Human amygdala is activated by social and emotional information

It has been a widely held view in cognitive neuroscience that the human amygdala is primarily involved in fast processing of stimuli that elicit fear. Recent studies have, however, suggested a broader role for the amygdala, for instance, sensitivity to stimulus relevance, such as emotionally and socially significant information. Careful experimental test of how these factors modulate amygdala responsiveness has not been carried out previously.

In their recent study, Dr. Pascal Vrticka et al. (2013) studied with a two-by-two factorial design the sensitivity of amygdala to emotional valence (i.e., positive vs. negative) vs. social (i.e., social vs. non-social) information contained in pictorial stimuli. Specifically, 19 healthy female volunteers were presented 240 pictures taken from the International Affective Pictures collection during functional magnetic resonance imaging. In the first condition, emotionally neutral pictures with social vs. non-social content were presented to the subjects with a task to rate the photographic quality of the pictures, serving as a non-emotional baseline. In three other viewing conditions, emotional images were presented with three types of tasks across which the analysis was finally collapsed.

The results indicate that the human amygdala does respond to social information more robustly than to non-social information also in case of neutral stimuli. Further, there was an overall effect towards higher sensitivity to negative as compared to positive images, and this valence effect was largely driven by increased responsiveness to negative information in non-social scenes. This suggests that social stimuli need not be negative in order to be processed by amygdala as behaviorally relevant.

This valence vs. social information interaction was further pronounced in the right amygdala and was modulated by trait anxiety measures of the subjects. Similar valence vs. social information interactions were noted in the right fusiform gyrus, right anterior superior temporal sulcus, and medial orbitofrontal cortex, suggesting that these areas form a network that detects stimulus relevance in humans.  Overall, these results significantly advance knowledge of the role of amygdala in processing of social and emotional aspects of pictorial stimuli, and how the amygdala activation is modulated by personality of the experimental subjects.

Reference: Vrticka P, Sander D, Vuilleumier P. Lateralized interactive social content and valence processing within the human amygdala. Frontiers in Human Neuroscience (2013) 6:358. http://dx.doi.org/10.3389/fnhum.2012.00358