Decision-making involves a specific region of the brain, which neuroscientists at MIT have explored further in mice.
You have necessarily already been obliged or obliged to make choices whose costs and benefits you had to weigh. This decision-making process, in a context of uncertainty as in a context that you control, can plunge into deep disarray. But what is going on in your brain during those long seconds? MIT neuroscientists published on March 22, 2022, in Nature Communicationstheir research results on this decision-making process.
Their work identifies the neurons involved in the analysis of the various results of decision-making. These neurons help us assess costs and benefits, but not quite as the researchers expected, because the unexpected plays a major role.
The brain gathers potential outcomes
For this study, the authors trained mice to turn a wheel to the left or to the right. Each side had a positive (sugar water) or negative (a puff of air) result. The mice learned to maximize their chances of getting the positive result by turning the wheel the right way, except that the authors regularly changed the probability that this or that result would be obtained by turning the wheel in this or that direction. The mice therefore had to constantly adapt their decision-making.
During the experiment, neuroscientists monitored what was happening in the mice’s striatum. This region of the brain is already known to be an important center in decision-making, since it governs involuntary movements, but also the entire reward and reinforcement system. This system provides the “motivation” for appropriate actions and behaviors (obtaining pleasure, avoiding displeasure; obtaining the reward, avoiding punishment; learning).
It is for this reason that these neuroscientists recorded the brain activity of the striatum during this experiment, hoping to identify the precise neurons involved in the differentiation between the good action and the bad action, and thus leading to the final decision. . They were able to identify neurons that function this way, because there are indeed some, but they also discovered another mechanism.
“Much of this brain activity is regarding surprising results”
A group of neurons called striosomes, apparently very active during the process, seem responsible for identifying sorts of “error reports”. These are neurons responsible for encoding the relationship between actions and results, and they react especially when faced with an unexpected result — when by turning the wheel in one direction, the result was different from the one usually obtained. It is these error signals that help the brain to adapt its behavior towards the most positive decision.
For the authors, this finally seems quite logical: “ Much of this brain activity is regarding surprising results, because if a result is expected, there is nothing to learn. “, explains the neuroscientist Bernard Bloem, on the MIT website. « What we find is that there is a strong encoding of both unexpected rewards and unexpected negative outcomes. »
The striosomes therefore keep a record of the “actual results”. Then the decision to carry out or not an action, which requires integrating all of these results, ” probably occurs somewhere downstream in the brain ».
If you have to choose between an unhealthy but delicious food and a healthier but less fond food, your striatum knows why these foods are good, and knows the benefits and cost of each “. The resulting neuronal activity in this region “ reflects the potential outcome much more than the mere likelihood of you choosing it “. The decision stems from the evaluation of these potentialities.
