In this video adapted from The Human Spark, Alan Alda continues his quest to discover what makes us human in a discussion with Dr. Todd Preuss on the subject of the brain and how it functions. Preuss studies the brain with the help of Magnetic Resonance Imaging or MRI machines. MRIs reveal the sophisticated circuitry of the brain’s cortex to explain how the cortex may differ in individuals and how those differences could relate to how people think or act.