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People generally react negatively to uncertainty,
although the response evoked on individual levels differs in degree.
We are studying the relationship between harm avoidance, a component
of temperament, and the brain’s response to negative, unpredictable
stimuli. We expect to find a positive correlation between the harm
avoidance score of an individual and activation in the amygdala
in response to negative, unpredictable stimuli. In order to measure
harm avoidance, each subject took a modified version of the Temperament
and Character Index (TCI), which contains a series of true/false
questions. To measure their brain response, we used functional magnetic
resonance imaging (fMRI) to scan subjects while they watched a screen
that projected colored disks; the disks indicated whether they would
receive quinine, an unpleasant tasting fluid, and whether they would
receive it in a predictable amount of time. A group analysis using
one-sided t-tests was conducted with SPM99. The following contrasts
were examined: predictable quinine v. no quinine and unpredictable
quinine v. predictable quinine. A correlation test was conducted
for each of the contrasts to determine which activations in the
brain were associated with high harm avoidance scores. After examining
twelve subjects, the predictable quinine v. no quinine contrast
showed activation in the left inferior parietal lobe; in this contrast,
high harm avoidance scores correlated with increased brain activity
in the left superior temporal gyrus and the right lingual gyrus.
The unpredictable quinine v. predictable quinine contrast showed
activation in the insula, the left parahippocampal gyrus, the right
superior frontal gyrus, the left inferior frontal gyrus, and the
right precentral gyrus; in this contrast, high harm avoidance scores
correlated with increased brain activity in the left posterior cingulate,
the left precuneus, the right precentral gyrus, the right insula,
and the left claustrum. We conclude that subjects with high harm
avoidance scores correlate with increased insular activity in response
to negative, unpredictable stimuli. To improve this experimentation,
I would like to study the effects of comforting messages, i.e. “Only
one minute left,” on the brain’s response to negative,
unpredictable stimuli. The point of these experiments would be to
relieve fear, not create it.
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