A new study recently published in the journal Science has provided clarity on the mechanism in the brain that keeps us motivated in the pursuit of our goals, causing us to take the necessary actions.
As humans, we take certain actions because of the reward we hope to get from doing them. Not much was known, however, on what is happening in the brain that makes us take actions or behave in a certain way.
New research done using mice at the Friedrich Miescher Institute for Biomedical Research has provided insight into the neuronal mechanism that regulates our motivation to take action.
The amygdala and motivation
A region of the brain known as the amygdala has been known to play a role in motivation. It controls what is known as goal-directed behavior – behaving in a particular way because of the expected reward.
When we choose to take certain actions instead of others, it is usually because of what we think the preferred actions would bring us. If we are to find that we would not get the same reward anymore, we are likely to stop acting the way we have been. This is goal-directed behavior.
Researchers have studied the part that the amygdala plays in cue-directed behavior in mice before now. This is a type of behavior that is driven by cues, such as an auditory or visual cue. For instance, a mouse could be trained to know that something is about to happen when it hears a sound and so be conditioned to behave in a specific way.
However, it was not known how the amygdala controls behavior in a manner aimed at achieving a goal without the use of cues. The current study throws more light on the underlying mechanism.
Exposing the neuronal mechanism
Julien Courtin, a postdoctoral researcher in the lab of Andreas Lüthi, trained mice in a task aimed at goals over several days. He taught the animals to know that when they press a lever they get sucrose and another they receive a drop of milk.
Courtin adapted the setup when the mice got used to performing the tasks. He enabled them to get the reward without pressing a lever or made them press the lever without getting a reward. Separately, the postdoc also allowed the animals to get as much of one of the rewards as they wanted.
While these different tasks were being performed, the researchers recorded the activity in the mice’s amygdala. They observed the diverse neuron groups in the almond-shaped cell cluster that were involved in the different facets of goal-directed behavior.
The team found that a particular group of neurons were active when pressing Lever 1 was expected to bring reward 1. These neurons, however, lost their activity when pressing the lever did not bring the reward anymore.
It was also observed that it was not just the reward, its size, or the chance of getting that mattered. The amygdala also takes note of the value – for instance, the extent of hunger being experienced.
The amygdala transfers information to other regions of the brain. The information is then processed to drive appropriate decisions and regulate behavior in light of the reward.
These findings can be used to explain human behavior as well. We do a lot of things daily because of what we expect to get. And when we do not get our expectations, we are likely to do less of associated actions or stop them altogether.
The same neuronal mechanism revealed in this study is also responsible for our goal-directed behavior as humans. This discovery could aid research into mental disorders, such as depression or addiction.