Hallucinations are defined as sensations produced by the brain but without any external stimulus. They can be related to the sensation of being touched by a stranger, hearing someone walking around the room, knocking on the door or window, or calling our name.

They occur when we are awake and it is not true that they indicate a neurological disease or a brain disorder. Research is still ongoing to explain how hallucinations occur and what is responsible for them. One hypothesis is that it may be closely related to the appearance of delta waves in the cerebral cortex. It has also been pointed out that hallucinations are emotional in nature however, scientists have not been able to explain why.

The hallucination research aims to show which networks of neurons in our brain are responsible for specific concepts, e.g. a table, a lamp, a dog or food, and also to show whether our emotional attitude towards them influences the appearance of hallucinations involving them.