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Auteur : Landgraf Steffen
Cognitive Markers in Psychosis: Reference Frames in Spatial Cognition and Visual Scanning-Strategies as Stage Markers in Schizophrenia
Université Paris VI, Pierre et Marie Curie, 2010 (24/08/2010), thèse n° 1234

Formation doctorale :
3c Cerveau Cognition Comportement

Résumé :

Scientifically examining complex psychiatric disorders, such as schizophrenia, allows 1) establishing effective intervention and early detection measures, 2) identifying etiological underpinnings, and 3) making inferences on the understanding of human brain functions. Cognitive disturbances have long been considered core deficits of schizophrenia but only recently major advances have been reached in that domain. The present work presents a literature review based model that provides evidence that cognitive deficits in schizophrenia are mediated by impairments of the visual system. Twenty-four stabilized schizophrenia outpatients and 25 matched healthy individuals were tested in three visuo-spatial tasks: Pattern Recognition, Analogical Reasoning, and Spatial Referencing. During the former two tasks, eye movement recordings identified strategies. Further, task difficulty was varied while stimulus surface characteristics were held constant. In the latter task, peri- and extrapersonal space referencing and switching was tested behaviorally. In the Pattern Recognition and Analogical Reasoning tasks, patients showed behavioral deficits that paralleled information acquisition aberrations. They had longer reaction time in the easiest condition (identity) and higher error rate in the more difficult conditions (vertical, horizontal, diagonal) compared to controls. Patients did not adapt their fixation duration to task demands, resulting in higher fixation duration in the identity condition (Pattern Recognition only) and lower fixation duration in the diagonal condition. In the Analogical Reasoning task, patients deployed a more efficient information acquisition strategy (‘constructive matching’) less often than healthy controls in all except the most difficult (diagonal) condition. In the Spatial Referencing Task, patients showed intact reaction time and reaction time improvement during egocentric referencing. They were slower and improved less than controls during allocentric referencing. Patients’ switching between egocentric and far-allocentric (landmark-centered) referencing was impaired. These results indicate that visuo-spatial deficits are mediated by information acquisition strategies in schizophrenia. Patients do not adapt fixation duration to task demands and use inefficient strategies more often than healthy controls. In fact, patients employ a ‘one-fits-all-task-demands’ strategy, which becomes maladaptive when task demands become too high or too low. Further, the results suggest that patients’ egocentric referencing is generally unimpaired. However, allocentric referencing and switching between egocentric and landmark-centered perspectives are impaired. This suggests that disturbances in non-egocentric referencing and transferring efficiently between referential systems might be the source of altered personal and social world comprehension in schizophrenia. Overall, these results provide evidence that cognitive deficits are mediated by impairments of the visual system. This has important treatment and research implications. Specifically, patients’ performance might be improved by training them in flexible, adaptive strategy deployment. Efficient self and social world comprehension might rely on proper allocentric referencing. The proposed model harmonically integrates findings from a plethora of literature on visuo-spatial cognitive deficits and helps to unravel the mysteries of one of the most devastating disorders of our time.

Mots clés
spatial referencing - Schizophrenia - Information acquisition strategies - cognitive dysfunctions - switch cost - neurocognition - Eye movement recordings - behavioral -


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Landgraf S, Amado I, Purkhart R, Ries J, Olie JP, van der Meer E
Visuo-spatial cognition in schizophrenia: Confirmation of a preference for local information processing.
Schizophr Res, 2010; (PMID 21186098).

Landgraf S, Krebs MO, Olie JP, Committeri G, van der Meer E, Berthoz A, Amado I
Real world referencing and schizophrenia: are we experiencing the same reality?.
Neuropsychologia, 2010; 48: 2922-30 (PMID 20540956).

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