The conclusion highlights three concepts that were not predicted by dream theorists. Firstly, dreaming and other states of consciousness are related to changes in the level of brain activation. Secondly, that, independent of activation, the brain opens and closes its gates of sensory input and motor output. The third and perhaps most significant conclusion is that the brain not only self-activates and isolates itself from the world, but it changes its chemical climate very radically. Two of the chemical systems necessary to waking consciousness are completely shut off when the brain self-activates in sleep. It is this difference in brain chemistry that probably determines the differences between waking and dreaming consciousness.