[Associative networks, formal thought disorders and schizophrenia. On the experimental psychopathology of speech-dependent thought processes].

Association psychology research in psychiatry dates back to Kraepelin, Aschaffenburg and C.G. Jung. Findings of the 1950s and 60s in this field suggest that semantic memory is organized in the form of a network. New results of experimental psychiatric studies indicate that schizophrenic symptoms, in particular formal thought disorders, are in part the result of an unfocussed activation or disinhibition of such associational network structures: The phenomenon of semantic priming is more pronounced in schizophrenic patients than in normals. Moreover, the phenomenon of indirect semantic priming on short stimulus onset asynchrony can be seen only in schizophrenic patients. The study of spontaneous speech further suggests the activation of structures responsible for the storage and processing of meaning. Increase in semantic priming, similar to that observed in schizophrenia, can further be observed in normal subjects on awakening from REM sleep. The findings are discussed in the framework of recent findings on the neurobiological causes of schizophrenia. They can be related structurally to an involvement of the frontal lobe, and functionally to disturbances of dopaminergic transmission. Methods such as the investigation of priming effects in lexical decision tasks, as well as concepts from the domain of cognitive neuroscience such as neural networks and the spreading activation model of lexical access, can help to bridge the gap between phenomenological psychopathology and neurobiology.