Brain Is a Co-Conspirator in a Vicious Stress LoopBy NATALIE ANGIER
<http://topics.nytimes.com/top/reference/timestopics/people/a/natalie_an\
gier/index.html?inline=nyt-per> Published: August 17, 2009
If after a few months' exposure to our David Lynch economy, in which
housing markets spontaneously combust, coworkers mysteriously disappear
and the stifled moans of dying 401(k)
<http://topics.nytimes.com/your-money/retirement/401ks-and-similar-plans\
/index.html?inline=nyt-classifier> plans can be heard through the
floorboards, you have the awful sensation that your body's stress
<http://health.nytimes.com/health/guides/symptoms/stress-and-anxiety/ove\
rview.html?inline=nyt-classifier> response has taken on a
self-replicating and ultimately self-defeating life of its own,
congratulations. You are very perceptive. It has.
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<http://www.nytimes.com/2009/08/18/science/18angier.html#secondParagraph\
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As though it weren't bad enough that chronic stress has been shown
to raise blood pressure
<http://health.nytimes.com/health/guides/test/blood-pressure/overview.ht\
ml?inline=nyt-classifier> , stiffen arteries, suppress the immune
system, heighten the risk of diabetes
<http://health.nytimes.com/health/guides/disease/diabetes/overview.html?\
inline=nyt-classifier> , depression and Alzheimer's disease
<http://health.nytimes.com/health/guides/disease/alzheimers-disease/over\
view.html?inline=nyt-classifier> and make one a very undesirable dinner
companion, now researchers have discovered that the sensation of being
highly stressed can rewire the brain in ways that promote its sinister
persistence.

Reporting earlier this summer in the journal Science, Nuno Sousa of the
Life and Health Sciences Research Institute at the University of Minho
in Portugal and his colleagues described experiments
<http://www.sciencemag.org/cgi/content/abstract/325/5940/621> in which
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.

Moreover, the rats' behavioral perturbations were reflected by a
pair of complementary changes in their underlying neural circuitry. On
the one hand, 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.

In other words, the rodents were now cognitively predisposed to keep
doing the same things over and over, to run laps in the same dead-ended
rat race rather than seek a pipeline to greener sewers. "Behaviors
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," Dr. Sousa said.
"I call this a vicious circle."

Robert Sapolsky, a neurobiologist who studies stress at Stanford
University
<http://topics.nytimes.com/top/reference/timestopics/organizations/s/sta\
nford_university/index.html?inline=nyt-org> School of Medicine, said,
"This is a great model for understanding why we end up in a rut, and
then dig ourselves deeper and deeper into that rut."

The truth is, Dr. Sapolsky said, "we're lousy at recognizing
when our normal coping mechanisms aren't working. Our response is
usually to do it five times more, instead of thinking, maybe it's
time to try something new."

And though perseverance can be an admirable trait and is essential for
all success in life, when taken too far it becomes perseveration —
uncontrollable repetition — or simple perversity. "If I were to
try to break into the world of modern dance, after the first few
rejections the logical response might be, practice even more," said
Dr. Sapolsky, the author of "Why Zebras Don't Get Ulcers
<http://health.nytimes.com/health/guides/disease/gastric-ulcer/overview.\
html?inline=nyt-classifier> ," among other books. "But after the
12,000th rejection, maybe I should realize this isn't a viable
career option."

Happily, the stress-induced changes in behavior and brain appear to be
reversible. To rattle the rats to the point where their stress response
remained demonstrably hyperactive, the researchers exposed the animals
to four weeks of varying stressors: moderate electric shocks, being
encaged with dominant rats, prolonged dunks in water. Those chronically
stressed animals were then compared with nonstressed peers. The stressed
rats had no trouble learning a task like pressing a bar to get a food
pellet or a squirt of sugar water, but they had difficulty deciding when
to stop pressing the bar, as normal rats easily did.

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.

According to Bruce S. McEwen, head of the neuroendocrinology laboratory
at Rockefeller University
<http://topics.nytimes.com/top/reference/timestopics/organizations/r/roc\
kefeller_university/index.html?inline=nyt-org> , the new findings offer
a particularly elegant demonstration of a principle that researchers
have just begun to grasp. "The brain is a very resilient and plastic
organ," he said. "Dendrites and synapses retract and reform, and
reversible remodeling can occur throughout life."

Stress may be most readily associated with the attosecond pace of
postindustrial society, but the body's stress response is one of our
oldest possessions. Its basic architecture, its linked network of neural
and endocrine organs that spit out stimulatory and inhibitory hormones
and other factors as needed, looks pretty much the same in a goldfish or
a red-spotted newt as it does in us.

The stress response is essential for maneuvering through a dynamic world
— for dodging a predator or chasing down prey, swinging through the
trees or fighting off disease — and it is itself dynamic. As we go
about our days, Dr. McEwen said, the biochemical mediators of the stress
response rise and fall, flutter and flare. "Cortisol
<http://health.nytimes.com/health/guides/test/cortisol-level/overview.ht\
ml?inline=nyt-classifier> and adrenaline go up and down," he said.
"Our inflammatory cytokines go up and down."

The target organs of stress hormones likewise dance to the beat: blood
pressure climbs and drops, the heart races and slows, the intestines
constrict and relax. This system of so-called allostasis, of maintaining
control through constant change, stands in contrast to the mechanisms of
homeostasis that keep the pH level and oxygen concentration in the blood
within a narrow and invariant range.

Unfortunately, the dynamism of our stress response makes it vulnerable
to disruption, especially when the system is treated too roughly and not
according to instructions. In most animals, a serious threat provokes a
serious activation of the stimulatory, sympathetic, "fight or
flight" side of the stress response. But when the danger has passed,
the calming parasympathetic circuitry tamps everything back down to
baseline flickering.

In humans, though, the brain can think too much, extracting phantom
threats from every staff meeting or high school dance, and over time the
constant hyperactivation of the stress response can unbalance the entire
feedback loop. Reactions that are desirable in limited, targeted
quantities become hazardous in promiscuous excess. You need a spike in
blood pressure if you're going to run, to speedily deliver oxygen to
your muscles. But chronically elevated blood pressure is a source of
multiple medical miseries.

Why should the stressed brain be prone to habit formation? Perhaps to
help shunt as many behaviors as possible over to automatic pilot, the
better to focus on the crisis at hand. Yet habits can become ruts, and
as the novelist Ellen Glasgow observed, "The only difference between
a rut and a grave are the dimensions."

It's still August. Time to relax, rewind and remodel the brain.



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