**4. Literature relevant to the visual and visual-attentional sides of 'The Tales of Jud the Rat' reading fluency programme**

### **4.1. Rapid visual and auditory processing as predictors of reading difficulty**

A number of studies have indicated that developmental dyslexics do poorly in tests requiring rapid visual and auditory processing. Witton et al. [111] reported that neuronal mechanisms that were specialised for detecting stimulus timing and change were dysfunctional in many dyslexic individuals. The dissociation observed in the performance of dyslexic individuals on different auditory tasks also suggested a sub-modality division in the auditory system similar to that already described in the visual system.

Both Farmer and Klein [112] and Stein and Walsh [113] reported that dyslexia was associated with difficulties with moving visual stimuli. Hari and Renvall [114] also reported that dyslexic subjects often suffered from impaired processing of rapid stimulus sequences and suggest that sluggish attentional shifting can account for the impaired processing of rapid stimulus sequences in dyslexia. Amitay et al. [115] concluded that disabled readers suffered from both visual and auditory impairments, showing impaired performance in both visual and auditory tasks requiring fine frequency discriminations.

Talcott et al. [116] reported that both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills. Cohen-Mimran and Sapir [117] reported auditory temporal processing deficits in children with reading disabilities, and that children with reading difficulties had difficulty in discriminating between pure tones with short, but not long, interstimulus intervals, whereas controls performed well with both short and long interstimulus intervals.

Rapid auditory processing deficits have also been found to be consistent predictors of later reading achievement [118]. Lervåg and Hulme [119] reported that rapid automatised naming (RAN) measured with non-alphabetic stimuli before reading instruction had begun was a predictor of later growth in reading fluency, and continued to exert an influence on the development of reading fluency over the next 2 years after reading instruction had begun. Equally important were indications that there was no evidence of reciprocal influence of reading fluency on the growth of RAN skill. This would suggest that RAN is a function which taps the integrity of the left-hemisphere object-recognition and naming circuits which form critical components of the child's developing visual word-recognition system.

#### **4.2. The influence of instruction on rapid processing ability**

The literature, however, also indicates that rapid processing dysfunctions are responsive to training. Temple et al. [120] reported disruption of the neural response to rapid acoustic stimuli in dyslexia, with normal readers showing left prefrontal activity in response to rapidly changing, relative to slowly changing, non-linguistic acoustic stimuli. Dyslexic readers, in contrast, showed no differential left frontal response. Temple et al. also reported that dyslexic readers who participated in a remediation program showed increased activity in left prefrontal cortex after training.

Temple et al.'s results would suggest that the left prefrontal regions are normally sensitive to rapid relative to slow acoustic stimulation, but are insensitive in the case of dyslexic readers. Equally important are the indications that the left prefrontal cortex would appear to be plastic enough in adulthood to develop such differential sensitivity after intensive training.

Gaab et al. [121] reported that children with dyslexia had a fundamental deficit in processing rapid acoustic stimuli, but that this was responsive to training. While typical-reading children showed activation for rapid compared to slow transitions in left prefrontal cortex, children with developmental dyslexia did not show differential response in these regions to rapid and slow transitions in acoustic stimuli. After 8 weeks of remediation which provided training in rapid auditory processing, phonological processing and language skills, Gaab et al. reported that the children with developmental dyslexia showed significant improvements in both language and reading skills. They also showed activation for rapid relative to slow transitions in the left prefrontal cortex after training. Gaab et al. thus concluded that neural correlates of rapid auditory processing were disrupted in children with developmental dyslexia, but could be ameliorated with training.

These findings suggested that many children with reading difficulties have difficulties with rapid visual processing, difficulties with rapid auditory processing, as well as impairments of perceptual processing of rapidly changing acoustic stimuli. These findings also suggest that reading disabilities are often accompanied by impaired perceptual skills as well as specific perceptual deficits and perceptual difficulties which have neurological correlates. As with other areas of functioning, the relationship between behaviour and underlying neural connectivity would appear to be a two -way association, in which improved perceptual processing leads to improved neural connectivity, and vice versa.

#### **4.3. The magnocellular theory of dyslexia**

Talcott et al. [116] reported that both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children's literacy skills and their orthographic and phonological skills. Cohen-Mimran and Sapir [117] reported auditory temporal processing deficits in children with reading disabilities, and that children with reading difficulties had difficulty in discriminating between pure tones with short, but not long, interstimulus intervals, whereas controls performed well with both short and long interstimulus intervals.

