Olfactory identification and Stroop interference converge in schizophrenia

Abstract

Objective: To test the discriminant validity of a model predicting a dissociation between measures of right and left frontal lobe function in people with schizophrenia.

Participants: Twenty-one clinically stable outpatients with schizophrenia.

Interventions: Patients were administered the University of Pennsylvania Smell Identification Test (UPSIT), the Stroop Color-Word Test (Stroop), and the Positive and Negative Syndrome Scale (PANSS).

Outcome measures: Scores on these tests and relation among scores.

Results: There was a convergence of UPSII and Stroop interference scores consistent with a common cerebral basis for limitations in olfactory identification and inhibition of distraction. There was also a divergence of UPSIT and Stroop reading scores suggesting that the olfactory identification limitation is distinct from a general limitation of attention or a dysfunction of the left dorsolateral prefrontal cortex. Most notable was the 81% classification convergence between the UPSIT and Stroop incongruous colour naming scores compared with the near-random 57% classification convergence of the UPSIT and Stroop reading scores.

Conclusions: These data are consistent with a right orbitofrontal dysfunction in a subgroup of patients with schizophrenia, although the involvement of mesial temporal structures in both tasks must be ruled out with further study. A multifactorial model depicting contributions from diverse cerebral structures is required to describe the pathophysiology of schizophrenia. Valid behavioural methods for classifying suspected subgroups of patients with particular cerebral dysfunction would be of value in the construction of this model.