Attenuated frontal activation in schizophrenia may be task dependent

Functional magnetic resonance imaging was used to examine the neural correl ates of two linguistic tasks in schizophrenia. Method: Five dextral male sc hizophrenic patients and five volunteers matched for demographic variables and task performance participated. Echoplanar images were acquired over 5 m in at 1.5 T while subjects performed two paced, covert tasks; (1) verbal fl uency: silent generation of words beginning with an aurally presented cue l etter, contrasted with silent repetition of the aurally presented word 'res t'; (2) semantic decision: deciding whether a visually presented cue word w as 'living or non-living' and silently articulating the response, contraste d with rest. Both tasks entailed language processing; only verbal fluency r equires the intrinsic generation of verbal material. Between-group differen ces in the mean power of experimental response to the semantic decision tas k were identified by a one-way analysis of covariance (ANCOVA), with a meas ure of stimulus-correlated motion as a covariate. Voxels demonstrating a si gnificant interaction between task and group were identified using a two-wa y ANCOVA. Results: In controls, both tasks were associated with activation of prefrontal cortex. In patients with schizophrenia there was a significan tly reduced newer of response in several prefrontal regions during verbal f luency relative to controls, a difference that was not evident for the sema ntic decision task. There was a significant group x task interaction in the left inferior frontal gyrus, left dorsolateral prefrontal cortex and the s upplementary motor area at voxel and regional levels of analysis. conclusio ns: Attenuation of frontal activation during cognitive task performance in schizophrenia does not represent a fixed deficit in frontal function, but m ay depend on the specific cognitive demands of the experimental task employ ed. (C) 1999 Elsevier Science B.V. All rights reserved.