FLEETING IMAGES OF FEARFUL FACES REVEAL NEUROCIRCUITRY OF UNCONSCIOUS
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.
Its one of the first times that neuroimaging has captured the brains
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
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
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
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 weve identified is a circuit in the brain thats
responsible for enhancing the processing of unconsciously detected
threats in anxious people, says Amit Etkin, the studys 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 dont 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 subjects level
Our study shows that theres a very important role for unconscious
emotions in anxiety, Etkin says.
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