Pathogenesis of Schizophrenic Delusions and Hallucinations: A Neural Model

• Published in: Schizophrenia bulletin 1996, Vol.22 (1), p.105-123
• Main Authors: Ruppin, Eytan, Reggia, James A., Horn, David
• Format: Article
• Language: English
• Subjects: Adult and adolescent clinical studies; Biological and medical sciences; Brain - physiopathology; Brain Mapping; Delusions; Delusions - diagnosis; Delusions - physiopathology; Delusions - psychology; Disease Course; Frontal Lobe; Frontal Lobe - physiopathology; Hallucinations; Hallucinations - diagnosis; Hallucinations - physiopathology; Hallucinations - psychology; Human; Humans; Medical sciences; Mental Recall - physiology; Models, Neurological; Nerve Degeneration - physiology; Nerve Net - physiopathology; Nerve Regeneration - physiology; Neural Networks; Neural Networks (Computer); Neural Pathways; Neural Pathways - physiopathology; Positive and Negative Symptoms; Psychiatric Status Rating Scales; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Psychoses; Schizophrenia; Schizophrenia - diagnosis; Schizophrenia - physiopathology; Schizophrenic Psychology; Synapses; Synapses - physiology; Temporal Lobe; Temporal Lobe - physiopathology
• ISSN: 0586-7614; 1745-1701
• DOI: 10.1093/schbul/22.1.105

We implement and study a computational model of Stevens' theory of the pathogenesis of schizophrenia. This theory hypothesizes that the onset of schizophrenia is associated with reactive synaptic regeneration in brain regions that receive degenerating temporal lobe projections. Concentrating on one such area, the frontal cortex, we model a frontal module as an associative memory neural network whose input synapses represent incoming temporal projections. Modeling Stevens' hypothesized pathological synaptic changes in this framework results in adverse side effects similar to hallucinations and delusions seen in schizophrenia: spontaneous, stimulus-independent retrieval of stored memories focused on just a few of the stored patterns. These could account for the delusions and hallucinations that occur in schizophrenia without any apparent external trigger and for their tendency to concentrate on a few central cognitive and perceptual themes. The model explains why the positive symptoms of schizophrenia tend to wane as the disease progresses, why delayed therapeutic intervention leads to a much slower response, and why delusions and hallucinations may persist for a long time when they do occur.