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subliminal responses to fleeting images of fearful faces

Allen L. Barker alb at datafilter.com
Thu Dec 23 19:00:46 EST 2004



FLEETING IMAGES OF FEARFUL FACES REVEAL NEUROCIRCUITRY OF UNCONSCIOUS 
ANXIETY
http://www.cumc.columbia.edu/news/press_releases/hirsch_kandel_etkin_anxiety_neuron.html

New York, December 15, 2004 – Researchers at Columbia University 
Medical Center have found that fleeting images of fearful faces – 
images that appear and disappear so quickly that they escape conscious 
awareness – produce unconscious anxiety that can be detected in the 
brain with the latest neuroimaging machines.

It’s one of the first times that neuroimaging has captured the brain’s 
processing of unconscious emotion.

Using a high-resolution version of functional magnetic resonance 
imaging (fMRI) the researchers observed a structure in the brain 
important for emotional processing - the amygdala - lights up with 
activity when people unconsciously detected the fearful faces.

Although the study was conducted in people who had no anxiety 
disorders, the researchers says that the findings should also apply to 
people with anxiety disorders.

“Psychologists have suggested that people with anxiety disorders are 
very sensitive to subliminal threats and are picking up stimuli the 
rest of us do not perceive,” says Dr. Joy Hirsch, professor of 
neuroradiology and psychology and director of the fMRI Research Center 
at Columbia University Medical Center, where the study was conducted. 
“Our findings now demonstrate a biological basis for that unconscious 
emotional vigilance.”

Dr. Hirsch adds that the finding makes a profound prediction: “If a 
treatment for anxiety works, we should see the unconscious activity in 
the input end of the amygdala go down. In future studies, we want to 
use brain imaging to test the effectiveness of psychotherapeutic and 
pharmacological treatments for anxiety disorders.”

The study was led by Drs. Hirsch; Eric Kandel, Senior Investigator at 
the Howard Hughes Institute, and Director of the Kavli Institute for 
Brain Science at Columbia University Medical Center; Rene Hen, 
professor of pharmacology; and graduate students Amit Etkin and 
Kristen Klemenhagen. Their research appears in the Dec. 16 issue of 
Neuron.

About the Study

In the study, the researchers presented images of fearful facial 
expressions, which are powerful signals of danger in all cultures, to 
17 different subjects. None of the 17 volunteers had any anxiety 
disorders, but their underlying anxiety varied from the 6th to the 
85th percentile of undergraduate norms, as measured by a 
well-validated questionnaire.

“These are the type of normal differences that would be apparent if 
these people got stuck in an elevator,” Dr. Hirsch says. “Some of them 
would go to sleep; some would climb the walls.”

While the subjects were looking at a computer, the researchers 
displayed an image of a fearful face onto the monitor for 33 
milliseconds, immediately followed by a similar neutral face. The 
fearful face appeared and disappeared so quickly that the subjects had 
no conscious awareness of it.

But the fMRI scans clearly revealed that the brain had registered the 
face and reacted, even though the subjects denied seeing it. These 
scans show that the unconsciously perceived face activates the input 
end of the amygdala, along with regions in the cortex that are 
involved with attention and vision.

Brain activity varies with level of anxiety

The researchers also noticed that the amount of brain activity varied 
from person to person, depending on their scores on the anxiety quiz.

The amygdalas of anxious people was far more active than the amygdalas 
of less anxious people. And anxious subjects showed more activity in 
the attention and vision regions of the cortex, which manifested 
itself in faster and more accurate answers when the subjects were 
asked questions about the neutral face.

“What we think we’ve identified is a circuit in the brain that’s 
responsible for enhancing the processing of unconsciously detected 
threats in anxious people,” says Amit Etkin, the study’s first author. 
“An anxious person devotes more attention and visual processing to 
analyze the threat. A less anxious person uses the circuit to a lesser 
degree because they don’t perceive the face as much as a threat.”

Unconscious vs. conscious processing of fearful faces

In contrast to unconscious processing of fearful faces, the 
researchers found that when subjects looked at the fearful faces for 
200 milliseconds, long enough for conscious recognition, a completely 
different brain circuit was used to process the information. And the 
activity in that circuit did not vary according to the subject’s level 
of anxiety.

“Our study shows that there’s a very important role for unconscious 
emotions in anxiety,” Etkin says.


-- 
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Home page: http://www.datafilter.com/alb
Allen Barker



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