The findings show that people whose brains are more attuned to rewards may be protected from the negative mental health effects of poor sleep. In fact, study participants with poor quality sleep were less likely to have symptoms of depression if they exhibited greater activity in a reward-sensitive region of the brain.
“This helps us begin to understand why some people are more likely to experience depression when they have problems with sleep,” said Dr. Ahmad Hariri, a professor of psychology and neuroscience at Duke University. “This finding may one day help us identify individuals for whom sleep hygiene may be more effective or more important.”
The study focused on the ventral striatum (VS), a brain region which helps regulate behavior in response to external feedback. The VS helps reinforce behaviors that are rewarded, while reducing behaviors that are not.
In previous work, electrical stimulation of the VS has been found to lower symptoms of depression in patients who do not respond to other forms of treatment; and earlier studies by Hariri’s team show that individuals with higher reward-related VS activity are more resilient to stress.
“We’ve shown that reward-related VS activity may act as a buffer against the negative effects of stress on depressive symptoms,” said Dr. Reut Avinun, a postdoctoral researcher in Hariri’s group at Duke and the lead author of the study. “I was interested in examining whether the same moderating effect would also be seen if we look at sleep disturbances.”
For the study, the researchers examined the brain activity of 1,129 college students participating in the Duke Neurogenetics Study. Each student completed a series of questionnaires to measure sleep quality and depressive symptoms and underwent an fMRI scan while engaging in a task that activates the VS.
During the task, participants were shown the back of a computer-generated card and asked to guess whether the value of the card was greater than or less than five. After they guessed, they received feedback on whether they were correct or not. But the game was rigged, so that during different trials the students were either right 80 percent of the time or wrong 80 percent of the time.
To determine whether general feedback, or specifically reward-related feedback, buffers against depression, the researchers compared VS brain activity during tests when the participants were mostly right to those when they were mostly wrong but still received feedback.
They discovered that students who were less vulnerable to the negative effects of poor sleep showed significantly higher VS activity in response to positive feedback or reward compared to negative feedback.
“Rather than being more or less responsive to the consequences of any actions, we are able to more confidently say it is really the response to positive feedback, to doing something right, that seems to be part of this pattern,” Hariri said.
“It is almost like this reward system gives you a deeper reserve,” Hariri said. “Poor sleep is not good, but you may have other experiences during your life that are positive. And the more responsive you are to those positive experiences, the less vulnerable you may be to the depressive effects of poor sleep.”
The findings are published in The Journal of Neuroscience.
Source: Duke University