Magnetic Resonance Imaging (MRI) Scans allow us to map the maturation of the brain. This slide illustrates brain development through early adulthood, with blue indicating the mature state. The prefrontal cortex (white circles), which governs judgment and decision-making functions, is the last part of the brain to develop. This may help explain why teens are prone to risk-taking, are particularly vulnerable to drug abuse, and why exposure to drugs at this critical time may affect propensity for future addiction.