Reading processes and visual or surface «dyslexia» – part 2
Lexical or whole-word reading
Competent reading essentially involves the whole-word or lexical process of reading which ensures fluent reading and a "direct" access to meaning. It recognizes the shape of the word and immediately find its sound correspondence in memory (or phonological), the meaning of the word being evoked, which is the ultimate goal of reading.
The whole-word process (or eidetic = photographic), both more automatic and faster, can even bypass the phonological pathway, which is more controlled and slower. Most of the time, the expert reader would not need to use his phonological knowledge to recognize written words. The observation of a double dissociation between visual and phonological dyslexia in patients with brain damage is an argument in favor of the neuropsychological existence of the two independent procedures for the recognition of written words (Coltheart, Masterson, Byng, Prior & Riddoch, 1983; Funnell, 1983; Shelton & Weinrich, 1997). Numerous studies supporting these models have also emphasized the optional phonological code while reading (Peereman, 1991, for a review).
Coltheart M, Masterson J, Byng S, Prior M, Riddoch J. Surface dyslexia. Q J Exp Psychol A. 1983 Aug;35(Pt 3):469-95.
Funnell E. Phonological processes in reading: new evidence from acquired dyslexia. Br J Psychol. 1983 May;74 (Pt 2):159-80.
Weinrich M, Shelton JR, McCall D, Cox DM. Generalization from single sentence to multisentence production in severely aphasic patients. Brain Lang. 1997 Jun 15;58(2):327-52.
Peereman R. Phonological assembly in reading: lexical contribution leads to violation of graphophonological rules. Mem Cognit. 1991 Nov;19(6):568-78.
When the child becomes able to recognize a word as a unit, he gradually builds his orthographic lexicon. The operation of this lexicon is not yet fully known, but it seems to be like a dictionary which exists in our brain, allowing rapid identification (the faster the more familiar word) and immediate access to meaning.
This procedure then develops to become more and efficient as reading becomes more competent. Ultimately, the adult reader would only use the "photographic" procedure, which is obviously much faster than going through words syllable by syllable (which remains necessary when we must read for example, new or meaningless words or of a foreign language).
http://www.coridys.asso.fr/pages/base_doc/txt_habib/entree.html
Imagine a child who reads the following sentence:
"The locomotive arrives at the station"
"The-lo-co-mo-ti-ve-ar-ri-ves-at-the-sta-tion".
(or syllable by syllable)
In the first case, the child immediately recognizes the words and understands what he reads. In the second case, the child does not read words but syllables one by one. Difficult to quickly understand what is read.
Surface dyslexia
Surface dyslexia, in its pure form, is characterized by a selective impairment of reading irregular words while reading regular words and pseudo-words is relatively preserved. This selective difficulty reading irregular words translates a dysfunctionnal lexical reading procedure.
These children do not present associated disorders of oral language and have good capabilities in short term verbal and workong memory and have good phonological awareness. They also have difficulties in visual processing that make comparing sequences of letters or identify targets among others.
It is said that pure forms of surface dyslexia are relatively rare in clinical practice. But I can assure you that in my optometric practice, these children are much more numerous than the statistics show.
Visuo-attentional dyslexia
There is also, according to some authors, another form of dyslexia, called "visual-attentional" where the child has a good memory of the spelling of words and is able to transcribe sounds into words. For cons, the type of errors encountered in this disorder is reversals in groups of letters, omissions, additions, approximate reformulations, skippng lines while they read. line breaks. The child may confuse letters and words with others closely resembling it. It would be a disorder affecting necessary attention for an effcient reading activity.
(In : http://www.ac-grenoble.fr/ia73/spip/IMG/pdf/dys_apedys.pdf)
These children also have oculomotor (eye movement) and visual discrimination problems, difficulties in visual attention, difficulties in copying material from a book or the blackboard.
It is difficult to conceive a child who has a serious visuo-attentional problem would not show a form of surface dyslexia. There is certainly a very close relationship between the two since both can prevent the establishment of a proper orthographic lexicon. They may also be different manifestations of the same problem called "visual dyslexia". This close relationship between visual and attentional problems is reinforced by the significant progress in reading and spelling seen in a child with surface dyslexia following a trainign program focused on visual processing capabilities (Launay and Valdois , 1999)
Valdois S, Launay L. Évaluation et rééducation cognitives des dyslexies développementales: illustration à partir d'une étude de cas. In : La rééducation neuropsychologie : Études de cas. AZOUVI P, PERRIER D, VAN DER LINDEN M (eds). Marseille, Solcoll, 1999 : 95-116).
