Be careful, we are talking about animal studies. But there is no doubt that explaining why some subjects are more ready to respond to sudden challenges and others take longer and have greater difficulties represents a real scientific “chichane” for those who deal with behavior. Well, precisely on this front from Nature Communications comes a key to understanding of great interest. In fact, research on experimental animals shows that in the presence of an unexpected change in situations, their brain released more acetylcholine, helping them to change strategy instead of repeating old behaviors.
Use for care
There are many situations in which the ability to adapt leads to “victory”. Whether it’s facing a job interview, meeting someone for the first time or responding to an unexpected challenge, success can be linked precisely to the ability to adapt one’s behavior.
The study, conducted by experts at the Okinawa Institute of Science and Technology (OIST), goes some way to explaining how the brain finds its way back. It all happens thanks to a key brain mechanism that helps animals adapt when circumstances suddenly change. The results, however, could not only have an impact in the professional field but also favor new approaches for those pathological conditions linked to the difficulty in changing habits, including addiction, obsessive-compulsive disorder and Parkinson’s disease.
The brain mechanisms underlying behavioral change have long remained elusive, because adapting to a given situation is a neurologically very complex process. The researchers point out that behavioral flexibility involves a much broader network than a single neurotransmitter or brain cell type. Different brain regions and chemical signaling systems work together to help animals and humans adapt to changing situations. In addition to advancing basic neuroscience, the research could in the future contribute to better treatments for neurological and psychiatric disorders.
“Acetylcholine levels are often altered in treatments for neuropsychiatric disorders such as Parkinson’s disease or schizophrenia, so understanding the function of this neurotransmitter is essential to the treatment of many neuropsychiatric disorders. In particular, in conditions such as addiction and obsessive-compulsive disorder, we find difficulty breaking habits and changing behavior. Therefore, understanding the mechanisms of behavioral flexibility could one day help us develop better treatments.”
reports one of the authors of the study, Jeffery Wickens.
The role of acetylcholine
There are specific brain neurons called cholinergic, which release a neurotransmitter called acetylcholine. It has long been known that these come into play in the adaptation of subjects to behaviors. The study goes further: it allows us to observe the release of the neurotransmitter in real time and delve deeper into the fundamental mechanisms underlying behavioral flexibility.
The researchers first trained mice to orient themselves in a virtual maze. The animals learned which path would lead to a reward and gradually developed a reliable strategy for reaching it. Then the rules changed and the reward path changed. Suddenly the animals didn’t get what they expected. Using two-photon microscopy, the researchers monitored the animals’ brain activity as they reacted to this surprising result.
“On a neural level, we observed a significant increase in the release of acetylcholine in some areas of the brain. On a behavioral level, we noticed that a greater number of mice showed the so-called ‘change of strategy on loss’ behavior, changing their choices in the maze after not obtaining a reward”
comments Gideon Sarpong, first author of the study.
Thus habits change
The study also shows another quantitative aspect that should not be underestimated: the greater the increase in acetylcholine, the greater the probability that the mice changed their future choices. In short: thanks to acetylcholine, habits can be changed, on a path that leads to resilience.
To test whether acetylcholine was actually responsible for this behavioral flexibility, the team reduced the animals’ ability to produce the neurotransmitter. The effect was evident. The mice showed much less strategy-switching behavior in the event of a loss, making them less likely to change their decisions after an unexpected outcome. The findings confirmed that acetylcholine plays an essential role in helping the brain adapt when circumstances change.
Interestingly, not all groups of cholinergic interneurons reacted the same way. While most released more acetylcholine, some small groups of cells showed little change or even a decrease in activity. According to the researchers, this could help preserve information about previously effective behaviors. In short: mice may not necessarily forget the previous route to the reward, but retain this information in case the situation changes again.
