At parties and social gatherings, I usually go for the one to one conversations. Extroverts having a talk-fest drain me. I recall attending a meeting of Community Visitors, (advocates for disabled in state accommodation) and the noise was deafening; I was the only introvert in sight. Think of being in a room where 300 loud conversations were taking place. All the Community Visitors were extroverts; it was their job to interact and that vigorously with the disabled and get their responses.
Where I am with big, big, crowds and have to intereract for long periods of time with a lot of people I begin to fade and have to duck out and be alone for five or ten minutes every two or three hours. If I can't do that, then I need to withdraw and conserve energy. By the end of the day I will have a headache, and be totally drained of energy internally and just plain tired. I will be talking goobledy-gook by then. Brain not functioning.