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Using both PET and fMRI, Paulescu et al. 2001, show that dyslexia in alphabet writing systems has a universal basis in the brain and can be characterized by the same neurocognitive deficit. Clearly, the manifestation in reading behavior is less severe in a shallow orthography. However, our results show that if more sensitive tests were available, the neurocognitive deficit would be detected. Although Italians with dyslexia read more accurately than French or English people with dyslexia, they showed the same degree of impairment on reading latencies and reading-related phonological tasks relative to their controls. They conclude that a phonological processing deficit is a universal problem in dyslexia and causes literacy problems in both shallow and deep orthographies. However, in languages with shallow orthography, such as Italian, the impact is less, and dyslexia has a more hidden existence. By contrast, deep orthographies like that of English and French may aggravate the literacy impairments of otherwise mild cases of dyslexia.

A study comparing children's reading acquisition rates between different orthography of European Language (alphabet writing systems), Seymour et al. 2003, found that children from a majority of European countries become accurate and fluent in foundation level reading before the end of the first school year. There are some exceptions, notably in French, Portuguese, Danish, and, particularly, in English. The effects appear not to be attributable to differences in age of starting or letter knowledge. It is argued that fundamental linguistic differences in syllabic complexity and orthographic depth are responsible. Syllabic complexity selectively affects decoding, whereas orthographic depth affects both word reading and non-word reading. The rate of development in English is more than twice as slow as in the shallow orthographies. It is hypothesized that the deeper orthographies induce the implementation of a dual (logographic + alphabetic) foundation which takes more than twice as long to establish as the single foundation required for the learning of a shallow orthography.

logographic dyslexia

Although alphabetic dyslexia seems to originate in the left temporoparietal and occipitotemporal areas of the brain, recent studies indicate that logographic dyslexia is associated with part of the left middle frontal gyrus. This suggests that "the structural and functional basis for dyslexia varies between alphabetic and nonalphabetic languages.

FULL ABSTRACT

Developmental dyslexia is a neurobiologically based disorder that affects ≈5–17% of school children and is characterized by a severe impairment in reading skill acquisition. For readers of alphabetic (e.g., English) languages, recent neuroimaging studies have demonstrated that dyslexia is associated with weak reading-related activity in left temporoparietal and occipitotemporal regions, and this activity difference may reflect reductions in gray matter volume in these areas. Here, we find different structural and functional abnormalities in dyslexic readers of Chinese, a nonalphabetic language. Compared with normally developing controls, children with impaired reading in logographic Chinese exhibited reduced gray matter volume in a left middle frontal gyrus region previously shown to be important for Chinese reading and writing. Using functional MRI to study language-related activation of cortical regions in dyslexics, we found reduced activation in this same left middle frontal gyrus region in Chinese dyslexics versus controls, and there was a significant correlation between gray matter volume and activation in the language task in this same area. By contrast, Chinese dyslexics did not show functional or structural (i.e., volumetric gray matter) differences from normal subjects in the more posterior brain systems that have been shown to be abnormal in alphabetic-language dyslexics. The results suggest that the structural and functional basis for dyslexia varies between alphabetic and nonalphabetic languages.

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In other words, alphabetic and logographic dyslexia are most likely separate disorders; a person with alphabetic dyslexia would not necessarily also have logographic dyslexia, and vice versa.

The distinction between these two forms of dyslexia has led to promising therapeutic research. One study led by Alberto Sáez-Rodríguez discovered that syllabic logograms could act as a learning aid to alphabetic-dyslexic English-speaking children.

Syllabic Writing

Syllabaries often begin as simplified logograms, as shown here with the Japanese katakana writing system. To the left is the modern letter, with its original Chinese form on the right.

A syllabary is a set of written symbols that represent (or approximate) syllables, which make up words. A symbol in a syllabary typically represents an optional consonant sound followed by a vowel sound.

Languages using syllabaries

Languages that use syllabic writing include Mycenaean Greek (Linear B), the Native American language Cherokee, the African language Vai, the English-based creole language Ndyuka (the Afaka script), and Yi language in China. Nü Shu is a syllabary that was used to write the language of the Yao people in China. The Chinese, Cuneiform, and Maya scripts are largely syllabic in nature, although based on logograms. They are therefore sometimes referred to as logosyllabic. The Japanese language uses two syllabaries together called kana, namely hiragana and katakana (developed around AD 700). They are mainly used to write some native words and grammatical elements, as well as foreign words, e.g. hotel is written with three kana, ホテル (ho-te-ru), in Japanese. Because Japanese uses many CV (consonant + vowel) syllables, a syllabary is well suited to write the language. As in many syllabaries, however, vowel sequences and final consonants are written with separate glyphs, so that both atta and kaita are written with three kana: あった (a-t-ta) and かいた (ka-i-ta). It is therefore sometimes called a moraic writing system.