Not totally sure but from what i remember from my college days a large part of the brain stimulated by LSD! Opens alot of your mind that maybe should be left alone!!
I presume you're referring to all types of hallucination.<br />
The Occipital lobe is merely the visual processing center.<br />
The temporal lobe is what you're looking for.
Visual function is mostly associated with the occipital lobe of the brain, which is located in the back, bottom part of the skull.