[An imbalance between drive and guidance. A new model for the pathogenesis of schizophrenia]. / Een disbalans tussen kracht en sturing. Een nieuw model voor de pathogenese van schizofrenie.

BACKGROUND: We still do not know how genetic and environmental factors cause schizophrenia. The pathogenesis of this illness is unknown. AIM: To develop a pathogenetic model that has greater explanatory power than the existing hypotheses concerning schizophrenia. METHOD: We searched the literature with the help of Medline (from 1966) using the search terms 'schizophrenia', 'basal ganglia', 'striatum' and 'cerebellum'. We also consulted recent manuals on schizophrenia, evolutionary psychiatry and neuroanatomy. RESULTS: The analysis showed that during the phylogenesis and ontogenesis of the brain two mechanisms, which are primarily motor-control mechanisms, are applied to the intentional level of functioning; one of these initiates and delivers power to intentions (the drive mechanism), whereas the other steers and guides intentions (the guidance mechanism). As a result of the repeated application of these two mechanisms an imbalance to the detriment of the drive mechanism in the end manifests itself as schizophrenia. The model clarifies the clinical and epidemiological findings and the course of the illness. CONCLUSION: The model provides a more comprehensive explanation for existing clinical and epidemiological data than do current alternatives. The model is compliable with the main prevailing views of psychiatrists on schizophrenia and it places the genesis of schizophrenia in an evolutionary perspective.

[Psychomotor retardation in depression assessed by visuomotor tasks. Overview and achievements of ten years' research]. / Psychomotorische vertraging bij depressie, gemeten met visuomotorische taken. Overzicht en plaatsbepaling van tien jaar onderzoek.

BACKGROUND: A new line of research into psychomotor retardation in patients with a major depressive disorder began about ten years ago. The purpose of the research was twofold: to obtain a clearer understanding of psychomotor retardation in patients with a major depressive disorder and to assess the importance of psychomotor retardation for the diagnosis and treatment. AIM: To present an overview of the results of these studies in which psychomotor retardation of these patients was investigated. METHOD: The patients had to perform visuomotor tasks involving pen movements. The psychomotor retardation was measured by recording their pen movements objectively and accurately by means of a computer and digitiser. RESULTS: Patients with major depressive disorder showed pronounced psychomotor retardation in the visuomotor tasks. The psychomotor retardation appeared to be of both a cognitive and motor nature. The treatment study which examined the effect of fluoxetine on psychomotor retardation revealed that the cognitive retardation disappeared but the motor retardation remained. It was particularly the more retarded patient who responded well to fluoxetine. The research that compared the psychomotor retardation in various subtypes of depression revealed that patients with major depressive disorder showed pronounced retardation but dysthymic patients did not show any retardation. Psychomotor retardation was more severe in patients with major depressive disorder with melancholic features. CONCLUSION: Psychomotor retardation can play an important role in the diagnosis and treatment of depressive disorders.

The abnormal development of drive and guidance mechanisms in the brain: the pathogenesis of schizophrenia.

BACKGROUND: It remains a mystery as to how genetic and environmental factors cause schizophrenia. OBJECTIVE: To develop a pathophysiological model of schizophrenia that has greater explanatory power than existing hypotheses of the disorder. METHOD: Published findings on schizophrenia are integrated with more recent data from human and animal studies of striatal and cerebellar functions. RESULTS: The analysis shows that during phylo- and ontogenesis two primarily motor-control mechanisms are applied at the intentional (limbic) level of functioning to organize emotional and cognitive behavior: one for initiating and dosing (drive) and the other for the representational guidance (guidance) of both movements and intentions. The intentional drive and guidance mechanisms are organized through a ventral, respectively, a dorsal cortical-subcortical circuitry. CONCLUSIONS: A deficient implementation of these mechanisms at the limbic domain manifests itself as schizophrenia, whereby the heterogeneity in symptomatology is explained by the extent of the remaining cerebral activity and by the degree of indirect activation of these systems. In general, activation manifests itself as positive symptomatology and the absence of such activation as negative symptomatology. The model provides a more comprehensive explanation for existing clinical and epidemiological data than do the current alternatives. It is compatible with the major prevailing views on the illness, such as the theories that regard this as a progressive neurodevelopmental, or a connectivity disorder, or one resulting from a deficient cerebral lateralization, or an interrupted cortico-thalamo-cerebello-cortical circuitry. The model fits with recent theories in evolutionary psychology and evolutionary psychiatry.