Neurophysiological mechanisms of psychotic symptoms

Psychotic symptoms are supposed to be expression of highest order brain functions such as symbolic thinking, language, planning, empathy or complex emotional reactions. However, due to its historical roots, current psychiatric symptomatology is based on descriptions of disturbed behavior, which refer to metaphysic concepts rather than to brain function. Therefore, modern biological research suffers from an important gap between psychiatric semiology and contemporary knowledge in systems neurophysiology. The authors argue for a redefinition of psychiatric symptoms in a neurobiologically meaningful way. Based on recent empirical studies, this strategy is exemplified for auditory verbal hallucinations and formal thought disorder. In these examples, characteristic psychiatric symptoms can be related to circumscribed structural and functional alterations in the language system, allowing the description of clinical phenomena in terms of neurobiological events. This strategy is also applicable to other psychotic symptoms like emotional dysregulation and catatonia, where disturbances of the functional circuits of mood and motor regulation, respectively, are predicted. This approach to psychiatric symptoms is based on contemporary evidence concerning systems neurophysiology and is expected to provide meaningful and testable hypotheses for future research aimed to a better understanding of the pathogenesis of psychiatric disorders, to more accurate prognosis and to better targeted therapeutic strategies.