Universite de Montreal and Institut Universitaire de Geriatrie de Montreal, Canada.
Cogn Neuropsychol. 2006;23(2):240-60. doi: 10.1080/02643290442000437.
Two critical issues were examined regarding letter-by-letter (LBL) dyslexia: (1) What is the nature of the functional impairment responsible for the incapacity of LBL patients to overtly recognise words on the sole basis of parallel letter processing? (2) What is the purpose of sequential letter processing? Four experiments focusing on these issues were conducted in LH, an LBL dyslexic. Expt 1 showed facilitatory effects of increased phonographic neighbourhood size, lexical frequency, and imageability on the word naming performance of LH. These high-order effects reflect a modulation of parallel letter processing in LH and demonstrate that he is able to rapidly access phonological, lexical, and semantic knowledge during reading. Congruently, Expt 2 demonstrated that all three high-order effects are eliminated when words are presented one letter at a time, from left to right. Expt 3 showed that these high-level effects are also abolished if target words are made of letters that are highly confusable (i.e., visually similar) to other letters of the alphabet. These observations suggest that LBL dyslexia may rest on an impairment at the letter encoding level that causes an excessive level of background noise in the activation of higher-order representations (i.e., letter combinations) when letters are processed in parallel. An additional experiment (Expt 4) shows that the letter confusability effect is also eliminated when words are presented one letter at a time, from left to right. This latter finding suggests that compensatory sequential processing invoked by LBL dyslexics serves to avoid the confusion between visually similar letters, which is present with parallel letter processing, and to amplify the signal-to-noise ratio required to achieve overt word identification.
两个关键问题被检查了关于逐字母（LBL）失读症：（1）是什么的功能损伤负责的无能的 LBL 患者公开地认出词根据平行字母处理？（2）是什么目的的顺序字母处理？四个实验集中在这些问题进行了在 LH，一个 LBL 失读症。实验 1 表明促进效果增加了 phonographic 邻里的大小，词汇频率和形象，在词命名性能的 LH。这些高阶效应反映了调制的平行字母处理的 LH 和证明他能够迅速获得语音，词汇和语义知识在阅读过程中。一致地，实验 2 表明，所有三个高阶效应都被消除时，单词一次一个字母呈现，从左到右。实验 3 表明，这些高层次的影响也被取消，如果目标词是由字母，这是非常混淆（即，视觉上相似）到其他字母的字母表。这些观察表明，LBL 失读症可能基于一个损伤的字母编码水平，导致过度水平的背景噪声在激活的高层次的代表（即，字母组合），当字母处理的平行。一个额外的实验（实验 4）表明，字母混淆效应也被消除时，单词一次一个字母呈现，从左到右。这后一个发现表明，补偿顺序处理调用的 LBL 失读症服务，以避免混淆之间的视觉相似的字母，这是目前与平行字母处理，并放大信号噪声比需要实现明显的单词识别。
