When you're mentally exhausted, your brain might be doing more behind the scenes than you think. In a new study using functional MRI, researchers uncovered two key brain regions that activate when people feel cognitively fatigued—regions that appear to weigh the cost of continuing mental effort versus giving up. Surprisingly, participants needed high financial incentives to push through challenging memory tasks, hinting that motivation can override mental fatigue. These insights may pave the way to treating brain fog in disorders like PTSD and depression using brain imaging and behavior-based therapies.