Since the beginning of this project we have screened over 3000 subjects for this study. We have enrolled approximately 202 youth with bipolar disorder (BD), 295 subjects at risk for BD because they have a parent or sibling with the illness, and 109 adults with BD. This year, approximately 35 new subjects were enrolled. This year we continued our work designed to identify the brain mechanisms underlying BD in children; compare brain function in youth and adults with BD in order to begin to understand how the illness develops over time; and compare brain function in youth at familial risk for BD to those with BD and those at low risk, in order to facilitate the eventual development of preventive interventions. Regarding our work on the brain mechanisms mediating BD, much of that work consists of, not only comparing youth with BD to healthy youth, but also comparing youth with BD to those with severe, chronic irritability (the so-called Disruptive Mood Dysregulation, or DMDD, population, see Annual Intramural Research Report ZIAMH002786). It is important to compare youth with BD and those with DMDD because the latter frequently receive the diagnosis of BD in the community, despite not having a history of manic episodes. This potential misdiagnosis is important from a therapeutic and public health perspective. That is, compared to severe, chronic irritability, BD in youth is treated with medications with high side-effect burden. Therefore, it is important to identify accurately youth with BD and not extend the boundaries of the diagnosis inappropriately. This year we completed a study in which we compared brain activity in youth with BD vs. those with DMDD during a task that involved subjects labeling face emotions. The results of that study are described under ZIAMH002786. In addition to using task-based paradigms to compare the groups, we also compared BD, DMDD, and healthy youth using resting state imaging techniques. Such techniques are designed to study brain function while subjects are resting and thus to identify intrinsic functional connectivity amongst brain regions. This year we published work specifically focused on connectivity between subnuclei of the amygdala, an important brain region for emotional processing, and the rest of the brain in BD, DMDD, and healthy youth. We found hyperconnectivity in BD between the left basolateral amygdala, a region specifically involved in fear conditioning, and both the medial aspect of the frontal pole and the posterior cingulate/precuneus. The latter two regions are important in social-emotional processing and cognitive flexibility, two processes that are deficient in youth with BD. Currently, we are analyzing data from a resting state study that includes both youth and adults with BD and that uses an analytic approach that examines connectivity amongst all regions in the brain. While we did not find developmental differences in connectivity between adults and youth with BD, both patient groups differed from healthy subjects in intrinsic connectivity within and between cortico-striatal and temporal-parietal networks. These networks mediate attention, cognitive control, and response processing, processes that are known to be impaired in BD. Another major focus of our work on this project this year involves children who are at risk for BD because they have a parent or sibling with the illness. A unique aspect of this work has been that our work with at risk children extends down to the preschool years. In one study, we demonstrated that high-risk preschoolers demonstrated significantly more intense, pervasive, and clinically concerning problems in anger modulation and behavior dysregulation on a standardized assessment task, compared to youth at low-risk for BD. This suggests the importance of studying and monitoring at-risk children from an early age. We also studied intra-subject variability in response time (ISVRT) in healthy preschoolers at familial risk for bipolar disorder. Increased ISVRT is thought to represent attentional lapses, and increased ISVRT has been identified in school-aged youth at risk for BD. Using a developmentally appropriate computerized task, we found that preschoolers at risk for BD, like older at-risk children, have evidence of attentional lapses, again highlighting the importance of early assessment and follow-up. We are currently analyzing data from a sample of school-aged at risk, BD, and healthy youth that uses a neuroimaging task specifically designed to identify the brain regions mediating increased ISVRT in youth with, or at risk for, BD. Of note, we also completed the development of a neuropsychological testing battery that will allow us to determine whether Amish children at risk for BD have cognitive deficits similar to those seen in non-Amish children. If so, work in this extended pedigree, genetically isolated population could help to elucidate some of the genetic mechanisms mediating these cognitive deficits. In addition to the work described above, we are currently gathering functional neuroimaging data on school-aged children at risk for BD on several face emotion processing tasks. Of note, youth and adults with BD, as well as youth at risk for the illness, have deficits identifying face emotions. Specifically, we are using an implicit face emotion processing (i.e., gender identification) task and a task in which subjects are asked to label face emotions. In the implicit face emotion processing task, we assessed neural response to face-emotion stimuli with different intensities of happy, angry, and fearful expressions during fMRI in a sample of adolescents with BD, their first degree relatives, and healthy youth. Neural activity to faces differed among the three groups by emotion and intensity in a number of regions, including the ventrolateral prefrontal cortex (VLPFC). Preliminary post hoc analyses of neural activity in the VLPFC revealed age-related abnormalities in the at risk sample. There are two important aspects to these findings. First, dysfunction in VLPFC, an important region in mediating between emotional and attentional circuits, has been implicated in other studies of youth at risk for BD. Second, the age-related finding, if confirmed in more detailed analyses, might indicate that the at-risk population can be differentiated between older, resilient youth, who have passed through much of the age of risk for BD without developing illness, and younger youth who are still at more significant risk. The second paradigm, which involved face emotion labeling, also showed dysfunction in youth at risk in the VLPFC, as well as in other areas of the prefrontal cortex. This finding was due to the fact that youth at risk for BD have hyperactivity in these prefrontal regions when viewing intensely happy faces. Prior research has suggested an association between reactivity to happy faces and BD, which investigators have speculated is related to the abnormal degree of positive affect (i.e., euphoria) characteristic of manic episodes.