A hallucination is when someone sees or hears something that isn't really there. It's like having an illusion or a false perception of something that seems real to the person experiencing it, but it's actually just in their mind. Full definition
12:15 Functional neuroimaging: promises and challenges — unravelling the neuroscience of auditory hallucinations in schizophrenia Kenneth Hugdahl, Professor, Department of Biological and Medical Psychology, University of Bergen Short introduction by Cecilie Morland, PhD student, UiO (cmbn.no)
There are also a few cameos from Nick's friends — Ray Winstone (who starred in the video for «Jubilee Street»), Kylie Minogue and Blixa Bargeld (longtime guitarist for the Bad Seeds) explaining why he left the group in 2003 after 20 years with the band — who appear as hallucinations in the passenger seat of his car, rather than through a standard interview segment. (indiewire.com)
They also spent more time in a state characterized by excessive communication in visual regions of the brain, which could be the basis for visual hallucinations experienced in psychosis. (sciencedaily.com)