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Sci Tech
Holding the prefrontal responsible
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 study, published in 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 beliefs about the relationship of individual differences in emotional behaviour and brain function, but now we've seen direct evidence of an association with a specific brain region," says David H. Zald, assistant professor of psychology at Vanderbilt University.
The study used brain imaging technique — positron emission tomography (PET) to record brain activity in two groups. None of the participants had neurological problems or used 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' includes a range of unpleasant mood states..,
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 subjectsthe 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.
Because this is 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, 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.
To double-check the researchers assembled a second groupof 38 subjects. They put them through the same procedure and got the same results: the variation of activity associated with differences on the negative affect scale account for about 20 per cent of the total variation in the activity levels measured in the region..
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