Background: Abnormalities in amygdala function have been implicated in major depression. However, results are inconsistent, and little is known about how the depressed brain encodes conflicting social signals. We sought to determine how the task relevance of socio-emotional cues impacts neural encoding of emotion in depression.
Methods: Eighteen medication-free depressed patients and 18 matched controls participated in an FMRI experiment. Whole-brain analyses and a region-of-interest approach was used to measure amygdala activity during the presentation of fearful, happy, or neutral target faces with congruent, incongruent, or neutral distracters.
Results: Greater amygdala activity to target fearful faces was associated with depression, as was attenuated amygdala activity to target and peripheral happy faces. Although no group differences emerged in the amygdala to unattended fearful faces, we observed reduced ventrolateral and dorsomedial prefrontal activity in depressed individuals during this condition.
Limitations: Nine patients had a history of anti-depressant use, though they were unmedicated for at least three months at testing.
Conclusions: Depression was associated with reduced amygdala reactivity to positive social stimuli. However, enhanced amygdala responsiveness to negative emotional cues was only observed to target (attended) expressions. The results highlight the need to further determine factors that affect emotional reactivity in depression.
Keywords: Amygdala; Attention; Emotion; Facial expressions; Fmri; Major depression.
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