Activation Network Localization of Facial Emotion Processing

Facial emotion processing is a basic psychological function of the human brain. Functional neuroimaging techniques have been widely used to probe its neural substrates in healthy subjects. However, like many other psychological functions, functional activations during facial emotion processing have been reported throughout the brain, and the findings are largely inconsistent across studies. Here, we attempted to test whether heterogeneous functional neuroimaging findings of facial emotion processing localized to a connected network and whether network localization could partly explain the poor reproducibility observed. First, using the activation likelihood estimation (ALE) meta-analysis technique, we showed that individual-brain-based reproducibility was low across studies. Then, using a new technique termed ‘activation network mapping’, which was adapted from lesion network mapping, we found that network-based reproducibility across these same studies was rather high; also, these seemingly heterogeneous functional neuroimaging findings mainly localized to a common brain network. Finally, our localized network based on activation matched brain stimulation locations—and the network derived from it—that disrupted facial emotion processing. It also aligned well with structural abnormalities in alexithymia—a disorder characterized by a deficiency in the ability to identify emotions, and brain lesions that disrupt facial emotion processing. Our results suggest that heterogeneous functional neuroimaging findings of facial emotion processing in healthy people localize to a common connected network, which improves the seemingly poor reproducibility among functional neuroimaging studies. Activation network mapping may prove to be a novel network-based technique that is potentially broadly applicable to localize brain networks of cognitive functions based on brain activations in healthy individuals.