Systems theory, in this context, may be regarded as an extension of Braid's original conceptualization of hypnosis[89][page needed] as involving a process of enhancing or depressing nervous system activity. Systems theory considers the nervous system's organization into interacting subsystems. Hypnotic phenomena thus involve not only increased or decreased activity of particular subsystems, but also their interaction. A central phenomenon in this regard is that of feedback loops, which suggest a mechanism for creating hypnotic phenomena.[90][91] Source Wikipedia