Functional brain activity has been only studied marginally in schizoaffective disorder (SAD), a disorder whose nosological status is controversial. The present study investigated the prefrontal cortex (PFC) activity of schizomanic patients during performance of a working memory task.

13 schizoaffective patients, with current schizomanic episode (Young> 18); and 26 sex- and age-matched healthy controls underwent functional magnetic resonance imaging (fMRI) while performing baseline, 1-back and 2-back versions of the n-back task. Linear models were used to obtain maps of activations and deactivations in the groups.

During performance of the n-back task, controls showed activation in a cluster of frontal areas and de-activation in the medial orbitofrontal and anterior cingulate cortex. The SAD patients showed significantly less activation in prefrontal areas than the controls. They also showed a marked failure to de-activate in medial frontal cortex. The SAD patients’ impaired task performance was associated with both reduced activation of the dorsolateral PFC and reduced de-activation of the medial frontal areas.

Schizomanic patients show failure of activation in a network of cortical regions, and also a failure to de-activate the ventromedial PFC and anterior cingulate cortex. This latter area corresponds to the one of the components of the 'default mode network´. This pattern of abnormality is similar to that found by our group to characterise schizophrenia (failure to activate and failure to de-activate), but different from that which characterises manic patients (failure to de-activate only).