Auditory Event‐Related Potentials (P300) and Regional Cerebral Blood Flow in Elderly Depressed Patients

Abstract

Background:In order to evaluate the degree of impairment of cerebral function and the organic factors involved in elderly depressed patients, auditory event‐related potentials (ERP; P300) and N‐isopropyl‐p [123I] iodoamphetamine (123I‐IMP) single photon emission computed tomography (SPECT) were examined. Methods:Three groups of patients, the depression (D) group, consisting of 23 cases where the magnetic resonance imaging (MRI) showed no abnormalities, the depression with silent cerebral infarction (D/SCI) group, consisting of 28 cases with silent cerebral infarction, and the post‐stroke depression (D/PS) group, consisting of 19 cases at over six months after onset of cerebral infarction where no abnormalities in intellectual function were seen, but neurological symptoms such as hemiplegia were present, and 27 healthy individuals were investigated. All of the patients fulfilled the ICD‐10 diagnostic criteria for depressive episode, and disease onset occurred when the patients were over 55 years. The ERP (P300) was recorded using a tone discrimination task. Regional cerebral blood flow (rCBF) was measured by 123I‐IMP SPECT, and the relative rCBF of each region of interest was evaluated by comparison with the mean cerebellar rCBF. In addition, the mean cerebral blood flow (MCBF) in the cerebral cortex was assessed. Results:The D group included many cases in which the P300 peak latency was relatively short and the MCBF was stable, relative to the other two groups. In the D/PS group, there were many cases where the P300 peak latency was prolonged and the MCBF was reduced. In the D/SCI group, many differences in the results from both indicators existed among individual cases, and no fixed trend was identified. Conclusion: From the perspective of determining therapeutic tactics for elderly depressed patients and forecasting prognosis, it is important to review in detail, on an individual basis, components such as higher brain functions including cognitive functions, cerebral circulatory dynamics, and psychological/environmental factors. We believe that it is useful to evaluate a combination of factors when making such a review, including diagnostic imaging such as MRI, ERP (P300), and rCBF.