The present disclosure relates to a bioelectrical signal acquisition device, an interactive system, and related methods. The bioelectrical signal acquisition device includes a series of electrodes that are configured and positioned to effectively record bioelectrical signals from a user's head. The interactive system and related methods can be used to collect, display, and analyze the bioelectrical signals, especially signals related to sleep. The device, system, and methods can also be applied to modulate physiological or pathological conditions of the user.