system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens in the brain when someone has a "lightbulb moment" where they suddenly understood a math concept or other concept? Did a physical change in their brain occur during this "lightbulb moment"?

 When you learn something new what actually happens in your brain? Is it like a new neuron grows in a certain part of the brain, or links to a different neuron? or is it something else?

What about if learning something physical, does that mean the same changes happen in a different region of the brain like the cerebellum?
gpt
Until a "light bulb moment" occurring is captured in an MRI or similar scan at the moment of it's occurrence, and that is done many times with many different people to truly capture sufficient reliable and consistent data, nobody can give you a proper answer on what "happens" to / in the brain.

If anybody does give you an answer, while this observed data does not yet exist, know that it is speculation, even if given by the world's best neuroscientist.

That being said - the brain is known to process information not only consciously, but subconsciously as well. Namely, it is known to perform problem solving tasks in this manner. It's called Unconscious Cognition.

Sudden realization moments happen likely because your brain has been working on a problem for a while, while you were unaware of it, and has either reached a solution which you then become aware of, or you have acquired some additional information that it required in order to reach that solution.

Minor Addendum: *Your brain does a LOT that you are not aware of. Imagine being aware of every single aspect of every single sensory input being processed, being aware of all memory alterations or fading, being aware of all the cognitive functions involved in forming sentences or interpreting language spoken to you, being aware of all the cognitive functions involved in you reaching to grab a can of soda with your hand (the distance to reach, the amount of pressure to get a good grip, the amount of muscle tension to control the speed of your reach, even the recognition of all the visual patterns that make up the "soda can" object), etc. Your brain does a whole lot of work subconsciously, and a lot of problem solving already in most aspects of life. The same applies to cognitive efforts like solving mathematical problems, or other such endeavors.*