文字加工专家化的老化效应研究—来自ERP 的证据

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	文字加工专家化的老化效应研究—来自ERP 的证据
其他题名	Aging effects on neural specialization of visual word processing: An ERP Study
	唐慧君
	2015-05
摘要	神经影像研究发现大脑左侧枕颞后部区域对文字具有选择性反应，这一区域被称为视觉词形加工区（visual word form area, VWFA）。电生理研究发现在文字刺激呈现后约 200毫秒，左侧枕颞区可以观测到明显的 N170反应，VWFA可能就是 N170 的源。这种文字诱发的左侧化 N170 被认为是文字加工专家化的电生理标志。文字加工专家化的出现与形成经历了一个从出现神经粗糙调谐到出现神经精细调谐的发展过程，表现出受阅读经验影响的特点。现有研究已考察了从儿童到青少年再到成年人文字加工 N170的发展过程及其特点。那么，随着年龄进一步增加、阅读经验日趋丰富，特别是在进入老年期，人的大脑和认知功能出现老化时，文字加工专家化 N170会表现出什么样的特点呢？对这个问题目前所知甚少。但大量有关记忆、面孔知觉等方面的老化研究发现，老年人在完成认知任务时其大脑活动表现出神经反应类别选择性减小及半球活动偏侧化减小两个显著的特点。针对上述问题，本研究采用ERPs 技术，从神经粗糙调谐和精细调谐两个层面考察老年人在加工汉字及其它类别视觉刺激时的早期大脑活动特点。研究选取60-79 岁的老年被试并以在校大学生被试作为对照组。研究内容主要包括：（1）在粗糙调谐层面，考察老年人加工文字时是否会表现出神经反应类别选择会减小，同时考察老年人文字加工左侧化 N170是否会出现偏侧化减小。（2）在精细调谐层面，考察老年人加工不同正字法层次的视觉刺激所诱发的神经反应类别选择性是否会减小，同时考察老年人加工不同正字法层次的刺激时 N170偏侧化的变化情况。研究主要分析两组被试大脑枕颞区 P1 和 N170 的波幅、潜伏期以及相关的行为反应（反应时和正确率）。主要研究结果如下： 1. 与年轻被试类似，老年人文字加工的 N170波幅显著高于物体等对照刺激，文字加工的 N170波幅在具有不同正字法特征的视觉刺激间出现了很好地分化，说明老年人对文字的神经粗糙调谐与精细调谐几乎都没有受到老化的影响。 2. 老年人文字加工表现出枕颞区 N170活动偏侧化减小，说明老年人通过征用对侧半球相应区域来弥补大脑老化所引起的认知功能衰退。 3. 老年人枕颞区P1、N170波幅比年轻人强，这可能反映了老年人在知觉早期阶段就开始动用了比年轻人更多的认知资源。
其他摘要	Neuroimaging studies have identified a region, visual word form area (VWFA), in the left mid-fusiform cortex, specialized for visual word processing. In parallel, electrophysiology studies have revealed a word-related negative event-related potential component (N170, around 200 ms after the onset of stimuli) over the left occipital-temporal area. Recent studies from different scripts further show that the left-lateralized N170 is an index of neural specialization for visual words processing regardless of script types. The emergence and development of this neural specialization for visual word processing undergoes a process from early coarse tuning to late fine tuning; both are mainly driven by reading experiences. While there are a large number of studies investigating the development of the N170 response for visual words in children, little is known about changes in the neural specialization for visual words processing, from a life-span developmental perspective, particularly changes with aging. Numerous studies on aging effects in memory and face processing suggest that there are two types of brain activity changes in older adults – one is less neural selectivity, and another is hemispheric asymmetry reduction. However, no empirical evidence has yet been provided for aging-related changes in the neural specialization for visual words. In the present study, we aimed to fill in this gap and investigate the aging effects on Chinese character processing using ERPs. We compared 60-79 years old adults and college students, to address two questions: (1) whether there exits less neural selectivity and/or hemispheric asymmetry reduction when older adults processing Chinese characters and other category stimuli, such as common objects; (2) whether there exits less neural selectivity and/or hemispheric asymmetry reduction when older adults processing character/character-like stimuli with different levels of orthographic regularity. We analyzed P1 amplitudes and latencies at sites O1/O2 and N170 amplitudes and latencies at sitesT5/T6. Behavioral response time and accuracy were recorded and analyzed as well. The main findings of this thesis are as follows: 1. Similar to young adults, the amplitudes of N170 to Chinese characters were stronger than those to control stimuli, and the amplitudes of N170 to orthographic stimuli were stronger than those to non-orthographic stimuli in older adults. These results suggest that coarse tuning and fine tuning for Chinese characters do not change significantly with aging. 2. Older adults were characterized by hemispheric asymmetry reduction of N170 response to Chinese characters, suggesting that the older adults may recruit contra-lateral regions to recognize visual words for compensating their neurocognitive deficits, unlike in young adults, reading is basically involved with the left hemisphere. 3. The amplitudes of P1 and N170 of the visual stimuli were stronger in older group than that in young group, suggesting that older adults need more cognitive resources during processing visual stimuli.
学科领域	认知神经科学
关键词	文字加工专家化老化效应 N170 ERP
学位类型	博士
语种	中文
学位专业	心理学
学位授予单位	中国科学院研究生院
学位授予地点	北京
文献类型	学位论文
条目标识符	http://ir.psych.ac.cn/handle/311026/19661
专题	认知与发展心理学研究室
作者单位	中国科学院心理研究所
推荐引用方式 GB/T 7714	唐慧君. 文字加工专家化的老化效应研究—来自ERP 的证据[D]. 北京. 中国科学院研究生院,2015.

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