Brain imaging can predict how intelligent you are

As science has long suspected, overall brain size matters somewhat, accounting for about 6.7% of individual variation in intelligence. More recent research has pinpointed the brain’s prefrontal cortex, a region just behind the forehead, as a critical hub for high-level mental processing, with activity levels there predicting another 5% of variation in individual intelligence. Now, new research from Washington University in St. Louis suggests that another 10% of individual differences in intelligence can be explained by the strength of neural pathways connecting the left prefrontal cortex to the rest of the brain. The research shows that connectivity with a particular part of the prefrontal cortex can predict how intelligent someone is. The study is the first to provide compelling evidence that neural connections between the left prefrontal cortex and the rest of the brain make a unique and powerful contribution to the cognitive processing underlying human intelligence. This study suggests that part of what it means to be intelligent is having a prefrontal cortex that does its job well; and part of what that means is that it can effectively communicate with the rest of the brain. One possible explanation of the findings is that the prefrontal region is a “flexible hub” that uses its extensive brain-wide connectivity to monitor and influence other brain regions in a goal-directed manner. There is evidence that the left prefrontal cortex is the brain region that remembers or maintains the goals and instructions that help you keep doing what is needed when you’re working on a task. So it makes sense that having this region communicating effectively with other regions (the perceivers and doers of the brain) would help you to accomplish tasks intelligently. While other regions of the brain make their own special contribution to cognitive processing, it is the left prefrontal cortex that helps coordinate these processes and maintain focus on the task at hand, in much the same way that the conductor of a symphony monitors and tweaks the real-time performance of an orchestra. The researchers are suggesting that the left prefrontal cortex functions like a feedback control system that is used often in engineering, that it helps implement cognitive control (which supports fluid intelligence), and that it doesn’t do this alone. The findings are based on an analysis of functional magnetic resonance brain images captured as study participants rested passively and also when they were engaged in a series of mentally challenging tasks associated with fluid intelligence, such as indicating whether a currently displayed image was the same as one displayed three images ago. Previous findings relating left prefrontal cortex activity to challenging task performance were supported. Connectivity was then assessed while participants rested, and their performance on additional tests of fluid intelligence and cognitive control collected outside the brain scanner was associated with the estimated connectivity. Results indicate that levels of global brain connectivity with a part of left lateral prefrontal cortex serve as a strong predictor of both fluid intelligence and cognitive control abilities. Although much remains to be learned about how these neural connections contribute to fluid intelligence, new models of brain function suggested by this research could have important implications for the future understanding — and perhaps augmentation — of human intelligence. The findings also may offer new avenues for understanding how breakdowns in global brain connectivity contribute to the profound cognitive control deficits seen in schizophrenia and other mental illnesses.