Introverts and extroverts have differences in their brains

Well I'm a introvert

Im a extrovert at heart but an introvert in body :P

I can confirm this to be true.

I guess ambiverts have a little of both?

I was an extrovert once

Although now it's inaccurate to classify someone as an 'introvert' or 'extravert'. It's measured by levels of the extroversion trait, coz people are complex :)