基于N2pc成分的视觉空间注意功能老化机制

Aging Mechanism of Visual Spatial Attention—Evidence from N2pc Component

视觉空间注意是人的一种基本认知功能,对老年人的生活有重要影响。N2pc作为一种与注意选择相关的ERP成分,可以反映注意资源在空间上的分配,是研究视觉空间注意的一个良好指标。本文对此前基于N2pc成分的注意功能老化研究进行了综述。前人研究主要采用视觉搜索范式与空间线索范式。采用视觉搜索范式的研究发现,当目标周围有干扰子时,目标诱发的N2pc在老年人中振幅减小,潜伏期延迟,同时在行为上老年人与年轻人相比,正确率更低,反应时更长;当目标周围无干扰子时,目标诱发的N2pc振幅老年人与年轻人相当或比年轻人更大,老年人的正确率与年轻人无显著差异。采用空间线索范式的研究发现,与目标无相同特征的线索奇异子(singleton cue)不会诱发N2pc,与目标有相同特征的线索奇异子诱发的N2pc未表现出年龄差异,差异体现在一种反映抑制的ERP成分—Pd上(年轻人有Pd而老年人没有),此时老年人在行为上表现出比年轻人更强的空间线索效应。这些研究共同说明,视觉空间注意功能的老化是一个复杂的过程,涉及到搜索目标时注意分配速度的减慢,对干扰子抑制能力的下降以及基于特征的注意捕获能力的良好保持。

Visual spatial attention is a basic cognitive function in humans and plays an important role in daily life of older adults.As an ERP component related to attentional selection,the N2pc has been adopted as an index for deployment of visual spatial attention in numerous studies.This article provides an overview of previous studies about aging of visual spatial attention based on N2pc component.These studies usually used visual search paradigms or spatial cuing paradigms.The studies of visual search paradigms showed that,when there were distractors around targets,target-elicited N2pc was smaller and later in the elderly than in the young;meanwhile,the elderly showed lower accuracies and longer reaction times compared to the young.However,when there were no distractors around targets,the amplitude of target-elicited N2pc in the elderly was equal to,or even larger than in the young,reflecting that older adults may consume more attention resources in order to perform as good as the young adults.In studies of spatial cuing paradigms,no cue-elicited N2pc was observed when the cues did not possess target-relevant features,while there seemed to be no difference between the young and the old in cue-elicited N2pc when the cues possessed target-relevant features.The difference of ERP between the young and the older adults appeared in the Pd component(i.e.older adults did not show Pd while young adults did),which was considered to reflect the inhibition process.Meanwhile,the behavioral cuing effect was larger in the old than in the young.All these results together indicate that aging of visual spatial attention is a complex psychological process,involving slower deployment of attention resource when searching for targets,severe impairment in distractor inhibition,but good preservation in feature-based attentional capture.