Facial emotion processing in major depression: a systematic review of neuroimaging findings

A Medline search was performed up to August 2011 in order to identify studies on emotional face processing in acutely depressed patients compared with HCs. A total of 25 studies using functional magnetic resonance imaging were reviewed.The analysis of neural activation data showed abnormalities in MDD patients in a common face processing network, pointing to mood-congruent processing bias (hyperactivation to negative and hypoactivation to positive stimuli) particularly in the amygdala, insula, parahippocampal gyrus, fusiform face area, and putamen. Furthermore, abnormal activation patterns were repeatedly found in parts of the cingulate gyrus and the orbitofrontal cortex, which are extended by investigations implementing functional connectivity analysis. However, despite several converging findings, some inconsistencies are observed, particularly in prefrontal areas, probably caused by heterogeneities in paradigms and patient samples.Further studies in remitted patients and high-risk samples are required to discern whether the described abnormalities represent state or trait characteristics of depression.Major depression ranks among the most debilitating diseases worldwide and is estimated to produce the second largest disease burden by the year 2020 [1]. Despite an increasing amount of empirical studies investigating abnormalities in affective processing in unipolar depression, understanding the neurobiological underpinnings is still a major research goal and is essential for novel treatment developments. In a large body of behavioral studies, depression has been characterized by mood congruent emotion processing biases in different aspects of cognition [2-5]. Apparently, these cognitive biases have been reported to be particularly prominent for emotional faces. Depressed patients seem to be less sensitive in the identification of emotional faces and, in addition, a negative response bias was found: they tend to interpret neutral faces as sad and happy faces as neu