Pioneering a New Method for Investigating the Neural Correlates of Ageing Effects during Natural Reading

阅读对于人们在现代社会中有效地发挥作用至关重要。此外，良好的阅读能力对社会包容很重要，而且往往对个人高效工作、获得教育机会和获得新技能至关重要。然而，大量研究表明，与年轻人(18-30岁)相比，老年人(65岁以上)即使在视觉和智力能力正常的情况下，也会遇到相当大的阅读困难。令人惊讶的是，人们对这种与年龄相关的阅读困难的根本原因或如何克服知之甚少。然而，随着人口老龄化以及老年人工作寿命延长的可能性增加，老年人在社会中的比例增加，这一问题可能会变得越来越重要，因为他们往往从事需要良好阅读能力的工作。因此，对衰老对阅读的影响进行科学研究是非常重要的。当我们阅读时，我们的眼睛在一系列的高速跳跃(眼跳)中运动，中间隔着大约四分之一秒的短暂停顿(凝视)。在每一次注视过程中，读者在视觉和语言上处理一小部分文本，然后进行扫视来检查新的部分。对这些眼球运动的定量测量一直是研究自然阅读的首选方法，并导致了管理这种行为的心理过程的详细理论模型的发展，包括这些过程如何随着年龄的变化而变化。然而，这种方法的一个主要局限性是，眼球运动不能直接提供关于潜在大脑过程的信息，尽管如果我们要更充分地了解衰老对阅读行为影响的基本机制，这种知识是必不可少的。我们的项目通过开创一种新的方法来解决这个问题，这种方法允许在自然阅读过程中实时检查大脑过程。这是通过使用高精度眼睛跟踪器同时记录眼睛运动和放置在头皮上的电极对大脑活动的脑电(EEG)测量来实现的。然后我们同步这些信号，以便脑电记录被时间锁定到句子中特定单词的单个注视，从而使我们能够量化在视觉处理这些单词时发生的大脑活动模式。一旦平均(在实验中经过多次试验)，得到的脑电记录(与注视相关的脑电位，或FRP)显示出典型的波形，其中包含对影响单词识别的因素选择性敏感的成分(峰和谷)。联合配准方法很难实现。因此，我们的第一个目标是证明在老年参与者中使用这种方法的可行性。然后，我们建议进行三个实验，以确定这种新方法在揭示自然阅读过程中单词识别的年龄差异方面的实用性。为此，我们将评估年龄对阅读过程中影响单词识别的两个关键因素的影响。第一个是单词的书面使用频率(以及读者对它的熟悉程度)，第二个是一个单词从它之前的句子上下文中的可预测性。对衰老效应的理论解释预测，由于老年人的词汇处理速度较慢，对上下文的依赖程度更高，因此老年人的词频和词汇可预测性都比年轻人更大。因此，重要的是要确定我们的新方法是否能检测到这些因素对阅读过程中大脑过程的影响的年龄差异。这个项目存在很大程度的风险。但如果我们取得了成功，我们正在开创的方法很可能会在心理学研究中产生范式转变，研究衰老对视觉认知(包括阅读)的影响，提供工具来开发新的理论，并获得关于大脑过程的新证据，这些过程是构成社会重要日常功能的基础。

Reading is vital for people to function effectively in modern societies. Furthermore, good reading abilities are important for social inclusion and often essential for individuals to work productively, access educational opportunities and acquire new skills. However, numerous studies show that, compared to young adults (aged 18-30 years), older adults (aged 65+ years) experience considerable difficulty reading even when their visual and mental abilities appear normal. Surprisingly little is known about the underlying cause of this age-related reading difficulty or how it might be combated. However, this issue is likely to be increasingly socially important as the proportion of older people in society increase due to population ageing, as well as the likelihood that they will have extended working lives, often in jobs requiring good reading abilities. Scientific investigations of ageing effects on reading are therefore very important.When we read, our eyes move in a series of high-velocity jumps (saccades) separated by brief pauses (fixations) lasting about a quarter of a second. Readers visually and linguistically process a small portion of text during each fixation, before making a saccade to inspect a new portion. Quantitative measures of these eye movements have been the preferred way to study natural reading, and led to the development of detailed theoretical models of the mental processes that govern this behaviour, including how these might change with age. However, a major limitation of this approach is that eye movements are not directly informative about underlying brain processes, although such knowledge is essential if we are to more fully understand the fundamental mechanisms responsible for ageing effects on reading behaviour.Our project addresses this issue by pioneering a new method that permits the examination of brain processes in real-time during natural reading. This is achieved by simultaneously recording eye movements using a high-precision eye-tracker and electroencephalographic (EEG) measures of brain activity from electrodes placed on the scalp. We then synchronise these signals so that the EEG record is time-locked to individual fixations on specific words in sentences, thereby allowing us to quantify patterns of brain activity that take place as these words are processed visually. Once averaged (over trials in an experiment), the resulting EEG recording (the fixation-related brain potential, or FRP) exhibits a stereotypical waveform with components (peaks and troughs) that are selectively sensitive to factors that influence a word's recognition.The co-registration method is difficult to implement. Our first objective, therefore, is to demonstrate the viability of using this method with older adult participants. We propose then to conduct three experiments to establish the utility of this new method for revealing age differences in word recognition during natural reading. To do this, we will assess ageing effects on two key factors that affect word recognition during reading. The first is the frequency of a word's written usage (and so its familiarity to readers), and the second is the predictability of a word from its prior sentence context. Theoretical accounts of ageing effects predict larger effects of both word frequency and word predictability for older than young adults, due to slower lexical processing and greater reliance on context in older age. It will be important, therefore, to establish if our new method can detect age differences in the influence of these factors on brain processes during reading. There is a significant degree of risk to this project. But if we are successful, the approach we are pioneering is likely to produce a paradigm shift in psychological research on ageing effects on visual cognition (including reading) by providing the tools to develop new theories and obtain new evidence about brain processes that underlie socially-important everyday functions.