Neurology versus Psychiatry? Hallucinations, Delusions, and Confabulations.

Hallucinations, delusions, and confabulations are common symptoms between neurology and psychiatry. The neurological diseases manifesting with such symptoms (dementia, epilepsy, Korsakoff's disease, brain tumors, Parkinson's disease, migraine, right hemisphere stroke and others) would be the key to understand their biological mechanisms, while the cognitive sciences, neuropharmacology and functional neuroimaging would be the tools of such researches. It is possible to understand the perceptive rules of the mind and the mechanisms of the human consciousness based on these symptoms. However, hallucinations and delusions manifest with extraordinary vehemence with psychiatric disorders such as psychosis and schizophrenia, with which there is no evidence of brain lesions. Furthermore, they are subjective symptoms, and they do not have biological markers. Hence, they are prone to high inter-individual variability and depend on other variables (such as education, history of trauma), and are therefore difficult to reduce to unequivocal constructs. Causative mechanisms are probably multiple. For understanding these symptoms, a common framework between neurology and psychiatry is still missing. The psychopathology of French alienists over the 19th century, of S. Freud, and of Henry Ey over the 20th century gave way, in the second half of the 20th century, to the adoption of the DSM and neurosciences, to pursue a pure neurological perspective. However, although psychodynamic models seem nowadays (in a technological era) less influential, detailed clinical evaluations focusing on emotional-cognitive paradigms are probably the only way to lead to new neurobiological researches.