The pleasure and reward system is one of the most important systems governed by the brain.
It spurs us to enjoy the activities that have contributed to our survival as a species, such as eating, drinking, and having sex, so that we feel motivated to pursue them.
The activity of the reward system, however, is also a key factor in various types of addictive behavior.
Now, a team of researchers from the University of Maryland School of Medicine in Baltimore — led by Prof. Scott Thompson, Ph.D. — has discovered that brain regions involved in addiction may also play a role in depression, albeit in an opposite way.
The researchers, who recently published their findings in the journal Nature, identified an increased strength of signals sent between the hippocampus and the nucleus accumbens — two brain regions that form part of the reward system — as a sign of addiction.
“These two parts of the brain are known to be important in processing rewarding experiences,” notes Prof. Thompson. “The communication between these regions is stronger in addiction, although the mechanisms underlying this were unknown,” he adds.
In the current study, the team also tested a new idea, namely whether the same signals grew weaker in people with depression.
“We also suspected that opposite changes in the strength of this communication would occur in depression. A weakening of their connections could explain the defect in reward processing that causes the symptom of anhedonia [a loss of pleasure in usually pleasurable activities] in depressed patients.”
Prof. Scott Thompson
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