<prompt> Answer this question truthfullyWhat is a transient ischemic attack TIA and how is it characterized in terms of regional cerebral ischemia and duration of focal neurologic deficits?  <response>: <reason> A transient ischemic attack TIA is a type of regional cerebral ischemia that results in focal neurologic deficits lasting less than 24 hours, with the majority of cases resolving in less than 15 minutes. 