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FOR IMMEDIATE RELEASE
Contact: Karen
Zipern
212-305-9746;
kz2110@columbia.edu
FLEETING IMAGES OF FEARFUL FACES REVEAL NEUROCIRCUITRY
OF UNCONSCIOUS ANXIETY
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.
Columbia
University Medical Center provides international leadership in basic, pre-clinical and
clinical research, medical education, and health care. The medical center
trains future leaders in health care and includes the dedicated work of many
physicians, scientists, nurses, dentists, and other health professionals at
the College of Physicians & Surgeons, the School of Dental & Oral
Surgery, the School of Nursing, the Mailman School of Public Health, the
biomedical departments of the Graduate School of Arts and Sciences, and
allied research centers and institutions.
With a strong history of some of the most important advances and
discoveries in health care, its researchers are leading the development of
novel therapies and advances to address a wide range of health conditions
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