Memories become labile when recalled. In humans and rodents alike, reactivated fear memories can be attenuated by disrupting reconsolidation with extinction training. Using functional brain imaging, we found that, after a conditioned fear memory was formed, reactivation and reconsolidation left a memory trace in the basolateral amygdala that predicted subsequent fear expression and was tightly coupled to activity in the fear circuit of the brain. In contrast, reactivation followed by disrupted reconsolidation suppressed fear, abolished the memory trace, and attenuated fear-circuit connectivity. Thus, as previously demonstrated in rodents, fear memory suppression resulting from behavioral disruption of reconsolidation is amygdala-dependent also in humans, which supports an evolutionarily conserved memory-update mechanism.

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Cognitive behavior therapy (CBT) is an effective treatment for social anxiety disorder (SAD), but many patients do not respond sufficiently and a substantial proportion relapse after treatment has ended. Predicting an individual's long-term clinical response therefore remains an important challenge. This study aimed at assessing neural predictors of long-term treatment outcome in participants with SAD 1 year after completion of Internet-delivered CBT (iCBT). Twenty-six participants diagnosed with SAD underwent iCBT including attention bias modification for a total of 13 weeks. Support vector machines (SVMs), a supervised pattern recognition method allowing predictions at the individual level, were trained to separate long-term treatment responders from nonresponders based on blood oxygen level-dependent (BOLD) responses to self-referential criticism. The Clinical Global Impression-Improvement scale was the main instrument to determine treatment response at the 1-year follow-up. Results showed that the proportion of long-term responders was 52% (12/23). From multivariate BOLD responses in the dorsal anterior cingulate cortex (dACC) together with the amygdala, we were able to predict long-term response rate of iCBT with an accuracy of 92% (confidence interval 95% 73.2–97.6). This activation pattern was, however, not predictive of improvement in the continuous Liebowitz Social Anxiety Scale—Self-report version. Follow-up psychophysiological interaction analyses revealed that lower dACC–amygdala coupling was associated with better long-term treatment response. Thus, BOLD response patterns in the fear-expressing dACC–amygdala regions were highly predictive of long-term treatment outcome of iCBT, and the initial coupling between these regions differentiated long-term responders from nonresponders. The SVM-neuroimaging approach could be of particular clinical value as it allows for accurate prediction of treatment outcome at the level of the individual.

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IMPORTANCE Serotonin is involved in negative affect, but whether anxiety syndromes, such as social anxiety disorder (SAD), are characterized by an overactive or underactive serotonin system has not been established. Serotonin 1A autoreceptors, which inhibit serotonin synthesis and release, are downregulated in SAD, and serotonin transporter availability might be increased; however, presynaptic serotonin activity has not been evaluated extensively. OBJECTIVE To examine the serotonin synthesis rate and serotonin transporter availability in patients with SAD and healthy control individuals using positron emission tomography (PET) with the radioligands 5-hydroxytryptophan labeled with carbon 11 ([ 11 C]5-HTP) and 11 C-labeled 3-amino-4-(2-dimethylaminomethylphenylsulfanyl)-benzonitrile [ 11 C]DASB. DESIGN, SETTING, AND PARTICIPANTS We performed a cross-sectional study at an academic clinical research center. Eighteen patients with SAD (9 men and 9 women; mean [SD] age, 32.6 [8.2] years) and 18 sex-and age-matched healthy controls (9 men and 9 women; mean [SD] age, 34.7 [9.2] years) underwent [ 11 C]5-HTP PET imaging. We acquired [ 11 C]DASB PET images for 26 additional patients with SAD (14 men and 12 women; mean [SD] age, 35.2 [10.7] years) and the same 18 sex-and age-matched healthy controls. Participants were recruited through newspaper advertisements.