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, 3 (1), 87-101

Patterns of Anterior Cingulate Activation in Schizophrenia: A Selective Review

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Patterns of Anterior Cingulate Activation in Schizophrenia: A Selective Review

Rick Adams et al. Neuropsychiatr Dis Treat.

Abstract

Background: Anterior cingulate cortex (ACC) dysfunction is implicated in schizophrenia by numerous strands of scientific investigation. Functional neuroimaging studies of the ACC in schizophrenia have shown task-related hypo-activation, hyper-activation, and normal activation relative to comparison subjects. Interpreting these results and explaining their inconsistencies has been hindered by our ignorance of the healthy ACC's function. This review aims to clarify the site and magnitude of ACC activations in schizophrenia, and sources of their variation.

Method: 48 studies of mnemonic and executive task-related activations in schizophrenia using both positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) were analyzed.

Results: Abnormal activations in schizophrenia were not restricted to the "cognitive" part of the ACC. Hypoactivations were most common, and were found in all types of tasks. Hyperac-tivations when found, were largely in n-back tasks.

Conclusions: Hypoactivations cannot be explained by poor performance, more demanding control conditions or chronicity of illness alone. Patients on anti-psychotic medication tended to show both greater ACC activation and better performance, although whether this is directly due to their medication or the resultant reduction in symptoms is unclear. The relationship between ACC rCBF and task performance is not straightforward. Future research should better control confounding factors and incorporate different levels of difficulty.

Keywords: anterior cingulate cortex; functional magnetic resonance imaging; positron emission tomography; schizophrenia.

Figures

Figure 1
Figure 1
This graph illustrates how schizophrenic subjects might show a relative task-related hypoactivation, while being hyperactive in absolute terms.
Figure 2
Figure 2
Sites of hyperactivation and hypoactivation in schizophrenia and mean activation in controls during mnemonic tasks (n-back and encoding, recognition and retrieval tasks). Most experiments gave just one point of maximal activation in the ACC but a few gave more. All are listed in Tables 1–3. The points anterior to the dashed grey line lie in rCZa, those posterior to the line lie in rCZp.
Figure 3
Figure 3
Sites of hyperactivation and hypoactivation in schizophrenia and mean activation in controls during executive tasks (the Stroop, Verbal Fluency, Go-NoGo and Continuous Performance tasks). Most experiments gave just one point of maximal activation in the ACC but a few gave more. All are listed in Tables 1–3. The points anterior to the dashed grey line lie in rCZa, those posterior to the line lie in rCZp.
Figure 4
Figure 4
A graph illustrating one possible relationship between ACC activity, task difficulty and schizophrenia. Adapted from Manoach’s (2003) theory of DLPFC activation in schizophrenia.

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