[Neurocognitive subtypes of schizophrenia according to performance at verbal fluency tasks]

There is a general agreement that schizophrenia is an heterogeneous disorder and cognitive performances could be an interesting feature in order to allow a better description of specific subtypes. The aim of this study was: 1) to describe clinical and neuropsychological performances of 45 DSM IV schizophrenic patients divided in two groups according to their performances in verbal fluency task; 2) to compare each group with the performances of healthy subjects matched for sex, age and education.

The differentiation criteria was the total number of words generated during 3 formal and 3 semantic fluency tasks. Data were analysed using a disjoint clustering procedure with Euclidean distance. A two cluster solution was considered optimal. Cluster S1 includes 21 schizophrenic subjects defined as low performer (range: 40-83, mean 66.7). Cluster S2 includes 24 schizophrenic subjects (range: 87-158, mean 102.8). All schizophrenic patients were clinically evaluated with SANS, SAPS and a psychosocial aptitude rating scale (PARS). Patients and controls were assessed with the following battery: verbal fluency, Trail making test A & B, Stroop test, Brown Peterson paradigm for evaluation of working memory.

Patients with low verbal fluency had significantly higher scores at the SANS and PARS. Furthermore, the low performers (cluster S1) were differentiated from those with better performances (cluster S2) by significantly poorer results in all neuropsychological tests. Comparison with healthy subjects indicated that cluster S1 patients also had significantly poorer results in all neuropsychological tests. Relative to their 24 controls cluster S2 patients performances was lower in all measures excepted in one subscore of the Stroop test and in the number of cluster produced. This later result could indicate that some capacities for willed intention were preserved in this group and that the alteration in verbal fluency performances were better explained by impairment of the other cognitive processes.

These findings point out that: 1) use of performance in cognitive executive task such as verbal fluency is a possible criteria in order to separate different types of schizophrenic patients; 2) in the two groups of schizophrenic subjects, various processes defects underline cognitive performances indicating the presence of different neurobiological dysfunctioning.