Déficits des fonctions exécutives dans la schizophrénie selon les dimensions positive, négative et de désorganisation

Abstract

The aim of this study was to examine whether executive deficits underlie positive, negative and disorganisation of schizophrenia. The sample comprised 34 patients (30 males, 4 females) diagnosed with DSM-IV criteria (mean age = 35 ± 9.5 years; mean duration of illness since first psychotic symptoms = 10.2 ± 7 years; mean years of education = 11.7 ± 2.6). Evaluation of patients was performed after achieved sufficient remission (clinically stable for 4 weeks at least, no depressive symptoms at moment of cognitive testing and no medication change during the three last weeks). Symptom dimensions were evaluated using items drawn from the Positive And Negative Symptoms Scale (PANSS). The Negative factor comprised N1 (blunted affect), N2 (emotional withdrawal), N3 (poor contact), N4 (passive, apathetic), N6 (lack of spontaneity), G7 (stereotyped thinking) and G16 (active social avoidance). The Positive factor comprised P1 (delusions), P3 (hallucinatory behaviour), P5 (grandiosity), P6 (suspiciousness) and G9 (unusual thought content). The Disorganisation factor comprised P2 (conceptual disorganisation), N5 (difficulty in abstract thinking), G10 (disorientation) and G11 (poor attention). The mean total PANSS score was 63.3 ± 16 (mean of positive score = 14.3 ± 4.7; mean of negative score = 18.1 ± 6.3; mean of general score = 30.9 ± 8.5). Executive functions were examined through the Wisconsin Card Sorting Test (WCST), the Hayling Test (Tunisian version) and two semantic verbal fluency tasks (simple with one category “animals” and alternating with two categories “fruits and clothes”). Partial correlations between syndrome scores and cognitive scores were examined while holding the effects of other symptoms, age and education level constant. Severity of disorganisation symptoms correlated with high number of perseverative errors ( r = 0.47, P < 0.05) and total errors in the WCST ( r = 0.37, P < 0.05) and with reduced score of alternating semantic verbal fluency ( r = –0.39, P < 0.05). Severity of both negative and positive dimensions uncorrelated with performance of any of the executive tasks. Also, scores of the Hayling Test (time part B minus time part A; errors part B) and semantic simple verbal fluency (total of correct words) were uncorrelated with symptoms. The present study provides evidence that disorganisation dimension of the PANSS correlates specifically with impaired cognitive flexibility as reflected by high number of perseveration in the WCST and reduced set-shifting in semantic alternating verbal fluency.