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Brain & Nervous System Health Center

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Second Thoughts Are Real

Little Voice That Says 'Stop' Found in Brain
WebMD Health News
Reviewed by Louise Chang, MD

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 London.

"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 the button.

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 region.

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