Facial expressions and complex IAPS pictures: Common and differential networks

Neuroimaging studies investigating emotion have commonly used two different visual stimulus formats, facial expressions of emotion or emotionally evocative scenes. However, it remains an important unanswered question whether or not these different stimulus formats entail the same processes. Facial expressions of emotion may elicit more emotion recognition/perception, and evocative pictures may elicit more direct experience of emotion. In spite of these differences, common areas of activation have been reported across different studies, but little work has investigated activations in response to the two stimulus formats in the same subjects. In this fMRI study, we compared BOLD activation patterns to facial expression of emotions and to complex emotional pictures from the International Affective Picture System (IAPS) to determine if these stimuli would activate similar or distinct brain regions. Healthy volunteers passively viewed blocks of expressive faces and IAPS pictures balanced for specific emotion (happy, sad, anger, fear, neutral), interleaved with blocks of fixation. Eye movement, reaction times, and off-line subjective ratings including discrete emotion, valence, and arousal were also recorded. Both faces and IAPS pictures activated similar structures, including the amygdala, posterior hippocampus, ventromedial prefrontal cortex, and visual cortex. In addition, expressive faces uniquely activated the superior temporal gyrus, insula, and anterior cingulate more than IAPS pictures, despite the faces being less arousing. For the most part, these regions were activated in response to all specific emotions; however, some regions responded only to a subset.