Mood changes, even momentary ones, could profoundly heighten the brain's response to pleasure in people having bipolar disorder, according to a research.
People having this mental condition, marked by extreme shifts in moods and energy levels, are more prone to this 'mood bias' - the term researchers used for when one's good mood tends to make them view everything more favourably and hence "gain momentum" in mood.
"Imagine going to a new restaurant for the first time. If you happen to be in a fantastic mood, you're likely to perceive the experience as being even better than it actually is," said Liam Mason, University College London's Psychology and Language Sciences, co-lead author of the study published in the journal Biological Psychiatry Global Open Science.
The findings could help understand why people with bipolar disorder get stuck in a "vicious cycle" in which their mood escalates, sometimes making them take bigger risks than usual, the researchers said.
For the study, the researchers scanned the brains of participants while playing a computerised version of the Roulette game - 21 of them with bipolar disorder and 21 without. Playing the game involves making a gamble as to which compartment of a revolving wheel a small ball will come to rest in.
Using the functional Magnetic Resonance Imaging (fMRI) brain scanning technique, the researchers tracked the brain responses of the participants while winning and losing. They measured how the 'reward signals' in the brains were being influenced by mood changes in a matter of seconds, using computer models. The team found intense activity in the brain's anterior insula - involved in changing moods - in both the groups of participants during the game.
However, only the participants having bipolar disorder showed a heightened influence of 'mood bias' on their perception of wins and losses. In the brain scans, the researchers observed intense activity in the participants' striatum - the region responding to pleasurable experiences.
"In the control group, insula and striatum are both firing up in union, suggesting that participants were better able to keep their 'mood in mind' when perceiving rewards in the task.
"Meanwhile, participants with bipolar disorder showed the opposite; when there was higher momentum, they were less able to set this aside from how exciting they found the rewards to be," said co-lead author Hestia Moningka from the University College London's Psychology and Language Sciences.
The team also found a weaker communication between these brain regions - the anterior insula and the striatum - in the participants with bipolar disorder. The findings could help us move beyond existing interventions aimed at regulating mood often at the cost of dampening down exciting experiences, according to Moningka.
"Instead, new interventions that help people with bipolar disorder to better decouple their mood from their perception and decisions is an avenue we are looking into," said Moningka.