Visual-perceptual skills essential to insure adequate whole-word reading
It is probably unnecessary to say that the best readers are those who read in a whole-word fashion, this method of reading is fast and understanding is also much better. But what is the action to take if a child uses no or has a poor orthographic lexicon? We must ensure that the related visual and perceptual skills are adequate. Otherwise, visual training will be needed to improve these skills.
What are the skills that have a close relationship with the development of orthographic lexicon? First, eye movements: reading requires a constant movement of the eyes along a line of text, which is done by a series of short jumps (saccades) interspersed with longer breaks during which takes place all intake of visual information. These jumps between fixations are very short, about one-thirtieth of a second. Saccades take approximately 250 to 300ms. Saccades are also an index of visual attention. We have tests that evaluate the speed, accuracy and fluency of reading. Eye movement problems hamper efficient learning and reading quality (failure to follow the text, loss of place, jump words or lines, etc.). For reading to be effective, eye movements must be flexible, fast and accurate.
Then visual attention and concentration allow the child to remain focused and attentive to every detail of what we see and as long as necessary. Attention and concentration are a preqequisite to good visual discrimination. In addition, visual attention is the link between perception (making information available) and cognition (use this information). It ensures maximum reception all the information from our visual environment. Visual concentration promotes maximum use of working memory to collect, store, retrieve and process the relevant information. It facilitates the work and especially the intellectual performance.
Short-term and sequential visual memories allow the child to recognize an item after a brief exposure, or to recall items in the same order and in the same sequence. For example, remembering the order of letters in a word or words in a sentence with a quicker understanding of what is read. Children who show difficulties in visual sequential memory may have difficulties copying information from the board or a book, to learn to read mulriple words or sentences and remember what they read. They may also have difficulties in creating their orthographic lexicon, which affects fluency and reading comprehension.
Visualization or mental imagery is the ability to create images of a word, a sentence or a paragraph in our head (our mental picture). This ensures good understanding of what is read and allows a better organization of information, making it easier to retain and build an efficient orthographic lexicon. This perceptual skill is also essential for mental arithmetic and spelling of words. If a child reads a story without being able to mentally see the scene described in the text, then this will influence contextual
In summary, the eyes must move effectively to ensure high quality of visual information, and the child must be able to remain attentive and focused on what he reads. Visual memory will also allow to recognize the same words in a text. Many children can not build a orthographic lexicon because they can not even recognize a word they just read and read again a few lines later. Visualization allows the child to "juggle with words" in his head. And finally, it is practicing reading every day that ensures efficiency in reading. More often we see the same words, the faster they will be included in the orthographic lexicon.
According to scientific research, three basic skills (among others) will thus directly influence reading performance in children: visual memory, visual attention and visualization. The best readers are capable of recognizing whole words easily (eidetic, global or whole-word reading). This accelerates visual decoding, requires less energy and promotes better understanding. Reading phonologically (syllable by syllable) slows down the reading process and does not guarantee an adequate understanding of a text. The best readers need not phonological awareness to read and can recognize most words without having to dissect them. That is why we have developed a particular portion of our vision therapy to enhance these perceptual abilities. We try to develop better whole-word reading to improve reading efficiency and comprehension.
Dyslexia, Learning problems and vision, Optometry, Reading problems and vision, Vision
"True"dyslexia is seemingly a "neurological" dysfunction (of course, we read with our brain, not just the eyes!) marked by the inability of the brain centers to efficiently decode print or phonetically make the connection between written symbols and their appropriate sounds. The connotation of the word "neurological" can be confusing: this word is too easily understood or related to a nervous system disease. Dyslexia may be caused by a nervous system dysfonction, but surely not a disease!
