Angus MacDonald | PubMed Health

PubMed2005

Prefrontal functioning during context processing in schizophrenia and major depression: an event-related fMRI study.

Patients with schizophrenia frequently demonstrate hypofrontality in tasks that require executive processing; however questions still remain as to whether prefrontal cortex dysfunctions are specific to schizophrenia, or a general feature of major psychopathology. Context processing is conceptualized as an executive function associated with attention and working memory processes. Impairment in the ability of patients with schizophrenia to represent and maintain context information has been previously reported in a number of studies. To examine the question of the specificity of a context processing deficit to schizophrenia, we used functional MRI and an expectancy AX continuous performance task designed to assess context processing in a group of healthy controls (n=9), depressed patient controls (n=10), and patients with schizophrenia (n=7). The behavioral performance was consistent with a context processing deficit in patients with schizophrenia, but not those with depression. The imaging data replicate previous results in showing abnormal activity in the right middle frontal gyrus (BA9) in schizophrenia patients related to context processing.

Adult↗

PubMed2005

Lateral and medial hypofrontality in first-episode schizophrenia: functional activity in a medication-naive state and effects of short-term atypical antipsychotic treatment.

OBJECTIVE: The dorsolateral prefrontal cortex and the anterior cingulate cortex are critical components of the brain circuitry underlying executive control. The objective of this study was to investigate control-related dorsolateral prefrontal cortex functioning and conflict-related anterior cingulate cortex functioning in a group of never medicated first-episode schizophrenia patients to determine whether both regions show dysfunction at illness onset. A second objective was to assess short-term effects of atypical antipsychotic medication on dorsolateral prefrontal cortex and anterior cingulate cortex functioning. METHOD: First-episode schizophrenia patients (N=23) and healthy comparison subjects (N=24) underwent event-related fMRI and performed a cognitive task designed to functionally dissociate the two regions. Four weeks after initiation of pharmacotherapy for patients, a subset of 11 patients and 16 comparison subjects underwent a repeat assessment. RESULTS: At baseline, patients exhibited hypoactivation in the dorsolateral prefrontal cortex and anterior cingulate cortex. After 4 weeks of antipsychotic treatment, the patients demonstrated improved functioning in the anterior cingulate cortex but not in the dorsolateral prefrontal cortex. CONCLUSIONS: These findings confirm the presence of dorsolateral prefrontal cortex dysfunction early in the course of schizophrenia and suggest that anterior cingulate cortex functioning may be altered at illness onset as well. Results also suggest that anterior cingulate cortex functioning may be especially sensitive to remedial antipsychotic treatment effects. These findings are consistent with an emerging literature documenting short-term benefits of atypical antipsychotic medication for the neural circuitry underlying cognitive deficits in schizophrenia.

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