performance of a verbal fluency task Regional brain activity in chronic schizophrenic patients during the

British Journal of Psychiatry (1995), 167, 343-349Since the classic study of Ingvar & Franzen (1974),there have been many investigations of schizophreniaby functional brain imaging (Andreasen eta!, 1992).Most (—‘6001o)have observed a relative reduction infrontal metabolism in patients scanned at rest(hypofrontality). However, many studies (—400lo)found no evidence of hypofrontality and a fewobserved hyperfrontality. There are good reasons whyresting scans of schizophrenic patients should lead tocontradictory results. Mental activity is associatedwith detectable brain activity even when no overtbehaviour occurs (e.g. Stephan et al, 1995).Schizophrenic patients vary widely in their currentmental state, and thus varying patterns of cerebralblood flow are to be expected in unselected groups.Liddle eta! (1992) confirmed that current symptomsare related to regional cerebral blood flow (rCBF).Hypofrontality (particularly in the left dorsolateralprefrontal cortex (DLPFC)) wasfound to be associatedwith psychomotor poverty (poverty of speech,flattening of affect, and motor retardation).However, even though schizophrenic symptomssegregate into clusters, and different patterns ofresting cerebral blood flow can be associated withthese syndromes, it remains likely that a coreabnormality is present in all schizophrenic patients.An important approach to the problem of thevariability in mental states during brain imaging isto control mental state, at the time of scanning, byapplying a psychological challenge. This involvespresenting a task during the scan which elicitsspecificmental processes. This method can not only reducevariability between subjects, but also highlight brainareas of interest. For this purpose, various studieshave used psychological tasks sensitiveto frontal lobedamage. When normal volunteers perform suchtasks, there is an associated increase in frontal bloodflow. However, in schizophrenic patients, whoperform such tasks poorly, this increase is oftenreduced or absent (Weinberger, 1986). Thisobservation is particularly marked in patients withnegative features (Andreasen et a!, 1992). At the