The broad goal of this project is to determine how emotional memories modify social perception. The precise evaluation of social signals, such as facial expressions, is the results of life-long learning and refinement but also requires the integration of recent social encounters and their emotional content. The central hypothesis of this proposal is that the process of integration between remote and recent socioemotional memories changes with age and this change is manifested in the amygdala, a central component of the brain circuit involved in emotion and social behavior. The amygdala has been implicated in the decline of social cognition in the elderly, particularly with regard to facial emotion perception. We will determine how emotional facial expressions are represented in the young and old amygdala, and how these representations are modified by recent or remote social experience. Nearly half of the visual neurons in the young amygdala selectively respond to facial expression and or facial identity. The global activity is larger for aggressive faces compared to neutral and appeasing expressions. An age-related shift in emphasis in favor of positive emotions and a deficit in recognizing threatening faces predicts a different pattern of response in the aging amygdala. We will first characterize neural ensemble response while subjects are viewing static images of 30 unfamiliar individuals displaying aggressive, neutral and appeasing facial expressions. The subjects are then exposed (once for the short-term memory study and repeated times for the long-term memory study) to video clips about each of the 30 test individuals behaving in a particular emotional state - aggressive, neutral, or appeasing - thereby conditioning the subject to associate each test individual with that emotional style. We then present to the subject the three static images of each test individual again, and response patterns pre- and post-video training will be compared to evaluate the effect of social experience in both young and old subjects.
Emotional and social cognition are intimately linked to mental health. The amygdala serves as a 'gate' for human emotional behavior by virtue of its connections to both brain areas that serve higher mental functions and centers that control cardiovascular and immune responses. Abnormal activity in the amygdale has been found in the majority of psychiatric diseases, particularly in anxiety and mood disorders, but also in age-related neurodegerative diseases. Understanding its normal function and changes between the young and old amygdala will be a critical step toward finding effective treatments for these diseases. ? ? ?
