The left medial temporal region and schizophrenia. A PET study.

Regional cerebral blood flow (rCBF) was measured in 30 schizophrenic patients with severe, persistent and stable symptoms using positron emission tomography (PET). Directed and non-directed correlational analysis of the relationship between psychopathology and rCBF was used to identify brain structures implicated in three behavioural subsyndromes of schizophrenia. Psychopathology and neurophysiology (rCBF) exhibited high correlations in the left medial temporal region, mesencephalic, thalamic and left striatal structures. The highest correlation was in the left parahippocampal region. A canonical analysis of the same data highlighted the left parahippocampal region and left striatum (globus pallidus) as sites which linked the behavioural subsyndromes in terms of shared rCBF correlates. Increasing severity of psychopathology was associated with increased rCBF in these regions. Disinhibition of left medial temporal lobe activity mediated by fronto-limbic connections is a possible explanation for these findings; however, the prefrontal component appears to be critically dependent on the behavioural subsyndrome.