SINGAPORE: Chronic stress can have a negative effect on decision-making, according to a study by scientists from the Massachusetts Institute of Technology (MIT).
The study, which was published in the journal Cell, builds on research by the same team two years ago.
In their experiments on stressed mice and rats, the animals were far more likely to opt for dangerous alternatives with a bigger reward.
The scientists found that making decisions in this type of situation, known as a cost-benefit conflict, is dramatically affected by chronic stress.
The cause of this abnormal decision-making was impairments of a brain circuit that lie in the striatum, an area involved in planning and decision-making, and for linking action and reward. The circuit integrates information about the good and bad aspects of possible choices to help the brain to produce a decision.
Normally, when this brain circuit is turned on, neurons activate high-firing interneurons, which then suppress striosomes. But when the animals are stressed, a shift occurs and the neurons fire too late to inhibit the striosomes, which then become overexcited. This results in abnormal decision-making. Once this shift occurs, it remains in effect for months.
Senior author Professor Ann Graybiel said: "It is as though the animals had lost their ability to balance excitation and inhibition in order to settle on reasonable behaviour".
But the researchers were able to restore normal decision-making in the stressed mice and rats by using optogenetics to stimulate the high-firing interneurons and suppress the striosomes.
The study's co-author Dr Alexander Friedman said: "This state change could be reversible, and it is possible in the future that you could target these interneurons and restore the excitation-inhibition balance".
According to the authors, the findings could lead to treatments for anxiety and depression, and for reducing the effects of stress to help people avoid bad and sometimes life-altering decisions.