Remitted schizophrenia-spectrum patients with spared working memory show information processing abnormalities.

Working memory and information processing abnormalities are often reported in schizophrenia. The aim of this study was to examine visual backward masking (BM) functions in remitted schizophrenia-spectrum patients with spared working memory functions. Seventy-two patients with DSM-IV schizophrenia-spectrum disorders were screened using the Wisconsin Card Sorting Test (WCST) and the digit span forward/backward tasks. Patients with spared WCST and digit span performances were selected and administered a spatial working memory test and two BM procedures (target identification and location). The schizophrenia-spectrum group with spared WCST and digit span performances included individuals with schizophreniform disorder (N=11), schizophrenia (N=2), and schizoaffective disorder (N=2). These patients were clinically remitted and demonstrated spared IQ, normal spatial working memory, and relatively high psychosocial functioning. However, there was a significant impairment in the BM procedure, most prominently in the target location task and at short interstimulus intervals. These results suggest that the BM dysfunction is a trait marker of schizophrenia-spectrum disorders and may be present in the absence of working memory abnormalities.

Category learning and perceptual categorization in schizophrenia.

The aim of this study was to evaluate category learning in schizophrenia on tests of perceptual abstraction. Participants learned to categorize simple geometrical shapes. The categories were either well-defined (discrete categories, or DCs) or ill-defined (graded categories, or GCs). In DCs, the cues defining category membership can be verbalized in an all-or-none fashion, while in GCs they cannot be defined unambiguously. Three types of learning were used successively: serial presentation of category-exemplars, verbal description, and feedback. After the serial presentation, schizophrenia patients showed a deficit for GCs (p<0.005) but not for DCs (p = 0.98). After the verbal definition of GCs, the difference between schizophrenia patients and controls diminished (p = 0.09). Finally, after the feedback learning of GCs, a significant difference was observed again (p<0.0001), suggesting that schizophrenia patients were impaired in this learning paradigm. The GC-learning impairment after the serial presentation displayed a relationship with the score of the cognitive component assessed with the Positive and Negative Syndrome Scale (r = -0.66). In conclusion, these results suggest that the perceptual stage of abstraction is impaired in schizophrenia. This impairment can be partially compensated by instructions via top-down verbal processes.

Abstraction is impaired at the perceptual level in schizophrenic patients.

This study investigates category learning in schizophrenia in order to evaluate abstraction abilities at the perceptual level. The participants learned about two categories of geometric shapes. The category exemplars were presented successively. In the case of schizophrenic patients, longer exposure time and more stimulus presentations were used to counterbalance attention impairments. In spite of this, the perceptual category learning was significantly impaired in the patient group. In contrast, when the training procedure involved verbal category definition and not perceptual learning, the performance of schizophrenics was similar to that of the healthy controls. These findings suggest that the perceptual learning of categories, but not free classification judgements are impaired in schizophrenia, and that this impairment is not due to pure attentional disturbances.

[Testing basic visual functions in the evaluation of extrapyramidal side effects of antipsychotic agents]. / Elemi vizuális funkciók vizsgálata az antipszichotikumok által elP6dézett extrapyramidalis mellékhatások követésében.

One of the cornerstones of antipsychotic therapy is the evaluation of the effective dose that cause minimal extrapyramidal side effects. It is known that the visual system (e. g. the retina) contains dopaminergic cells similarly to the striatum where dopaminergic blockade is crucial in the induction of extrapyramidal symptoms. This rises the possibility that striatal functions can be tested by the evaluation of certain visual functions. This study compared the visual contrast-sensitivity of 20 schizophrenic patients on antipsychotic medication (9 patients were on risperidone, 9 on haloperidol, and 1-1 on zuclopenthixol and fluanxol treatment) to that of normal control subjects, and found significant impairment in the former group. The contrast-sensitivity impairments correlated with the severity of extrapyramidal symptoms. These results suggest that contrast-sensitivity measurements can be useful in the evaluation of neuroleptic threshold in the clinical practice.