Arguments against the cognitive dysmetria hypothesis of schizophrenia

Modeling psychological function in patients with schizophrenia with the PANSS: an international multi-center study

BACKGROUND

The aim of the current study was to explore the changing interrelationships among clinical variables through the stages of schizophrenia in order to assemble a comprehensive and meaningful disease model.

METHODS

Twenty-nine centers from 25 countries participated and included 2358 patients aged 37.21 ± 11.87 years with schizophrenia. Multiple linear regression analysis and visual inspection of plots were performed.

RESULTS

The results suggest that with progression stages, there are changing correlations among Positive and Negative Syndrome Scale factors at each stage and each factor correlates with all the others in that particular stage, in which this factor is dominant. This internal structure further supports the validity of an already proposed four stages model, with positive symptoms dominating the first stage, excitement/hostility the second, depression the third, and neurocognitive decline the last stage.

CONCLUSIONS

The current study investigated the mental organization and functioning in patients with schizophrenia in relation to different stages of illness progression. It revealed two distinct "cores" of schizophrenia, the "Positive" and the "Negative," while neurocognitive decline escalates during the later stages. Future research should focus on the therapeutic implications of such a model. Stopping the progress of the illness could demand to stop the succession of stages. This could be achieved not only by both halting the triggering effect of positive and negative symptoms, but also by stopping the sensitization effect on the neural pathways responsible for the development of hostility, excitement, anxiety, and depression as well as the deleterious effect on neural networks responsible for neurocognition.

Cerebellum and cognition: viewed from philosophy of mind

Traditionally, it is believed, that the primary function of the cerebellum is to coordinate movement. During the past three decades, it has been controversially discussed, whether the cerebellum may also contribute to cognition and mental states like emotions. In this paper, no position relating to this controversy will be taken. Instead, the hypothesis of non-motor functions of the cerebellum will be viewed from the position of the philosophy of mind. The remarkably uniform microscopic structure and neuronal networks of the cerebellum have led to computer analogies by several authors. The main idea of functionalism, i.e., a theory within the philosophy of mind, is that the mental relates to the physical as computer software does to hardware. This raises the question, whether a cerebellar contribution to cognition and mental states would support functionalism in the philosophy of mind. No support of functionalism could be found in this study, investigating the classical philosophical arguments pro and con functionalism such as those of multiple realizability, the Chinese room and the explanatory gap, while taking the results of cerebellar research into account. On the other hand, philosophical reflection suggests a careful use of the phrases "cognitive dysmetria" (Andreasen et al. Proc Natl Acad Sci USA. 1996;93:9985-90) in the context of mental illness and of "dysmetria of thought" (Schmahmann Arch Neurol. 1991;48:1178-87). According to the argument of the explanatory gap there is at present little support for the assumption that the phenomenal experiencing of an altered emotion can be reduced to the dysmetria of movement.