Objective: The anterior cingulate gyrus is a pivotal component of brain networks directing affective and cognitive functions, and abnormalities of the anterior cingulate gyrus may be involved in the pathophysiology of schizophrenia. However, magnetic resonance imaging studies of the morphology of this region have been few and the results inconsistent. Many of the studies have not accounted for confounding factors such as gender, handedness, or clinical variables such as neuroleptic exposure.

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... hod: The morphology and clinical correlates of the anterior cingulate gyrus were evaluated in a group of 30 righthanded male subjects with schizophrenia and a comparison group matched for age, sex, and handedness. The patient group was specifically designed to provide measures of multiple phenomenological differences such as severity of illness, duration of illness, and exposure to typical neuroleptics. Results: The patient group had a significantly larger left anterior cingulate gyrus volume relative to comparison subjects, whereas right anterior cingulate gyrus volume did not differ between groups. Depth of the left anterior cingulate gyrus was significantly correlated with neuroleptic exposure, indicating that greater exposure to neuroleptics was associated with greater cortical depth of this region. There was no significant relationship between anterior cingulate gyrus morphology and duration of illness or severity of symptoms. Conclusions: Anterior cingulate gyrus depth in subjects with schizophrenia is directly related to typical medication exposure (the greater the exposure, the thicker the anterior cingulate gyrus) but not to other clinical variables such as length of illness or symptom severity. Future research is needed to determine the functional consequences of these changes and relationship to atypical neuroleptic use. (Am J Psychiatry 2005; 162:1872-1878) The anterior cingulate gyrus is a pivotal component of brain networks directing affective and cognitive functions (1, 2). As part of the rostral limbic system, the anterior cingulate gyrus modulates internal emotional responses (2, 3). Cognitively, the anterior cingulate gyrus is considered to be an integral component of a variety of executive functions such as motivation, attention, working memory, learning (especially in novel situations and when overcoming habitual responses), decision making, and awareness and insight (1, 2, 4) . Structurally, the anterior cingulate gyrus is located bilaterally in the medial wall of the frontal lobes, following the curvature of the genu of the corpus callosum. The anterior cingulate gyrus is contiguous with the posterior cingulate; the two together form the cingulate gyrus. While the cingulate gyrus has the appearance of a single structural unit, functionally the anterior cingulate gyrus is quite different from the posterior cingulate gyrus, which is involved in visuospatial and memory function (2). Within schizophrenia research, several lines of evidence suggest that structural and functional abnormalities of the anterior cingulate gyrus are involved in the pathophysiol-ogy of the illness. In functional neuroimaging research, positron emission tomography (PET) studies have shown differences in error monitoring (5), working memory control (6, 7), and selective attention (8, 9) and decreases in dopamine activation (10), glucose metabolism (11), regional cerebral metabolism (12), and regional cerebral blood flow (13). Electrophysiological studies have shown decreased anterior cingulate gyrus activation and slowed reaction times during information processing in subjects with schizophrenia (14, 15). Postmortem studies have shown key cytoarchitectural changes in layer II of the anterior cingulate gyrus and a decreased density of nonpyramidal neurons (16, 17) upon microscopic exam of people with schizophrenia versus normal subjects. However, gross examinations of postmortem brains have not shown observable changes (18, 19) . The literature on the structure of the anterior cingulate gyrus in schizophrenia as determined with magnetic resonance imaging (MRI) is small and highly inconsistent. Of the studies focusing on the overall anterior cingulate gyrus, findings have shown both a lack of significant differences in anterior cingulate gyrus volume in patients rela-