AUDITORY ATTENTIONAL DEFICITS IN PATIENTS WITH SCHIZOPHRENIA - A POSITRON EMISSION TOMOGRAPHY STUDY

Background: Patients with schizophrenia have frequently been found to perform poorly on tasks requiring selective attention, defined as the ability to focus attention on relevant information while simultaneousl y ignoring irrelevant stimuli. This study explores the brain mechanism s mediating attentional processing in patients with schizophrenia by m easuring their regional cerebral blood flow (rCBF) with positron emiss ion tomography using [O-15] water as they performed tasks that differe d systematically in attentional demand. Methods: Ten schizophrenic pat ients (either neuroleptic-naive or withdrawn from medication) (patient group) and 10 normal volunteers (control group) performed auditory ta rget detection tasks. Different types of auditory stimuli (environment al sounds, meaningless speech sounds, and words) were presented either binaurally (ie, same sounds in both ears) or dichotically (simultaneo us and different sounds in the 2 ears). In dichotic conditions, subjec ts were instructed to focus on either their left or right ear. Results : Initial subtraction-based image analyses sought significant rCBF cha nges anywhere in the brain. Patients consistently had less significant activation than controls in right superotemporal gyrus (STG). Follow- up analyses used regions of interest traced on individual magnetic res onance images to precisely measure rCBF in STG. Unlike controls, patie nts had higher rCBF in the left STG during all activation conditions. Conclusions: The abnormal task-related rCBF asymmetry in STG of schizo phrenic patients may indicate an isolated temporal lobe deficit, but i t may also indicate abnormality in the thalamocortical circuitry media ting selective attention and/or in the brain systems that integrate au ditory processing in the 2 hemispheres.