'Concert brain' is something that occurs any time between a day before a concert to the day after a concert. It Involves songs by the performer(s) being stuck in your head and/or wanting to dance or imitate the dance moves performed by the performer(s). Effects may vary from person to person.
Friend: "That Imagine Dragons concert yesterday was amazing"
Friend2: "Yeah! I haven't stopped listening to their CD! I think I still have Concert Brain"