Which is the neuropsychological meaning of perseveration in paranoid schizophrenic patients in the Wisconsin Card Sorting Test?

Various investigations indicate that perseveration is a common neuropsychol ogical sign of schizophrenia, resulting from the lack of cognitive flexibil ity, secondary to the dysfunction of the frontal lobe. However, from a semi ological point of view, per severation may have different neuropsychologica l meanings. In most of the results obtained by means of the application of the Wisconsin Card Sorting Test (WCST) this sign has been interpreted as a direct consequence of the incapability of patients for making a fast compar ative change between the different concepts and for adopting different pers pectives about a concept without analyzing other possible causes of failure in the fulfillment of this task. The purpose of this work was that of anal yzing in detail the different dimensions of the WCST for evaluating, in a s emiologic way, the nature of the perseverative answers. This instrument was the applied to a group of 30 paranoid schizophrenic patients, compared to 30 healthy subjects, paired by age, sex and academic education. The group was compared by means of simple ANOVA in the three WCST dimension s, and two matrixes of partial correlations, controlled by the number of as seys used for analyzing the relation between these variables; the correlati on coefficients obtained for each group were compared by means of Fisher's Z contrasts. Finally, the answering trains (positive and negative) were ana lyzed by means of Grant's G(2) test for tridimensional contingence tables. Results suggest that schizophrenic patients have important deficiencies for confronting this paradigm, and actually commit a significantly higher numb er of perseverative answers. However, perseveration in these patients, more than reflecting their lack of cognitive flexibility, seem to relate to def fects in the abstraction and comprehension of the problem.