system
Given the following post, respond as if you're commenting on Reddit:
human
Does our brain use more calories if we are actively doing something mentally stimulating?

If our brains use around 20% of our calories, is this a general flat rate the brain just uses, or if we're doing something like learning or problem solving does it require more calories?
gpt
The brain is metabolically active just like all other tissues. When it is doing more, it requires more - glucose, blood flow, oxygen, etc. We can actually watch specific areas of the brain light up on functional MRI scans when a person is performing specific tasks. The fMRI works precisely because active areas of the brain will begin consuming more nutrients when they are being stimulated.