Re: What are hallucinations caused by?

Hallucinations are caused by abnormal chemical reactions in the brain. The occipital lobe, which is located in the back of the brain, is associated with visual experiences. When the eye is struck by light of some kind, it sends electric signals to the occipital lobe. Once the occipital lobe is activated by these signals, the corresponding visual experience becomes conscious. But the signal is not entirely electrical all the way through. The fibers that connect the eyes to the occipital lobe have tiny microscopic gaps between them and the occipital lobe, and these gaps are called synaptic gaps. Once the signal reaches the end of the fibers, chemicals are released and they travel across the gap, and when they make contact with the occipital lobe, that's when the occipital lobe becomes active.

However, there are certain situations in which foreign chemicals enter the gap, thereby causing unexpected activation of the occipital lobe. When this happen, the visual experience that follows is a hallucination. For example, when taking drugs, you ingest chemicals that can enter the synaptic gaps and activate the occipital lobe even though the eyes have not sent signals to the brain. Another situation is when one has a psychotic disorder of some kind (psychotic means having hallucinations or delusions). In these cases, either the body itself (sometime even the brain) produce chemicals abnormally that have the effect of activating the occipital lobe, or the optic fibers produce the normal chemicals that cause vision but at abnormal times and for abnormal reasons (the result is that it seems spontaneous).

And of course, "hallucination" is a term that is not only reserved for vision. People can have auditory hallucination or hallucinations of any one of the other three senses. Auditory experiences are associated with the temporal lobes (lower left and right sides of the brain), tactile experiences are associated with the parietal lobe (at the very top of the brain), and taste and smell are associated the areas deep in the middle of the brain. For any one of these brain areas, chemicals of certain types can enter into the synaptic gaps and cause unexpected activation of the brain, thereby giving rise to hallucinations.

Hope that answers your question.
Gibran