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David Baxter

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Underlying pathology in people at risk for schizophrenia uncovered
By Liam Davenport
19 November 2007
BMC Psychiatry 2007; 7: 61

In people at high risk for schizophrenia, the lateral temporal cortex plays a role in hallucinations, while the medial temporal lobe is involved in positive psychotic symptoms, say UK researchers in findings that also suggest a potential role for the cerebellum in the formation of delusions.

Previous investigations have indicated that distinguishable pathological processes underlie the different types of psychopathology seen in schizophrenia. However, such studies have often been small and confounded by the effects of antipsychotic medication, explain Heather Whalley and colleagues from the University of Edinburgh.

The team therefore performed functional magnetic resonance imaging (fMRI) on 69 individuals aged 16-24 years at high risk for schizophrenia, all of whom were antipsychotic na?ve throughout the study, and 20 matched healthy controls with no family history of psychotic illness.

The participants were assessed using the Hayling sentence completion task and an encoding/retrieval task during fMRI, yielding a total of 89 scans on the first experiment and 86 scans on the second. Eighty three individuals had usable scans from both experiments. The severity of positive psychotic symptoms was measured using the positive and negative syndromes scale, with items for hallucinations, delusions, and suspiciousness/persecution examined, the team reports in the journal BMC Psychiatry.

The main areas of brain activation on the sentence completion task were the left precentral gyrus, the inferior frontal gyrus, the medial/superior frontal gyrus, middle/superior temporal gyrus, cerebellum, and occipital lobes bilaterally.

For the encoding/retrieval task, the bilateral inferior frontal gyrus, superior/medial frontal gyrus, insula, parietal lobe, cerebellum, basal ganglia, thalamus, and hippocampus were stimulated during word classification, with similar areas activated during correct recognition and correct rejection.

Correlating the findings with symptom severity, the team found that activation of the left anterior middle temporal gyrus positively correlated with hallucinations score during sentence completion, and there was significant negative correlation between activation of the left posterior lobe of the cerebellum and suspiciousness/persecution score. There was also a significant positive correlation between the anterior and right-side cerebellum and delusion score.

On the encoding/retrieval task, there was a significant negative correlation between the suspiciousness/persecution score and activation in the bilateral medial temporal lobe on word retrieval, as well as with the anterior and posterior lobes of the cerebellum. There was also significant positive correlation between lentiform nucleus activation and delusion score.

On word classification, there was significant positive correlation between delusion score and posterior cerebellar lobe activation and significant negative correlation between hallucinations score and angular gyrus activation.

The team writes: "That the current results are seen in un-medicated high-risk subjects indicates these associations are not specific to the established illness and are not related to medication effects and hence may have relevance for the understanding of the biological basis of the disorder."

Abstract
 

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