SIMULTANEOUS OBSERVATION OF REGIONAL CEREBRAL BLOOD-FLOW AND EVENT-RELATED POTENTIAL DURING PERFORMANCE OF AN AUDITORY TASK

Reduced amplitude of the P300 component has been reported consistently in patients with neurological and psychiatric disorders. It is unclea r, however, how such patients' cognitive dysfunction is related to the ir P300 abnormality. Further basic knowledge regarding neural substrat es for P300 generation is required for gaining an understanding of the pathological significance of the P300 amplitude reduction. To determi ne the brain structures involved in P300 generation, we observed the e vent-related potential and the regional cerebral blood now (rCBF) in 1 0 normal subjects performing an oddball discrimination of pure tones. The rCBF value was assessed quantitatively with the aid of single phot on emission computed tomography using technetium-99m hexamethylpropyle ne amine oxime. During the task performance, significant activation wa s observed in the posterior superior temporal and inferior parietal re gions of the right hemisphere. In addition, positive correlation of th e task-related increase in rCBF with the simultaneously recorded P300 amplitude was observed in the right but not the left posterior superio r temporal region. These findings indicate that activation of the righ t non-verbal auditory area might modulate P300 generation during pure- tone discrimination.