling flexible spatial learning.

In the first task within the scope of the research, the rats were trained to walk around a labyrinth to get rewards. While some rats were allowed to explore a place that they had never seen before, the others were allowed to walk around an ever-familiar place. At the next stage, the rats were engaged in a task that required transition to a new navigation strategy in order to get a reward. As expected, all rats initially preferred their original navigation strategies. Nevertheless, the rats that previously explored a new area gradually left behind the first strategy they learned, and then they successfully managed to learn the new navigation strategy by the half of the 40 sessions of attempt for the training.

Researchers found that the rats being exposed to novelty updated their strategies based on what the task demanded, and that they were able to go back to their original strategy when needed. Moreover, following the analysis of the records taken from the ventral hippocampus, they discovered that the theta wave improved during the exploration and throughout the hours after that; nevertheless, they saw a reduction in the theta wave in two consecutive days as the rats became accustomed to the area.

At the same time, the neurons in the medial prefrontal cortex demonstrated a reduced theta wave synchronization, while the correlations between the hippocampal activity and prefrontal activity weakened. These and other findings show that being exposed to novelty reduced the synaptic connections between the ventral hippocampus and the medial prefrontal cortex, and that it reset the circuit to enable the learning-specific connection to be strengthened later on.

Exposing rats to novelty weakened the vHPC-mPFC connection by re-regulating the vHPC activity based on theta (4-12) oscillations, and it deteriorated a pre-coded strategy. When the rats adapted to a new task later on, the vHPC neurons developed an activity that was related to the new task, improved the vHPC-mPFC connection, while the mPFC neurons were updated to code the new rules.

These results show that new experience supports learning, and enables the plasticity of the circuit that is related to the next learning activity.

REFERENCES:
– Alan J. Park; Alexander Z. Harris; Kelly M. Martyniuk; Chia-Yuan Chang; Atheir I. Abbas; Daniel C. Lowes; Christoph Kellendonk; Joseph A. Gogos; Joshua A. Gordon. Reset Of Hippocampal–Prefrontal Circuitry Facilitates Learning. Nature, DOI: 10.1038/s41586-021-03272-1

– New experiences enhance learning by resetting key brain circuit. National Institute of Mental Health (NIMH)