The origin of this problem, yet ardently debated in the literature, is probably multi-causal. It is unfortunate that the researchers are constantly looking at only a small aspect of dyslexia in their studies. We also know that not all children who have difficulty reading, however, suffer from phonological processing. Although the symptoms are similar, they may also have visual and perceptual problems that interfere with adequate learning, not just a deficit-based language, as some would have us believe…
Margaret Livingstone, et al, from the Department of Neurobiology, Harvard Medical School and the Dyslexia Research Laboratory, Beth Israel Hospital in Boston reports that poor visual processing plays a significant role in a large majority of children who struggle to read: "Several perceptual studies have suggested that dyslexic subjects process visual information more slowly than normal subjects. Such visual abnormalities were reported to be found in more than 75% of the reading-disabled children tested."
Livingstone MS, Rosen GD, Drislane FW, et al. Physiological and anatomical evidence for a magnocellular defect in developmental dyslexia. Proc Natl Acad Sci USA 1991; 88:7943-7.
Moreover, all children with learning difficulties in primary school are not dyslexic, and vice versa, a child may be dyslexic without it being prolonged failure (especially if dyslexia is mild and if it can be compensated by the development of other skills intact).
Essentially, there is also a problem in the clinical definition of dyslexia. Everyone has their own definition and tests used in the diagnosis of such a condition do not always lead to a clear diagnosis… This imprecision in diagnosis can also certainly explain the variability in prevalence rates reported in the literature (this rate may actually increase from 4% (Yule and Rutter, 1973) to 20% (Shaywitz, 1996)).
Yule W, Rutter M, Berger M, Thompson J. Over- and under-achievement in reading: distribution in the general population. Br J Educ Psychol. 1974 Feb;44(1):1-12.
Shaywitz SE. Dyslexia. Sci Am. 1996 Nov;275(5):98-104.
A child in early primary school may have some difficulty learning to read, this situation is common and there is no question of going overboard and put a label of "dyslexia" for all these children.
Decoding process of reading: the dual-route model
The dual-route model is very frequently used as a reference model for decoding during reading. This model postulates the existence of two procedures involved in both reading and writing.
Dual-route reading process
From : http://www.cognisciences.com: Outil de Dépistage des Dyslexies – Odedys2 – 2009
Phonological process
The phonological process is characterized by a sequential analytical processing or syllabic of a word or pseudo-word (invented word). It involves a system of rules for grapheme (a letter or two, sometimes three) – phoneme (sound related) explicitly learned in school.
The word "camel" when processed through this system will be segmented into graphemes <CA – MEL>, then each grapheme will be assigned to a phoneme which is most frequently associated in the language This allows to generate the sequence of the word.
Only the phonological process allows the processing of new words (words not previously learned or "pseudo-words" which are words invented for the purposes of experiment, for example: famsled, posvent or rolted).
Insofar as the treatment of new words is dedicated to this system, lists of pseudo-words are systematically tested for reading and dictation for children with difficulties, to test the integrity of the phonological process. Good performance in reading invented words indicates that the phonological process is operational, poor performance involves an inadequacy of this pathway.
It is known that the analytical (phonological) route plays a major role in early learning as it is chronologically the first. If we conceive that in adults both channels are relatively autonomous, it seems unlikely that these two pathways are also distinct in children who are learning to read.
Whole-word or eidetic process
The lexical procedure (or whole-word process) performs simultaneous processing of all the elements of the word. All units which compose the word are processed in parallel, leading to the activation of the orthographic lexicon stored in the brain and learned previously. The child sees the word and understands it immediately.
In reading, and after some visual processing, the representation of the word as a whole is activated in our orthographic lexicon (the "dictionary within our head") and gives a very rapid access to the sound structure (phonology) corresponding to this word and its meaning. No need to decode the word syllable by syllable.
The way this lexicon functions is not yet fully known, but it seems to be like a dictionary to which we would refer for each word read, according to a "photographic" procedure, allowing rapid identification (the faster the more familiar is the word) and immediate access to meaning.
Each of the two procedures for reading (or writing) is implemented specifically for the treatment of certain types of words: the lexical route or process can only deal with words already learned and whose representations are available within the orthographic lexicon and its phonological correspondence. It is needed when reading or writing irregular words that are not pronounced the way they are written (for example, rough, soared, laugh). Irregular words that can only be handled by the lexical route is used in the evaluation of children with learning disabilities. Lists of irregular words are proposed or presented to test the integrity of the lexical route: a good performance when reading these words shows that the lexical procedure is operational; poor performance in reading irregular words compared to reading regular words or pseudo-words suggests a failure of the lexical procedure.
(Part 2 in next blog)