In the wake of limited knowledge on clustering and switching during semantic fluency (SF) in patients with first-episode psychosis (PwFEP), the present study aimed (1) to investigate clustering and switching on SF in PwFEP using more precise statistical procedures and (2) to investigate the possibility of disproportionate clustering patterns across different SF tasks in PwFEP and healthy subjects (HS), as this has been indicated by the current literature on patients with schizophrenia. We recruited 22 PwFEP and 22 HS matched in age, sex distribution, and handedness. All patients were medicated and had a mean illness duration of 1 month (median: 0). Five categories were administered for SF: animals, trees, vegetables, fruits, and musical instruments (60 seconds each). PwFEP produced significantly fewer correct words in the aggregate score, as well as across all categories. The switching rate was significantly higher in PwFEP, but no post hoc comparisons were significant. PwFEP also produced significantly smaller clusters, yet the post hoc comparisons for the tree and fruit task were not significant. A higher switching rate and smaller clusters indicate less efficient functional connectivity within subcategories of the given categories, but not necessarily between the subcategories. Although both less likely to produce a cluster once a switch has been uttered and less likely to produce clusters larger than two words compared to HS, the latter deficit was more pronounced. Possibly, PwFEP might have greater difficulty in processing more concrete compared to more abstract concepts. Finally, our results also indicate that there are category-specific effects on the clustering deficit in PwFEP, possibly demonstrating that PwFEP might show normal performance on executively more demanding SF subtasks. We discuss the results in the context of the hypothesis of semantic hyperactivation in schizophrenia.
Computational linguistic analysis applied to a semantic fluency task to measure derailment and tangentiality in schizophrenia
