Researchers have zeroed in on an information-processing hub from the mind to discover how neurons balance pleasure and pain.
The research by New York-based Cold Spring Harbor Laboratory (CSHL) demonstrated that different classes of neurons control positive and negative motivation, delivering conflicting signs as well as a shared motivation-processing brain circuit. Ultimately, the balance of activity between both of these groups of cells can determine if someone acts to find pleasurable experiences or avoid negative ones, says Professor Bo Li who headed the study reported in the journal Neuron. The group wanted to understand the brain’s motivation-processing circuits because the behaviors they control are often disrupted in people with mental illness.
“Behavioural changes in people with depression or stress-induced anxiety may be caused by changes in this circuit,” Li said.
The capacity to recognize and respond to potential benefits or punishments depends in part on a part of the brain called the ventral pallidum.
Researchers have observed activity in this brain area when animals seek benefits, like a sip of water, or avoid punishments, like an annoying puff of air. After training mice to associate certain sounds with a sip of water or a puff of air, Li and his colleagues used the method to monitor neural activity in the ventral pallidum.
They found that neurons that used the neurotransmitter known as GABA to dampen activity in the circuit affecting motivation were significant in motivating the mice to seek a water reward. The neurons that used the neurotransmitter called glutamate to excite the mind circuit, on the other hand, were essential for avoiding the air-puff punishment.
That balance between signs that either excite or inhibit neurons in the ventral pallidum appears critical in controlling which motivation an animal behaves on, Li says. Now, Li is excited to discover whether it’s disrupted in people with psychiatric disorders. With the new findings, his team has leads about how to investigate the causes and symptoms of these disorders more deeply.