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Amygdala function is of high interest for cognitive, social and psychiatric neuroscience, emphasizing the need for reliable assessments in humans. Previous work has indicated unsatisfactorily low within-subject reliability of amygdala activation fMRI measures. Based on basic science evidence for strong habituation of amygdala response to repeated stimuli, we investigated whether a quantification of habituation provides additional information beyond the usual estimate of the overall mean activity. We assessed the within-subject reliability of amygdala habituation measures during a facial emotion matching paradigm in 25 healthy subjects. We extracted the amygdala signal decrement across the course of the fMRI run for the two test–retest measurement sessions and compared reliability estimates with previous findings based on mean response amplitude. Retest-reliability of the session-wise amygdala habituation was significantly higher than the evoked amygdala mean amplitude (intraclass correlation coefficients (ICC) = 0.53 vs. 0.16). To test the task-specificity of this finding, we compared the retest-reliability of amygdala habituation across two different tasks. Significant amygdala response decrement was also seen in a cognitive task (n-back working memory) that did not per se activate the amygdala, but was totally unreliable in that context (ICC ~ 0.0), arguing for task-specificity. Together the results show that emotion-dependent amygdala habituation is a robust and considerably more reliable index than the mean amplitude, and provides a robust potential endpoint for within-subject designs including pharmaco-fMRI studies. [ABSTRACT FROM AUTHOR]

Abstract: Even more than in cognitive research applications, moving fMRI to the clinic and the drug development process requires the generation of stable and reliable signal changes. The performance characteristics of the fMRI paradigm constrain experimental power and may require different study designs (e.g., crossover vs. parallel groups), yet fMRI reliability characteristics can be strongly dependent on the nature of the fMRI task. The present study investigated both within-subject and group-level reliability of a combined three-task fMRI battery targeting three systems of wide applicability in clinical and cognitive neuroscience: an emotional (face matching), a motivational (monetary reward anticipation) and a cognitive (n-back working memory) task. A group of 25 young, healthy volunteers were scanned twice on a 3T MRI scanner with a mean test–retest interval of 14.6days. FMRI reliability was quantified using the intraclass correlation coefficient (ICC) applied at three different levels ranging from a global to a localized and fine spatial scale: (1) reliability of group-level activation maps over the whole brain and within targeted regions of interest (ROIs); (2) within-subject reliability of ROI-mean amplitudes and (3) within-subject reliability of individual voxels in the target ROIs. Results showed robust evoked activation of all three tasks in their respective target regions (emotional task=amygdala; motivational task=ventral striatum; cognitive task=right dorsolateral prefrontal cortex and parietal cortices) with high effect sizes (ES) of ROI-mean summary values (ES=1.11–1.44 for the faces task, 0.96–1.43 for the reward task, 0.83–2.58 for the n-back task). Reliability of group level activation was excellent for all three tasks with ICCs of 0.89–0.98 at the whole brain level and 0.66–0.97 within target ROIs. Within-subject reliability of ROI-mean amplitudes across sessions was fair to good for the reward task (ICCs=0.56–0.62) and, dependent on the particular ROI, also fair-to-good for the n-back task (ICCs=0.44–0.57) but lower for the faces task (ICC=−0.02–0.16). In conclusion, all three tasks are well suited to between-subject designs, including imaging genetics. When specific recommendations are followed, the n-back and reward task are also suited for within-subject designs, including pharmaco-fMRI. The present study provides task-specific fMRI reliability performance measures that will inform the optimal use, powering and design of fMRI studies using comparable tasks. [Copyright &y& Elsevier]

Abstract: In the social neuroscience of face processing, multiple roles are attributed to amygdala: signalling of fear/threat-stimuli, of emotional expression, and general salience. The current study aimed at a direct comparison of amygdala activation attributable to these conditions by contrasting amygdala responses to matched emotional (threatening and non-threatening) and of non-emotional salient faces in a visual search paradigm using cartoon faces. Participants (21 healthy volunteers) had to detect a target face (angry, happy, blue, red, differing in the exact same features) in an array of closely matched non-target faces. Behavioural results revealed a pop-out effect for all targets compared to non-targets, indicating that they were all salient, independently of being emotional or non-emotional. While significant amygdala activation was obtained for all trials with salient faces (compared to those containing only non-target faces), no significant differences in activation emerged between emotional threatening, emotional non-threatening, and non-emotional targets. Moreover, right and left amygdala activation for target trials was found correlated to the behavioural measure of target detection. These findings provide evidence for a general role of the amygdala in signalling salience in a visual search independent of modality. Given the critical involvement of the amygdala in several neuropsychiatric disorders, the current findings may contribute to further our understanding on dysfunctional neural circuits in these disorders. [ABSTRACT FROM AUTHOR]