年老化视觉空间注意等级效应脑机制的研究

目的：应用“提示-目标”的视觉实验范式，以汉字提示不同等级的搜索范围并设置干扰，通过事件相关电位技术研究视觉注意年老化脑机制。方法：用青年和老年人各16名为受试对象，背景由三个同心圆组成，提示为汉字“大”、“中”、“小”，刺激材料是随机选取的大写英文字母，组成3个同心圆圈。“T”为靶刺激，“T”不是唯一的，受试对象按照提示搜索提示范围上的靶刺激，忽略其它范围里的“T”。结果：随着提示等级的减小，两组反应时均加快，而早期ERP成分P1与N1波幅均增大，与青年组相比，老年组反应时更长，且后部P1显著增强和N1明显抑制，老年组前部P2成分亦受到显著抑制，这种抑制不仅表现在波幅上，还表现在波形的不规则和不稳定。结论：老年受试对象随任务的复杂度增加需要消耗更多的资源，与年老化的“复杂度效应”一致。老年组P2成分的显著抑制为首次发现，表明老年组受试对象对靶刺激的评估识别能力降低，提示年老化可能导致视觉空问注意的前脑区功能缺陷。

The scale effect of brain mechanism of aging on visual spatial attention

Objective: Using the visual experimental search model paradigm "precue-target",and that the research attentive range could be affected by different scale interference, the aging brain dynamic mechanisms on the visual attention were investigated through ERP technique.Method: 16 young and 16 old subjects participated the eleetrophysiological experiment. The background was comprised of three homocentrie black circles and eight English capital letters filled in each circle.The letter "T" was designed as the target stimulus. However, Two or more T letters were presented simultaneously.T was the only target when it located in the circle clued to the same size of the precue.Result:The response time of the two groups of subjects became quick with the reduction of the cue scale, while the amplitudes of P1 and N1 components of event-related potentials increased. Old subjects showed longer response time than young subjects, and the posterior P1 component was enhanced significantly and N1 component was inhibited obviously.The P2 component was manifested as significantly inhibitory effect not only in the amplitude but also in the abnormal and unstable waveform. Conclusion: Elderly subjects need consume more resources with increasing task complexity, which was in accordance with age -related complexity effect. We demonstrated for the first time that the P2 component was manifested as significantly inhibitory effect,which indicated that the elderly subjects showed decline in the cognitive research to target stimuli and suggested that the age-related changes could lead to deficit in the posterior area of the brain in visual spatial attention (voluntary attention).