ABSTRACT/PROJECT SUMMARY Time does not heal all wounds equally. Approximately ten to twenty percent of people who havesuffered the death of a close loved one will develop a serious prolonged response to bereavement known ascomplicated grief in which griefs severity and duration continue to exert a substantially detrimental impact ondaily life many years even decades later. Older adults are at high risk for negative consequences of'complications' in the grief process that can accelerate age-related decline. By the age of 65 approximatelyone in four married adults in the United States will have faced the death of a spouse making complicated griefa serious public health concern for the aging population. To develop effective biobehavioral strategies forprevention and/or intervention it is imperative to better understand the nature and mechanisms of complicatedgrief. With the very recent inclusions of a provisional grief disorder in both the DSM-5 (in 2013) and the ICD-11(in June 2018) the field is currently grappling with the question of how to define disordered grief. Theprevailing hypothesis is that effective coping with bereavement requires a person to be able to flexibly shiftfocus between the tasks of processing the loss and restoring ones life. In contrast maladaptive spontaneousthought processes (i.e. yearning rumination) prevent the loss from being successfully integrated into ongoingdaily living. However the time scale at which these mental shifts take place and how they are enacted in thebrain is unknown and this limits our ability to effectively detect and intervene when older adults are showingsigns of complicated grief. Broadly the proposed study aims to test spontaneous thought dynamics and theirimplementation in large-scale brain networks as a mechanism of grief (mal)adaptation. Intrinsic brain networks(default mode salience frontoparietal control networks) function to limit or support the capacity for flexiblespontaneous thought and their function in grief may relate to how people think about and process the death ofa loved one. The proposed study will investigate the role of dynamic functional connectivity or time-varyinginteractions between large-scale brain networks using resting state fMRI data from widowed older adults withand without complicated grief representing a full range of grief symptom severity. In order to better characterizehow this brain activity might differ in complicated grief the proposed study also leverages data from anintranasal oxytocin manipulation to probe hypothesized motivation- and affect-driven influences. The proposedtraining will significantly advance the applicants progression towards an independent research career inclinical neuroscience through goals that emphasize research rigor and replicability (a current priority forpsychological science and neuroscience); advanced quantitative and neuroimaging skills; and knowledge ofcognitive-affective processes in psychopathology and aging. The fellowship will provide a foundation for theapplicant to catalyze a research program addressing mechanisms of adaptation to interpersonal stressors (likethe death of a partner) that can negatively influence older adults social cognitive and emotional functioning.