…chronically stressed rats lost their elastic rat cunning and instead fell back on familiar routines and rote responses, like compulsively pressing a bar for food pellets they had no intention of eating. … regions of the brain associated with executive decision-making and goal-directed behaviors had shriveled, while, conversely, brain sectors linked to habit formation had bloomed.

Nuno SousaBehaviors become habitual faster in stressed animals than in the controls, and worse, the stressed animals can’t shift back to goal-directed behaviors when that would be the better approach.

I call this a vicious circle.

Nuno Sousa, MD PhD
Life and Health Sciences
Research Institute

But with only four weeks’ vacation in a supportive setting free of bullies and Tasers, the formerly stressed rats looked just like the controls, able to innovate, discriminate and lay off the bar. Atrophied synaptic connections in the decisive regions of the prefrontal cortex resprouted, while the overgrown dendritic vines of the habit-prone sensorimotor striatum retreated.

–Brain Is a Co-Conspirator
in a Vicious Stress Loop
NYTimes.com




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