Developmental dyslexia: specific phonological deficit or general sensorimotor dysfunction?

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*9. Nicolson RI, Fawcett AJ, Dean P: Dyslexia, development and the cerebellum. Trends Neurosci 2001, 24:515-516.

The latest and most comprehensive description of the cerebellar theory of dyslexia.

*10. Stein J: The magnocellular theory of developmental dyslexia. Dyslexia 2001, 7:12-36.

The latest and most comprehensive description of the magnocellular theory of dyslexia.

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**18. Share DL, Jorm AF, MacLean R, Matthews R: Temporal processing and reading disability. Reading and Writing: An Interdisciplinary Journal 2002, 15:151-178.

This is a unique longitudinal evaluation of the auditory temporal processing hypothesis. The authors have examined the relationship between auditory (Tallal's repetition test), phonological and reading skills from kindergarten to Grade 2. They have found that dyslexic children tended to have impaired auditory processing at long rather than short inter-stimulus intervals, and only compared to the chronological-age control group; and that early auditory deficits did not predict later phonological and reading impairments.

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**20. Chiappe P, Stringer R, Siegel LS, Stanovich KE: Why the timing deficit hypothesis does not explain reading disability in adults. Reading and Writing 2002, 15:73-107.

This is one of a few studies addressing the temporal processing hypothesis in the visual, auditory and motor domains within the same subjects, and with systematic manipulation of inter-stimulus intervals. It reveals that while dyslexics are often impaired at temporal processing tasks, there is no interaction with interval duration. And temporal processing skills do not predict phonological skills.

21. France SJ, Rosner BS, Hansen PC, Calvin C, Talcott JB, Richardson AJ, Stein JF: Auditory frequency discrimination in adult developmental dyslexics. Percept Psychophys 2002, 64:169-179.

**22. Amitay S, Ben-Yehudah G, Banai K, Ahissar M: Disabled readers suffer from visual and auditory impairments but not from a specific magnocellular deficit. Brain 2002, 125:2272-2285.

The authors have administered possibly the most comprehensive battery of visual psychophysical tests to date (and a few auditory tests) to adult dyslexics and controls. They have found that only a subset of dyslexics were impaired in these tasks, and not in the spatio-temporal range of frequencies predicted by the magno-cellular and temporal processing theories.

**23. Amitay S, Ahissar M, Nelken I: Auditory processing deficits in reading disabled adults. J Assoc Res Otolaryngol 2002, 3:302-320.

This is the most comprehensive study of dyslexic's basic auditory processing to date. It shows that a subgroup of dyslexics have an auditory deficit, but that it cannot be characterised in terms of rapid temporal processing. Furthermore, auditory skill does not predict reading skill, but seems to place an upper limit on it (poor listeners are poor readers, but not necessarily the other way around; a result quite similar to [31]).

24. van Ingelghem M, van Wieringen A, Wouters J, Vandenbussche E, Onghena P, Ghesquière P: Psychophysical evidence for a general temporal processing deficit in children with dyslexia. Neuroreport 2001, 12:3603-3607.

*25. Kronbichler M, Hutzler F, Wimmer H: Dyslexia: Verbal impairments in the absence of magnocellular impairments. Neuroreport 2002, 13:617-620.

Another rare study looking simultaneously at auditory, visual, motor and phonological skills in dyslexic children. The authors report no significant group differences in any of the sensorimotor tasks, yet large differences in phonological skill.

26. Witton C, Stein JF, Stoodley CJ, Rosner BS, Talcott JB: Separate Influences of Acoustic AM and FM Sensitivity on the Phonological Decoding Skills of Impaired and Normal Readers. J Cogn Neurosci 2002, 14:866-874.

27. Goswami U, Thomson J, Richardson U, Stainthorp R, Hughes D, Rosen S, Scott SK: Amplitude envelope onsets and developmental dyslexia: A new hypothesis. Proc Natl Acad Sci U S A 2002, 99:10911-10916.

28. Breier JI, Gray L, Fletcher JM, Diehl RL, Klaas P, Foorman BR, Molis MR: Perception of voice and tone onset time continua in children with dyslexia with and without attention deficit/hyperactivity disorder. J Exp Child Psychol 2001, 80:245-270.

