PubMed · 9884870
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L S Rasmussen. 1998. Defining postoperative cognitive dysfunction.. https://doi.org/10.1097/00003643-199811000-00026
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Behavioral deficits suffered by patients with schizophrenia in a wide array of cognitive domains can be conceptualized as failures of cognitive control, due to an impaired ability to internally represent, maintain, and update context information. A theory is described that postulates a single neurobiological mechanism for these disturbances, involving dysfunctional interactions between the dopamine neurotransmitter system and the prefrontal cortex. Specifically, it is hypothesized that in schizophrenia, there is increased noise in the activity of the dopamine system, leading to abnormal "gating" of information into prefrontal cortex. The theory is implemented as an explicit connectionist computational model that incorporates the roles of both dopamine and prefrontal cortex in cognitive control. A simulation is presented of behavioral performance in a version of the Continuous Performance Test specifically adapted to measure critical aspects of cognitive control function. Schizophrenia patients exhibit clear behavioral deficits on this task that reflect impairments in both the maintenance and updating of context information. The simulation results suggest that the model can successfully account for these impairments in terms of abnormal dopamine activity. This theory provides a potential point of contact between research on the neurobiological and psychological aspects of schizophrenia, by illustrating how a particular physiological disturbance might lead to precise and quantifiable consequences for behavior.
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A PRACTICAL TOOL: Screening for cognitive deficiency has been considerably improved by the use of a standardized tool, the Mini-Mental State Examination (MMSE). The MMSE only takes a few minutes and furnishes quantitative data for comparison between patients and to follow the evolution of a given patient. AN IMPORTANT ROLE: The MMSE is particularly useful for screening for dementia and states of mental confusion. It should be used systematically for elderly subjects, not only in the neurology setting, but also in geriatrics, psychiatrics and internal medicine. INTERPRETATION: The global score gives an assessment of the subject's performance level, taking into account for age, affective status and cultural situation. The MMSE cannot alone provide the diagnosis of dementia which requires a complete neurological examination. THE CONSENSUAL FRENCH VERSION: Diverse French versions have been developed with considerable differences in scoring schemes. For this reason, the Working Group on Cognitive Evaluations (GREC) has established a consensual version of the MMSE in French.