Event-related fMRI study of prefrontal and anterior cingulate cortex during response competition in schizophrenia

Carter et a]. [Science 280 (1998) 747] demonstrated that anterior cingulate cortex (ACC) detects conditions in which errors are likely to occur. Kirino and Belger [E. Kirino, A. Belger, fMRI and ERP evidence of prefrontal cortex mediation of novelty bias and distractibility in schizophrenia, in: K. Hirata, Y. Koga, K. Nagata, K. Yamazaki (Eds.), Recent Advances in Human Brain Mapping, Elsevier, Amsterdam, 2002, pp. 691 -696.] further observed aberrant prefrontal cortex (PFC) activation during a visual oddball paradigm containing task-irrelevant distracters in schizophrenia. We hypothesized that schizophrenics show distorted PFC and ACC activation during response competition. We imaged patients and controls performing variants of Continuous Performance Test (CPT) that were designed to increase error rates and manipulate response competition. Subjects made a response whenever the probe was an X proceeded by a cue A, and to make a nontarget response to all other stimuli (AY, BX and BY). When targets (AX) occurred with 70% frequency, AY and BX were previously reported to elicit higher levels of response competition than BY (1998). Event-related design for the functional MRI (fMRI) experiment was employed with AX (p = 86%) as baseline response and AY, BX, and BY (p = 4.7% for each) as event stimuli. Echo Planner images were acquired on a 1.5-T MR system. Schizophrenics showed attenuated activation in PFC and ACC under condition that elicits response competition. These findings might indicate that they are less sensitive to override prepotent responses. Schizophrenics' deficits in working memory might be attributed to the deteriorated central executive system, which involved response competition, rather than slave systems in the working memory model of Baddeley [Science 255 (1992) 556]. (C) 2004 Elsevier B.V. All rights reserved.