BACKGROUND: Cognitive impairments are often accompanied in patients with silent cerebral infarction (SCI) and depression, and there is still no reliable objective assessing method for the evaluation.OBJECTIVE: The purpose of this study was to probe into the value of auditory P300 in detecting the cognitive impairment in SCI patients with depression.DESIGN: A golden standard control study.SETTING: Department of Neurology, Xi 'an Central Hospital; Department of Neurology, the Second Hospital of Xi' an Jiao Tong University.PARTICIPANTS: Thirty-eight SCI patients were selected from the Outpatient Department of Neurology, the Second Hospital of Xi' an Jiao Tong University between January 2002 to May 2003, including 10 got dizziness,11 got poor concentration, 8 got headache, 5 got numbness of extremities and 4 got syncope. Among them, 26 were detected by CT and 12 by MRI.The patients'aged 45 to 63 years with mean age of (57.3±5.1) years, including 20 males and 18 females.METHODS: The existence of depressive symptoms was measured with the 17-item Hamilton depression scale (HAMD). In this scale, the total score ranged from 0 to 52, with higher score indicating more severe depressive symptoms, and the patient was considered as having depression if the HAMD score was ≥ 9. HAMD tests were administered by two psychiatrists,who were experienced in psychiatric disorders in stroke and other somatic diseases, and the two psychiatrists had a better coincidence (Kappa=0.86 -0.91). The auditory event related potential was detected with MYTO serial cerebra induced potential meter, while lying in a bed placed in a sound-attenuated room. Auditory stimuli were delivered binaurally through headphones. The subject was required to distinguish between the tones by noting the occurrence of the target and not to respond to the standard. All patients underwent a routine experimental test at first, and then a normal test was performed to obtain a better coincidence. Mini-mental state examination (MMSE) was conducted for the 38 patients by specialized training neurologist to assess the cognitive impairment, in which the total score ranged from 0 to 30, with lower score indicating greater impairment. The criteria of intellectual deterioration was defined on the basis of educational level:MMSE score of 17 for illiterate, 20 for primary school and 24 for middle school and above.MAIN OUTCOME MEASURES: The score of MMSE, latent period of P300 wave and amplitude of P300 wave were mainly observed.RESULTS: All the 38 cases were involved in the final statistical analyhave depressive symptoms (47%, depression group) and 20 had no depresindexes and score of MMSE between the SCI patients with and without depression: As compared with the SCI patients without depression, the P300 latent period was obviously prolonged, the P300 amplitude and MMSE score were markedly decreased in the SCI patients with depression [(383.3±31.1), (347.2±37.3) ms; (5.6±0.7), (9.9±1.6) μV; (15.2±1.1),and P300 indexes: In the SCI patients with depression, the P300 latent period had significant negative correlation with the MMSE score (r=-0.549, P ＜ 0.05), the P300 amplitude had significant positive correlation with the MMSE score (r =0.525, P ＜ 0.05). However, there was no correlation between the latent period and amplitude of P300 and the MMSE score in the SCI patients without depression (r=-0.349 to 0.065, P ＞ 0.05).CONCLUSION: Depression and cognitive impairments may have the same pathophysiological basis in SCI patients. P300 can be used as a referential and objective method to analyze the cognitive function in SCI patients with depression.