Background. The study examines the effect of an auditory discrimination task on regional brain perfusion in schizophrenic patients.

Methods. Twenty patients were examined with single photon emission tomography (SPET), both resting and performing an auditory two-tone ‘oddball’ discrimination task. Statistical parametric mapping (SPM'95) was used to identify local activation effects and correlations between event related potential measures and regional perfusion.

Results. Compared with rest, patients activated left superior temporal gyrus during the task, together with right caudate. There was a (negative) correlation between P300-amplitude and perfusion during the activation procedure in both caudate nuclei and in the left lingual gyrus. No correlations were observed with P300-latency. Compared with healthy volunteers examined in earlier studies, our patients showed no frontal activation. This might be due to slightly different task demands in this study, but more likely to activation-hypofrontality in schizophrenic patients compared with controls.

Conclusion. Auditory discrimination tasks can be used in schizophrenic patients to control their ‘mental set’ during brain perfusion studies with SPET. This approach can yield information about specific brain mechanisms associated with such tasks, and may make comparison with healthy volunteers easier.