The researchers worked, precisely, on a key information processing center, the ventral pallidum, of the mouse brain. The goal was to better understand how neurons and neural circuits manage these opposite behavioral motivations. Research shows that different types of neurons control “positive” and “negative” motivation, sending opposite signals along a brain circuit dedicated to processing motivation. Ultimately, the balance of activity between these two groups of cells helps to determine whether a person is more in search of pleasant experiences or rather in avoiding negative experiences.
Rather looking for pleasure or avoiding any pain?
The pleasure-pain balance is disturbed in the event of mental disorder: Initially, the lead author, Professor Bo Li of CSHL found in clinical practice that the balance between these two behaviors is frequently upset in patients with mental illness. For example, people with depression can stop doing things that once made them happy, and patients with anxiety disorders can go to extremes to avoid any possible threats.
The ventral pallidum is the key area of the brain that manages this ability to recognize and assess the possible rewards or sanctions associated with certain behaviors. Researchers actually observe activity in this area when animals seek rewards, such as a sip of water, or avoid punishment, such as an annoying breath of air. But how do the different types of neurons in the ventral pallidum guarantee a balanced response to the signals associated with the 2 types of motivation? Using cutting-edge techniques, researchers find that:
- the neurons which use the neurotransmitter GABA to dampen the activity in the circuit involved in motivation motivate the mice to seek a reward;
- neurons that use the neurotransmitter glutamate to excite the same brain circuit help avoid the penalty.
- in more complex situations, with both a prospect of reward and a risk of sanction, animals are very capable of compromise: a balance is created between the activity of the 2 types of neurons. But when researchers artificially modify this balance in the ventral pallidum by manipulating one class of neurons or the other, they are then able to modify the behavior of animals.
This balance between pleasure and pain or reward and punishment is very essential to control our decisions and our behavior. And this balance seems disturbed in people suffering from psychiatric disorders: ” behavioral abnormalities in patients with depression or stress-induced anxiety may be caused by changes in this circuit “, Confirm the researchers who come by identifying these processes, to open a new avenue of research and treatment of many mental disorders characterized by excesses in the search for pleasure or the avoidance at all costs of painful experiences.