Second Thoughts Are Real
Little Voice That Says 'Stop' Found in Brain
Aug. 21, 2007 - The a little voice in your head that warns you not to do
something you were just about to do is real, brain researchers say.
Well, maybe not the voice. But researchers now say last-minute second
thoughts come from a specific part of the brain.
A different area of the brain allows us to act voluntarily. That's free
will. This is "free won't," suggest Marcel Brass, PhD of Germany's Max
Planck Institute and Patrick Haggard, PhD, of England's University College
"Many people recognize the 'little voice inside the head' that stops you
from doing something, like pressing the 'send' button on an angry email,"
Haggard says in a news release. "Our study identifies the brain processes
involved in that last-minute rethink about what we are doing."
Brass and Haggard find that a brain region just above and between your eyes
-- the dorsal fronto-median cortex or dFMC -- is specifically designed to let
you pull back from doing something you were just about to do.
University of Pennsylvania researcher Martha Farah, PhD, says the findings
have major implications. Farah was not involved in the study.
"It is very important to identify the circuits that enable 'free won't'
because of the many psychiatric disorders for which self-control problems
figure prominently -- from attention deficit disorder to substance dependence
and various personality disorders," Farah says in a news release.
In their study, Brass and Haggard hooked up 15 healthy young adults to
functional MRI machines that did real-time scans of their brain activity. The
participants were asked to decide to push a button at times of their own
choosing. Some of the time the participants were asked to decide at the last
minute not to push the button.
Brain scans taken when the participants actually pushed the button were
different from those taken when the subjects restrained themselves from pushing
This self-control came at a cost. The subjects reported feeling frustrated
when they did not push the button as they had intended to do. That fit with
their brain scans; a part of the brain linked to feelings of frustration (the
anterior ventral insula) lit up along with the dFMC "free-won't" brain
Interestingly, some of the study participants were less likely to refrain
from pushing the button than others. These subjects had relatively weak dFMC
activity, while those with better self-control had stronger dFMC activity.
"This could be a factor in why some individuals are impulsive, while
others are reluctant to act," Haggard says.
Brass and Haggard report their findings in the Aug. 22 issue of the
Journal of Neuroscience.
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