Cerebral activity

Cerebral activity in schizophrenia has been extensively investigated using PET to measure regional cerebral blood flow and glucose utilization (see Chapter.2.3.6). Single-photon emission CT and functional magnetic resonance imaging ( MRI) have also been applied.

Hypofrontality—decreased activity in the frontal lobes—has been widely studied in schizophrenia since the first report in 1974. The current view is that, whilst hypofrontality does occur in unmedicated subjects,(8) it is not an invariable finding,(9) and its interpretation is still debated. (!„9 It is seen most clearly when subjects are performing tasks, such as the Wisconsin Card Sorting Test, which require activation of the frontal lobes.

The most comprehensive analysis correlating regional cerebral activity with the clinical features of schizophrenia is that by Liddle and colleagues, showing that the three subsyndromes of chronic schizophrenia identified by factor analysis have their own characteristic patterns of blood flow. (1!> For example, subjects with psychomotor poverty are hypofrontal whereas those with prominent positive symptoms have increased activity in the temporal lobe, especially in the hippocampus. Other studies show that the latter region does not activate normally during cognitive tasks.

One conclusion drawn from these studies is that there is no one site of dysfunction in schizophrenia. Rather, its pathophysiology reflects abnormalities in various distributed circuits integrating specific cortical areas and subcortical nuclei. (8!2) The model of schizophrenia as a disorder of disturbed neural connectivity is considered further below.

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