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Inducing Paranoia Leads to Resting Amygdala Hyperactivity in Healthy Individuals
Objective: Among individuals with schizophrenia, paranoia has been linked to increased resting cerebral blood flow (CBF) in amygdala, suggesting that amygdala hyperactivity may be a mechanism for paranoid ideation. The present study tested this possible mechanism by assessing whether experimentally inducing paranoia in non-clinical participants resulted in increased amygdala CBF. Methods: Healthy undergraduates (n=63) completed an initial assessment of resting CBF via arterial spin labeling imaging. Participants were then randomly assigned to either a paranoia induction (n=32) or control (n=31) condition lasting approximately 30 minutes and then scanned again. Resting CBF values were extracted from right and left amygdala and analyzed using repeated measures ANOVA with time (within-subjects) and group (between-subjects) as independent variables. Results: While the group by time interaction in right amygdala did not reach statistical significance (p=.07), individuals in the paranoia induction condition showed increased resting CBF in right amygdala at post-induction relative to pre-induction (p=.04). In contrast, individuals in the control cognition showed decreased resting CBF over time (p=.04). Left amygdala showed no significant effects. Conclusions: These results support the idea that increased tonic activity of the amygdala may be a neurobehavioral mechanism for paranoia and the over-attribution of threat to benign stimuli.