• D Sander, O Koenig, N Georgieff, J-L Terra, and N Franck.
• Geneva Emotion Research Group, Section de Psychologie, Université de Genève, 40, boulevard du Pont d'Arve, CH-1205 Genève, Suisse.
• Encephale. 2005 Nov 1;31(6 Pt 1):672-82.

AbstractSchizophrenia is a disease that constitutes a particularly relevant way to investigate emotional processing. Indeed, major clinical signs of emotional disturbance (eg, anhedonia) suggest that some emotional mechanisms are defective in patients with schizophrenia. Evaluation can be considered as a fundamental component of the emotional system (28) and the first aim of the present study was to test the polarity hypothesis according to which different mechanisms are involved in the evaluation of positive vs negative emotional events. The second aim was to disentangle a -paradox emerging from the schizophrenia literature. On one hand, the tendency that schizophrenic patients have to under-evaluate the level of unpleasantness of negative stimuli suggests a deficit in the evaluation of negative events. For instance, it was proposed that patients with schizophrenia show a major deficit in the recognition of negative emotions, but a preserved recognition of positive emotions. On the other hand, the fact that anhedonia constitutes a critical cli-nical feature of schizophrenia suggests a deficit in the eva-luation of positive events. For instance, Crespo-Facorro et al. showed that patients with schizophrenia had a tendency to under-evaluate the level of pleasantness of positive stimuli but correctly evaluated the level of unpleasantness of negative stimuli. Given the importance of the social component in the analysis of deficits in patients with schizophrenia, we hypothesized that the variation of this component in stimuli used in the literature could explain the apparently inconsistent results described above. For example, the Bell et al. study used social stimuli whereas the Crespo-Facorro et al. study used non-social stimuli. Therefore, in our study, we have decided to manipulate the social component of stimuli. Another research issue of the present experiment was to study the explicit and/or implicit mode of processing of eva-luation in schizophrenic patients. In general, the experimental logic was to expect interaction effects between the factors polarity (negative vs positive) and participants (schizophrenic patients vs controls). Moreover, given the potential importance of the social component, a three-way interaction of the factors polarity, participants, and social component was expected. Finally, the experimental paradigm allowed us to search for dissociations in the context of both explicit and implicit evaluation. Stimuli used were negative and positive emotional pictures from the International Affective Picture System. Stimuli were chosen so that the mean valence -ratings of negative and positive pictures were at the same distance from neutrality. The factor arousal was controlled so that negative and positive pictures had equivalent mean arousal ratings. The social component factor was operatio-nalized by selecting pictures that either depicted or not a social scene. A fundamental criterion was that all social pictures were depicting at least one human being (eg, a wedding or a funeral), whereas non-social pictures never depicted any human being (eg, animals and landscapes). An upper and a lower border, that were either identical or different, were added to each picture. In a first experiment (the "implicit-task experiment"), patients with schizophrenia and matched controls were requested to decide whether the two borders surrounding the pictures were identical or different. Asking participants to process the borders was an experimental ruse to test if emotional processing takes place even when it is not task-relevant, and therefore if it is implicit. In a second experiment (the "explicit-task experiment"), the same participants were requested to evaluate whether the pictures were pleasant or unpleasant. Analyses of variance (ANOVA) were computed on response time and number of correct responses for both tasks. An important result was the observation of the expected three-way interaction effect of the factors polarity, participants, and social component on response time in the explicit task F(1, 19)=4.8, p<0.05. Critically, we observed that, for non-social stimuli, the interaction effect of the factors participants and polarity on response time was significant in the explicit task, F(1, 8)=4.9, p<0.05. These results are consistent with the polarity hypothesis and suggest a deficit in the processing of non-social positive stimuli in patients with schizophrenia. The expected three-way interaction effect was also observed on the number of correct responses in the explicit task F(1, 19)=5, p<0.04. For this task, we critically observed that, for social stimuli, the interaction effect of the factors participants and polarity on the number of correct responses was significant F(1, 19)=8.4, p<0.04. These results are also consistent with the polarity hypothesis and suggest a deficit in the processing of social negative stimuli in patients with schizophrenia. Moreover, let us notice that a comparison of the performances of the two groups revealed that patients made significantly more errors than controls for the evaluation of non-social positive stimuli, F(1, 19)=10,5, p<0.001, but not for the evaluation of non-social negative stimuli, F<1. In the implicit-task experiment, the analysis revealed that patients had a tendency to make more errors in the judgment of borders configuration for negative than for positive stimuli, whereas control participants showed the opposite tendency F(1, 19)=5.7, p<0.03, for the interaction of the factors polarity and participants. This result is consistent with the idea that distinct cognitive mechanisms are involved in the evaluation of positive vs negative emotional events even in the context of implicit processing. In conclusion, results obtained support the hypothesis according to which different cognitive mechanisms are involved in the evaluation of positive vs negative emotional events. Moreover, results suggest that patients with schizophrenia show a deficit in hedonic judgment of social negative and non-social positive stimuli. The later result indicates that the paradox described above becomes clearer whenever the social component of emotional stimuli happens to be taken into account. Results suggest that the polarity and the social component of events evaluated by patients with schizophrenia are critical parameters that should be considered in forthcoming studies that investigate affect disorders in schizophrenia.

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