目的探讨改变P300 靶刺激概率对事件相关电位P300 潜伏期和波幅的影响。方法2014 年1~12 月就诊的记忆力减退患者35 例，分别进行靶刺激概率为0.10 和0.25 的事件相关电位P300 检查，分析P300 波的潜伏期、波幅及波幅下面积。结果两种靶刺激概率下，P300 潜伏期无显著性差异(t<0.256, P>0.800)，波幅和波幅下面积均有显著性差异(t>4.259, P<0.05)。结论低概率靶刺激可能由于提高了患者的注意力而使波幅增高。P300 潜伏期不易受患者注意力干扰，是判断认知功能最重要的指标。

Objective To observe the latency and amplitude characteristics of event-related potential P300 under different target stimulus. Methods During January to December, 2014, 35 patients with memory impairment received P300 test under the percentage of target stimuli of 0.10 and 0.25. The latency, amplitude and area under amplitude were compared. Results There was no significant difference in latency (t<0.256, P>0.800), but the amplitude and area under amplitude increased under 0.10 compared with those under 0.25 (t>4.259, P< 0.05). Conclusion Less target stimulation may improve the patients' attention and increase amplitude of P300, but no more interference in latency, suggesting latency of P300 is more stable for assessment of cognitive function.