Dynamic causal modeling of the prefrontal-amygdala network during processing of emotional faces.

INTRODUCTION The importance of the amygdala - medial orbitofrontal cortex (OFC) network during processing of emotional stimuli, emotional faces in particular, is well established. This premise is supported by converging evidence from animal models, human neuroanatomical results, and neuroimaging studies. However, there is missing evidence from human brain connectivity studies that the OFC and no other prefrontal brain areas such as the DLPFC or VLPFC are responsible for amygdala regulation in the functional context of emotional face stimuli. METHODS Dynamic causal modeling of ultra-high field functional MRI data acquired at 7 Tesla in 38 healthy subjects and a well-established paradigm for emotional face processing were used to assess the central role of the OFC in order to provide empirical validation for the assumed network architecture. RESULTS Using Bayesian model selection, it is demonstrated that indeed the OFC, and not the VLPFC and the DLPFC, down regulates amygdala activation during the emotion discrimination task. Additionally, Bayesian model averaging group results were rigorously tested using bootstrapping, further corroborating these findings and providing an estimator for robustness and optimal sample sizes. DISCUSSION While it is true that VLPFC and DLPFC are relevant for the processing of emotional faces and are connected to the OFC, the OFC appears to be a central hub for prefrontal-amygdala interaction.