A social dimension of emotion: Functional neuroanatomy and individual differences

Sociality and individual differences may play an important role in emotional processing. Using behavioral and functional magnetic resonance imaging (fMRI) experiments, this dissertation aims (1) to characterize the behavioral and neural activation patterns associated with processing emotional stimuli that vary on a dimension of sociality; (2) to determine the modulatory effects of personality factors in emotion processing. Activations in response to facial expressions and IAPS pictures were compared to determine if faces, an inherently social feature, would activate a distinct emotional pattern. Both stimuli activated amygdala, hippocampus, ventromedial prefrontal cortex, and visual cortex. In addition, facial expressions preferentially activated the superior temporal gyrus, anterior insula and anterior cingulate, even though subjective reports of valence and arousal were lower for facial expressions compared to IAPS pictures. In another set of experiments, a novel paradigm was developed using film and picture segments to induce and maintain social, joy/amusement and sadness, and nonsocial emotions, appetite and disgust. In the behavioral experiment, psychophysiological and subjective responses suggested that sociality influenced emotional responses to valence, validating the paradigm for the neuroimaging study. The neuroimaging results suggest sociality may be as neurobiologically meaningful as valence in determining the neural activation pattern of emotion. Social emotions activated sublenticular extended amygdala, superior temporal gyrus, hippocampus and posterior cingulate. Finally, personality traits with relevance to emotional and social processing (neuroticism, extraversion and alexithymia) were correlated with activation patterns to determine the influence of these factors in processing emotional stimuli. Neuroticism correlated with dmPFC activation in response to positive stimuli. Extraversion inversely correlated with anterior insula activation in response to negative stimuli. Alexithymia correlated with posterior insula activation in response to positive and negative films. These results extend previous findings by demonstrating facial expressions and social films preferentially activate regions that process the social dimension of emotion compared to other emotional eliciting stimuli (IAPS pictures and nonsocial films, respectively). Overall, these results suggest sociality and individual variation is meaningful in eliciting neural activation response to emotional stimuli. Investigating the interaction between emotion, sociality and personality factors will advance our understanding of emotion and disorders involving both social and emotional dysfunction.