Dr. Hobson has constructed a model of dreaming to help us understand various states of consciousness. The AIM model is based on the interplay between three crucial brain attributes of consciousness: arousal-activation, source of information (excitation by real-world events versus brain-generated messages), and modulation (changes induced by cholinergic or serotonergic and noradrenergic transmitters). Normal, drug-induced, and pathological states can all be placed in the space created by these three dimensions, thus demonstrating their affinity. One can intentionally alter states of consciousness by manipulating any one of the three dimensions. For example, one can change the source of excitation as in hypnosis, trance, relaxation, and meditation or one can affect the chemical balance by ingesting psychedelics, hypnotics, stimulants, or other mood-altering drugs.