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By
David F. Salisbury
February 12, 2002
Are you moody? If so, then there is
a small area near the front of your brain - an inch or two behind
your right eye (if you are right handed) - that is probably working
overtime.
That is the conclusion of a new study,
published Feb. 12 in the online Early Edition of the Proceedings
of the National Academy of Sciences, which found a significant association
between activity in a specific area of the brain and individual
differences in mood.
"There are lots of beliefs about the
relationship of individual differences in emotional behavior and
brain function, but this is one of the first times we've seen direct
evidence of an association with a specific brain region," says David
H. Zald, assistant professor of psychology at Vanderbilt University,
who co-authored the paper with Dorothy L. Mattson from the Minneapolis
Veterans Affairs Medical Center and José V. Pardo from the University
of Minnesota.
The study used the brain imaging technique
called positron emission tomography (PET) to record the levels of
brain activity in two groups totaling 89 individuals. The subjects
ranged in age from 18 to 55 years, with a median age in the mid-20s.
There were slightly more men than women. None of the participants
had a history of medical or neurological problems or were using
mood-affecting medicines. They were all right-handed, because of
potential differences in the brains of left- and right-handers.
Before the brain scans were taken,
the individuals filled out a questionnaire that asked them a series
of questions about the extent to which they had experienced unpleasant
moods during the previous month. They then used these answers to
rate each individual on a "negative affect" scale. Negative affect
is a technical term that includes a range of unpleasant mood states,
ranging from irritability to anxiety to anger. Previous studies
have established the reliability of the negative-affect scale and
have shown that individuals who rate high on the scale are at increased
risk of developing depression or anxiety disorders.
After scanning the first group of 51
subjects, the researchers compared the levels of brain activity
of all the subjects. They looked for areas where the activity level
varied in accordance with patients' rating on the negative affect
scale, showing either increasing or decreasing activity levels in
those with higher negative-affect ratings.
"The most striking positive correlation
we found was localized in only one small region of the brain, the
ventromedial prefrontal cortex," says Zald. "Because this is just
a correlation, we don't know whether this activity is the cause
or the effect of negative mood states. Such a connection does make
sense, however, because animal studies show that this region of
the brain controls heart rate, breathing, stomach acidity levels,
sweating and similar autonomous functions that have a close connection
to mood."
In order to double-check their findings,
the researchers assembled a second group of 38 subjects. They put
them through the same procedure and came up with essentially the
same results: the variation of activity associated with differences
on the negative affect scale account for about 20 percent of the
total variation in the activity levels measured in the region.
Since the time of the ancient Greeks,
there has been speculation that the brain is the basis of personality,
but it is only within the last 20 years that scientists have developed
instruments capable of measuring brain activity with enough accuracy
to address this question directly.
"With increased knowledge of the relationship
between brain function and mood, we should be able to find more
effective ways to treat the millions of Americans who suffer from
clinical depression each year," says Zald.
David Zald's home page:
http://www.psy.vanderbilt.edu/faculty/zalddh/zaldhomepage.htm
David Zald research description:
http://bret.mc.vanderbilt.edu/neuroscience/cfm_files/view_facname.cfm?KeyNo=286
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