范围提示下视空间注意老龄化的事件相关电位研究

Study of event-related potential on the visual attention of aging under region cues

目的采用“提示-目标”的视觉实验模式,以范围提示不同等级的搜索范围,通过事件相关电位(ERP)技术,研究视觉注意老龄化脑机制。方法用青年人和老年人各16名为健康受试者,背景由3个同心黑色圆形线条组成,提示为大、中、小不等的3个圆圈组成,刺激材料是随机选取的大写英文字母,组成3个同心圆圈。当大圈提示时,靶刺激 T 可出现在3个圈;中圈提示时,靶刺激 T 出现在中和小圈;当小圈提示时,靶刺激 T 出现在小圈。结果随着提示等级的增大,两组反应时均逐渐延长,早期 ERP 成分 P1与 N1波幅均减小,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 P2成分受到显著抑制,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。结论老年组 ERP 的 P2成分显著抑制,表明老年人对靶刺激的评估识别能力降低,提示可能导致视觉空间注意(非随意注意)的前脑区功能缺陷。

Objective To investigate the brain mechanisms of aging of the visual attention. Methods Through the precue-target visual search paradigm using the event-related potentials technique,16 young and 16 elderly subjects participated the electrophysiological experiment. The background was comprised of three homocentric black circles and eight English capital letters consisted of each circle. The letter ＂T＂ was designed as the target stimulus. T was a target only when it located the circle clued to the same size of the precue. For example, when the cue was the ＂large＂, ＂T＂ may appear within 3 circles. When the cue was the ＂median＂, ＂T＂ may appear within either the median or small circles. When the cue was small, the target ＂T＂ may appear only within the small circle. Results The reaction 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 with the decrease of the cue scale. Old subjects showed longer response time than did 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. Conclusions The cognitive function of elderly subjects declines in the research of target stimuli ,which suggests that the age-related changes could lead to deficit in the posterior area of the brain to visual spatial attention （involuntary attention）.