1. A brain-machine interface for extracting user action intentions while navigating a continuous three-dimensional asynchronous interactive environment, the interface comprising: one or more processors and a memory, the memory having instructions encoded thereon such that upon execution of the instructions, the one or more processors perform operations of: processing brain activity of a user engaged in navigating a three-dimensional video environment, wherein the user navigates the three-dimensional video environment while simultaneously being monitored; generating subliminal stimuli for presentation to a user; modifying the user's perceived experience while navigating the continuous three-dimensional asynchronous interactive environment through presentation of the subliminal stimuli when the user is required to make a decision regarding an action to be performed by the user in the continuous three-dimensional asynchronous interactive environment, wherein the subliminal stimuli are presented at predetermined time points; assessing the user's brain activity during presentation of the subliminal stimuli to relate the user's brain activity to the modification of the user's perceived experience at the predetermined time points; and classifying the user as having at least one brain state in a set of brain states by interpreting the user's brain activity in relation to the subliminal stimuli presented at the predetermined time points to determine whether the action is an action intended by the user, wherein the set of brains states comprises an intention to go state, an intention to stop state, and a no intention state.