Role of the amygdala in processing threatening animals and manipulable objects

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DESCRIPTION (provided by applicant): Excessively increased or decreased fear is strongly associated with a number of brain disorders, including social and animal phobias, posttraumatic stress disorder, autism spectrum disorder, and William's syndrome. The amygdala is confirmed to play an important role in emotional processing, particularly for negative/threatening stimuli. Recent studies have also shown that the amygdala is responsive to social stimuli, including neutral faces and visual social information. However, the stimuli used in most of these studies contain human or human-related information, which indicates that the amygdala is sensitive to animate, conspecific information. Little is known about whether the amygdala plays a more general role in processing any animate entities, and further, what the common role of the amygdala is in different varieties of brain disorders. Our long-term goal is to determine neural mechanisms of fear to different categories of stimuli. The objective of this proposal is to determine how the amygdala participates in processing different categories of threatening stimuli; i.e., threatening animals and manipulable objects. The central hypothesis for the proposed research is that the amygdala activity is highly associated with detecting animate entities (i.e., living things that move on their own). Our rationale for the proposed research is that determination of the relationship between stimulus category and amygdala activation would shed light on neural mechanisms of fear and emotional-related brain disorders. We plan to test our central hypothesis and accomplish the overall objective of this application by pursuing three specific aims, to determine the effects of (1) modality; (2) animate and social context; and (3) conscious awareness on amygdala activation for threatening animals and objects. A series of studies will be conducted, mainly using functional magnetic resonance imaging (fMRI) technique, with native Chinese speakers as subjects. In order to equate affective levels across categories, valence and arousal levels will be rated and matched before fMRI scanning in separate groups of subjects. This proposed research is significant, because it will not only elucidate the category representation in the amygdala, but also help us understand the nature of emotional-related brain disorders, and contribute to an improvement on rehabilitative efforts for patients with such disorders. PUBLIC HEALTH RELEVANCE: The proposed research is highly relevant to public health. It will help us understand the nature of emotional-related brain disorders, and contribute to an improvement in rehabilitative efforts for patients with such disorders. There is also a significant positive impact in understanding how the amygdala is prepared in an evolutionary manner when people are afraid of different categories of threatening stimuli.