“The researchers also scanned the volunteers’ brains via fMRI and found that people doing the hardest memory tasks showed decreased activity in a brain area called the middle frontal gyrus, which earlier studies have shown is closely involved in decision-making. When you view this study in light of previous research, it seems the dynamic at play is a form of brain fatigue: Brain areas crucial to decision-making run low on energy and succumb to fatigue, not unlike muscles after a difficult workout.
The brain is an energy hog that uses 15 to 20 percent of the body’s circulating blood glucose each day. Particular brain areas use more or less of this energy depending on our neural workload. The latest study suggests that doing hard memory work requires a glut of energy and leaves less available for making good decisions. And when that happens, the cerebral gears start slipping and impulsiveness kicks in.”