The overall goal of the DISCOVERY study is to better understand what factors contribute to changes in cognitive (i.e., thinking and memory) abilities in patients who experienced a stroke. The purpose of the study is to help doctors identify patients at risk for dementia (decline in memory, thinking and other mental abilities that significantly affects daily functioning) after their stroke so that future treatments may be developed to improve outcomes in stroke patients. For this study, a stroke is defined as either (1) an acute ischemic stroke (AIS, or blood clot in the brain), (2) an intracerebral hemorrhage (ICH, or bleeding in the brain), (3) or an aneurysmal subarachnoid hemorrhage (aSAH, or bleeding around the brain caused by an abnormal bulge in a blood vessel that bursts). The investigators hypothesize that: 1. The size, type and location of the stroke play an important role in recovery of thinking and memory abilities after stroke, and pre-existing indicators of brain health further determine the extent of this recovery. 2. Specific stroke events occurring in individuals with underlying genetic or biological risk factors can cause further declines in brain heath, leading to changes in thinking and memory abilities after stroke. 3. Studying thinking and memory alongside brain imaging and blood samples in patients who have had a stroke allows for earlier identification of declining brain health and development of individualized treatment plans to improve patient outcomes in the future.