Stress hormones switch off brain regions for goal-directed behavior

July 26, 2012

chocolate and oranges

Image: Composite Creative Commons Lee McCoy & Kyle McDonald

Ruhr University
Why stressed people fall into habits rather than to act purposefully, cognitive psychologists have discovered the Ruhr-University and their colleagues at the University Hospital Bergmannsheil (Prof. Dr. Martin Tegenthoff). The team led by Dr. Lars Schwabe and Professor Oliver Wolf of the Institute of Cognitive Neuroscience seized drugs with a stressful situation for the body. Then she studied with functional magnetic resonance imaging of brain activity. In the Journal of Neuroscience, the researchers report that the interaction of the stress hormones cortisol and norepinephrine drove down the activity of brain regions for goal-directed behavior. The brain regions that are responsible for habit-based behavior remained unaffected

Two stress hormones in action

To test the effect of various stress hormones, cognitive psychologists put the three ingredients: a placebo, the stress hormone cortisol and Yohimibin, which ensures that the stress hormone norepinephrine remains active longer. A portion of the subjects received only cortisol or just Yohimibin, other volunteers, both substances. The fourth group received a placebo. Overall, the data were received from 69 subjects in the study.

Targeted behaviors and habits examined experimentally

In the experiment, all participants learned that they were given cocoa or orange juice as a reward when they clicked on the computer certain symbols. After this learning phase, subjects were either so many orange or chocolate pudding eating so much as they wanted. “It weakens the value of the reward,” says Schwabe. “Anyone who eats chocolate pudding for the chocolate loses its appeal. . Who is saturated with oranges, has less craving for orange juice Targeted act “in this context: Who has eaten chocolate pudding in the subsequent test series, the less clicks on icons that lead to a reward with cocoa. Who has been eating oranges, opts for rare symbols that are associated with orange juice. Based on previous findings, the scientists took part in that only the combination of cortisol and Yohimibin goal-directed behavior weakens. This hypothesis is confirmed it now.

The mix: Combined effect of cortisol and Yohimibin

As expected, behaving subjects taking Yohimibin and cortisol, not purposefully, but acted according to their habits. The saturation of orange and chocolate pudding had therefore no effect. Persons who had taken only a placebo, or only one of the drugs acted, however, targeted, then showed a saturation effect. The brain data were: the combination of cortisol and Yohimibin is the activity in the forebrain down – the so-called orbitofrontal and medial prefrontal cortex. These areas have been associated in previous studies of goal-directed behavior. The brain regions that are important to the habit of learning were, however, in all subjects equally active.

L. Schwabe, M. Tegenthoff, O. Höffken, O.Wolf (2012): Simultaneous glucocorticoid and noradrenergic activity disrupts the neural basis of goal-directed action in the brain humans, Journal of Neuroscience, doi: 10.1523/JNEUROSCI.1304-12.2012

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