Neural correlates of formal thought disorder in schizophrenia - Preliminary findings from a functional magnetic resonance imaging study

Background: Formal thought disorder (FTD) is a core symptom of schizophreni a, but its pathophysiology is little understood. We examined the neural cor relates of FTD using functional magnetic resonance imaging. Methods: Blood oxygenation level-dependent contrast was measured using func tional magnetic resonance imaging while 6 patients with schizophrenia and 6 control subjects spoke about 7 Rorschach inkblots for 3 minutes each. In p atients, varying degrees of thought-disordered speech were elicited during each "run." In a within-subject design, the severity of positive FTD was co rrelated with the level of blood oxygenation level-dependent contrast in th e 2 runs that showed the highest variance of FTD in each patient. Results: The severity of positive FTD in patients was negatively correlated (P < .001) with signal changes in the left superior and middle temporal gy ri. Positive correlations were evident in the cerebellar vermis, the right caudate body, and the precentral gyrus. Conclusions: The severity of positive FTD was inversely correlated with the level of activity in the Wernicke area, a region implicated in the product ion of coherent speech. Reduced activity in this area might contribute to t he articulation of incoherent speech. Because of the small sample size, the se findings should be considered preliminary.