*29. Serniclaes W, Sprenger-Charolles L, Carré R, Démonet J-F: Perceptual discrimination of speech sounds in developmental dyslexia. Journal of Speech, Language and Hearing Research 2001, 44:384-399.

A clever study comparing syllable discrimination within and across phonemic boundaries, and finding that dyslexics have, on average, better discriminative abilities within-boundaries, which would suggest that their perception is less categorical and more based on purely acoustic cues. The use of sine-wave speech allows the authors to tap speech and non-speech modes with the same stimuli: they find that enhanced within-boundary discrimination is stronger in speech mode, precluding an explanation in terms of temporal processing (this replicates [37] and is similar to findings by [30] and [31]).

*30. Rosen S, Manganari E: Is there a relationship between speech and nonspeech auditory processing in children with dyslexia? J Speech Lang Hear Res 2001, 44:720-736.

The authors have administered a large battery of speech and non-speech perceptual tests to dyslexic and control children. They show that speech perception skills are not predicted by non-speech perception skills, and that the perceptual deficits found in a subset of dyslexics cannot be explained in terms of rapid temporal processing.

**31. Ramus F, Rosen S, Dakin SC, Day BL, Castellote JM, White S, Frith U: Theories of developmental dyslexia: Insights from a multiple case study of dyslexic adults. Brain in press.

This study describes possibly the largest battery of phonological, auditory, visual and cerebellar/motor tests administered to dyslexics and controls. It reports a very limited incidence of visual and motor deficits. Auditory deficits are present in 60% of the dyslexic sample, but with very variable manifestations across individuals (not particularly rapid processing) and at most an aggravating influence on the phonological deficit. Every single dyslexic in this sample shows a phonological deficit, with a third of them who seem entirely spared by any concurrent sensory or motor deficit.

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40. Kujala T, Karma K, Ceponiene R, Belitz S, Turkkila P, Tervaniemi M, Näätänen R: Plastic neural changes and reading improvement caused by audiovisual training in reading-impaired children. Proc Natl Acad Sci U S A 2001, 98:10509-10514.

*41. Friel-Patti S, Frome Loeb D, Gillam RB: Looking ahead: An introduction to five exploratory studies of Fast Forword. American Journal of Speech-Language Pathology 2001, 10:195-202.

*42. Gillam RB, Frome Loeb D, Friel-Patti S: Looking back: A summary of five exploratory studies of Fast Forword. American Journal of Speech-Language Pathology 2001, 10:269-273.

These two papers introduce and summarise a "Special forum on Fast ForWord" including five small-scale independent assessments of the controversial remediation program [39]. The first paper recalls all the important issues concerning the proper evaluation of remediation programs in general and that of Fast ForWord in particular (NB: they also apply to [40]). The second paper concludes that Fast ForWord does not seem more effective than other more conventional remediation programs.

*43. Hook PE, Macaruso P, Jones S: Efficacy of Fast ForWord Training on Facilitating Acquisition of Reading Skills by Children with Reading Difficulties - A Longitudinal Study. Annals of Dyslexia 2001, LI:75-96.

In this study the effectiveness of the Fast ForWord program was compared to the (less intensive) Orton Gillingham training in two matched groups of reading-disabled children. Overall, the authors found very similar (positive) outcomes for the two programs, and question the specific role played by acoustically modified speech.

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48. Hari R, Renvall H, Tanskanen T: Left minineglect in dyslexic adults. Brain 2001, 124:1373-1380.

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50. Davis C, Castles A, McAnally K, Gray J: Lapses of concentration and dyslexic performance on the Ternus task. Cognition 2001, 81:B21-31.

51. Hansen PC, Stein JF, Orde SR, Winter JL, Talcott JB: Are dyslexics' visual deficits limited to measures of dorsal stream function? Neuroreport 2001, 12:1527-1530.

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*56. Olson R, Datta H: Visual-temporal processing in reading-disabled and normal twins. Reading and Writing 2002, 15:127-149.

This is the first behavioral-genetic study of visual magnocellular function, conducted on 356 twins. It found that reading-disabled twins had significantly higher contrast detection thresholds on average; however, this was found across all spatial and temporal frequencies. Moreover, there was no significant genetic influence on individual differences in threshold levels.

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