system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does ADHD affect the brain?
gpt
You know the story of the ant and the grasshopper? The ant works hard, plans for the future, prepares and stores food for winter. Grasshopper fucks around all summer, procrastinates, does whatever he wants and when winter comes he's caught off guard and underprepared. 

Well, in the brain of an ADHD person, the ant is having a nap and the grasshopper is running the show. They have difficulty with executive function (future planning, seeing how decisions will impact them later, foreseeing consequences, benefits of delayed gratification and things of this nature.) Basically the part of the brain that tells you "that's a bad idea" or "you shouldn't do that" or "you should be doing..." is under active. This is why stimulants are used to treat ADHD.  They give the ant part of the brain a jolt and help him rein in the grasshopper.