Laterality effect on emotional faces processing: ALE meta-analysis of evidence.

Recognizing emotion from facial expressions draws on diverse psychological processes implemented in a large array of neural structures. Two major theories of cerebral lateralization of emotional perception have been proposed: (i) the Right-Hemisphere Hypothesis (RHH) and (ii) the Valence-Specific Hypothesis (VSH). To test these lateralization models we conducted a large voxel-based meta-analysis of current functional magnetic resonance imaging (fMRI) studies employing emotional faces paradigms in healthy volunteers. Two independent researchers conducted separate comprehensive PUBMED (1990-May 2008) searches to find all functional magnetic resonance imaging studies using a variant of the emotional faces paradigm in healthy subjects. Out of the 551 originally identified studies, 105 studies met inclusion criteria. The overall database consisted of 1785 brain coordinates which yield an overall sample of 1600 healthy subjects. We found no support for the hypothesis of overall right-lateralization of emotional processing. Conversely, across all emotional conditions the parahippocampal gyrus and amygdala, fusiform gyrus, lingual gyrus, precuneus, inferior and middle occipital gyrus, posterior cingulated, middle temporal gyrus, inferior frontal and superior frontal gyri were activated bilaterally (p=0.001). There was a valence-specific lateralization of brain response during negative emotions processing in the left amygdala (p=0.001). Significant interactions between the approach and avoidance dimensions and prefrontal response were observed (p=0.001).