PubMed · 15773063
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F Oyebode. 2005. Cognitive processing in schizophrenia.. https://doi.org/10.1192/bjp.186.3.262
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Many patients with schizophrenia have pronounced deficits in the use of negative feedback to guide problem solving and learning, as seen on tasks like the Wisconsin Card Sorting Test. There is now a compelling body of evidence from nonhuman primates that suggests transient decreases in dopamine cell activity may reflect the occurrence of unexpected negative outcomes, such as the absence of an expected reward, and, generalizing to the human, the occurrence of negative feedback or the absence of expected reward. We present preliminary evidence that habenula projections to the midbrain are capable of producing a transient, but nearly complete, inhibition of dopamine neurons at a population level similar to that observed in behaving primates following an unexpected negative outcome. Human functional imaging studies offer further evidence that the habenula is activated following receipt of unexpected negative feedback or the absence of expected positive feedback. We present initial evidence that patients with schizophrenia lack appropriate modulation of habenula activity in response to feedback. Collectively, these data suggest that the habenula may play a critical role in mediating the feedback-processing deficits of schizophrenia.
Cognitive impairment in multiple sclerosis (MS) has received considerable interest over the last decades. Heterogeneous patterns of cognitive dysfunction have been reported in literature in relation to the subtype of the disease and the severity of specific cognitive domains affected. Event related potentials (ERPs), especially P300, have been employed to evaluate the cognitive decline in MS and neurophysiological findings agree with data obtained by neuropsychological testing. The objectivity, the reliability and the easy administration are the main features of ERP technique but more specific attention and memory tasks are needed to enhance the clinical value of the methodology. Moreover, ERP recording has the advantage of being feasible even in severe disabled patients. Finally, longitudinal ERP studies are required to investigate the natural course of cognitive dysfunction in MS, to estimate the prognostic value of subclinical defects in different clinical form of the disease and to evaluate clinical benefits of therapeutic and rehabilitative interventions.
Cognitive deficit can be an early feature in the course of multiple sclerosis, may occur clinically isolated, impacts on social activities and could reflect disease progression that is independent of physical disability with potential therapeutical consequences. Neuropsychological tests should be independent of motor coordination or visuo-spatial ability, but sensitive to subtle cognitive changes, exploring attention speed and working memory They could be included in brief batteries with good normative data and alternative forms for future therapeutic trials. We recommend for a brief battery of neuropsychological tests the inclusion of PASAT and two memory tests: the learning stage of CVLT and backward Digit Span with a total time duration of 30 min. A complementary tool could be a cognitive questionnaire for informant. After a relapse, cognitive assessment should be performed at least 8 weeks afterwards. If the patient presents with psychiatric symptoms, a specific assessment should be proposed before starting a complete cognitive assessment. Finally, we propose some red flags warranting neuropsychological screening: patients with a mild physical disability, but unable to maintain their professional activities, pathological laughing-crying, increased age and low educational level.