In the rat world, according to a new study, chronic stress rearranges wiring in the brain. One result is poor decision-making, a curse in any species and in any context. Many studies show that humans are more likely to make poor decisions when subjected to unrelieved stress. The rat study helps explain the phenomenon, while reinforcing the case for designing tasks and workplaces ergonomically to control the triggers for stress.
The long list of triggers for employees includes arbitrary change, and that proved to be one of several potent stressors for the rats in the study.
Scientists at the University of Minho in Portugal and the United States National Institutes of Health (NIH) in Maryland observed in an article published in the July issue of Science, the journal of the American Association for the Advancement of Science, that “the ability to shift between different behavioral strategies is necessary for appropriate decision-making.” The stressed rats in the study appeared to lack that ability.
As reported in the publication ScienceNOW Daily News, the rats in one test were taught to hit a lever to score one of two possible treats: a sip of a sugary solution or a food pellet. The scientists then changed the rules by giving the rats all the snacks they wanted before giving them the option to press the lever. Unstressed, satiated rats hit the lever significantly less, while stressed rats continued pressing at the same rate.
The rodents were trained to use two levers for another of the tests, one for each treat. After the rats learned the rules, the researchers picked one treat to dispense randomly, whether or not the rat hit the lever. The relaxed animals hit that treat’s lever less often, while the stressed rats continued to hit both levers with equal frequency.
When the scientists studied a region of the rats’ brains called the dorsal striatum, they found striking differences between the two groups. In stressed rats, neurons in the dorsomedial striatum, an area associated with goal-directed behavior had shrunk, making fewer connections to other cells. Meanwhile neurons in the dorsolateral striatum, an area that controls habits, had grown and formed more branches. The researchers concluded that chronic stress rewires brain areas involved in the switch between goal-directed and habitual actions.
The switch to rote decision making can be "highly detrimental" when inhibiting the ability to adapt to changing environments, wrote lead author Eduardo Dias-Ferreira of the University of Minho, as reported in AFP. It also "has a broader impact spanning activities from everyday life decisions to economics."
Sources: Science; ScienceNOW Daily News; AFP