Rapid auditory processing deficits have also been found to be consistent predictors of later reading achievement [118]. Lervåg and Hulme [119] reported that rapid automatised naming (RAN) measured with non-alphabetic stimuli before reading instruction had begun was a predictor of later growth in reading fluency, and continued to exert an influence on the development of reading fluency over the next 2 years after reading instruction had begun. Equally important were indications that there was no evidence of reciprocal influence of reading fluency on the growth of RAN skill. This would suggest that RAN is a function which taps the integrity of the left-hemisphere object-recognition and naming circuits which form

The literature, however, also indicates that rapid processing dysfunctions are responsive to training. Temple et al. [120] reported disruption of the neural response to rapid acoustic stimuli in dyslexia, with normal readers showing left prefrontal activity in response to rapidly changing, relative to slowly changing, non-linguistic acoustic stimuli. Dyslexic readers, in contrast, showed no differential left frontal response. Temple et al. also reported that dyslexic readers who participated in a remediation program showed increased activity in left prefrontal

Temple et al.'s results would suggest that the left prefrontal regions are normally sensitive to rapid relative to slow acoustic stimulation, but are insensitive in the case of dyslexic readers. Equally important are the indications that the left prefrontal cortex would appear to be plastic

Gaab et al. [121] reported that children with dyslexia had a fundamental deficit in processing rapid acoustic stimuli, but that this was responsive to training. While typical-reading children showed activation for rapid compared to slow transitions in left prefrontal cortex, children with developmental dyslexia did not show differential response in these regions to rapid and slow transitions in acoustic stimuli. After 8 weeks of remediation which provided training in rapid auditory processing, phonological processing and language skills, Gaab et al. reported that the children with developmental dyslexia showed significant improvements in both language and reading skills. They also showed activation for rapid relative to slow transitions in the left prefrontal cortex after training. Gaab et al. thus concluded that neural correlates of rapid auditory processing were disrupted in children with developmental dyslexia, but could

These findings suggested that many children with reading difficulties have difficulties with rapid visual processing, difficulties with rapid auditory processing, as well as impairments of

enough in adulthood to develop such differential sensitivity after intensive training.

critical components of the child's developing visual word-recognition system.

**4.2. The influence of instruction on rapid processing ability**

278 E-Learning - Instructional Design, Organizational Strategy and Management

cortex after training.

be ameliorated with training.

Overall, the research reviewed in the previous section would suggest that many children with dyslexia or poor reading ability have difficulties in processing rapidly changing signals, both auditorally as well as visually [122]. Visual processing difficulties, as well as auditory proc‐ essing difficulties, have neurological correlates, suggesting the possibility of a general underlying attentional or processing difficulty affecting the development of reading ability.

The magnocellular theory of dyslexia [123, 124] suggests that underlying difficulties in auditory and visual processing can be traced to difficulties in the magnocellular component of the visual system. As Stein and Walsh comment:

'Developmental dyslexics often complain that small letters appear to blur and move around when they are trying to read. Anatomical, electrophysiological, psychophysical and brainimaging studies have all contributed to elucidating the functional organization of these and other visual confusions. They emerge not from damage to a single visual relay but from abnormalities of the magnocellular component of the visual system, which is specialized for processing fast temporal information. The m-stream culminates in the posterior parietal cortex, which plays an important role in guiding visual attention. The evidence is consistent with an increasingly sophisticated account of dyslexia that does not single out either phonological, or visual or motor deficits. Rather, temporal processing in all three systems seems to be impaired. Dyslexics may be unable to process fast incoming sensory information adequately in any domain.' [125]

Stein and Walsh's conclusions have been supported by a number of studies. Salmelin et al. [126] used magnetoencephalography to identify impaired word processing in the occipitotemporal areas of dyslexics, while Livingstone et al. [127] reported that dyslexic subjects exhibited diminished visually evoked potentials to rapid, low contrast stimuli, but normal responses to slow or high contrast stimuli. Livingstone et al. suggested that the abnormalities in the dyslexic subjects' responses to evoked potentials were associated with a defect in the magnocellular pathway at the level of visual area 1 or earlier.

Livingstone et al. also compared the lateral geniculate nuclei from five dyslexic brains to five control brains, reporting abnormalities in the magnocellular, but not the parvocellular, layers in the dyslexic brains studied. As previous studies using auditory and somatosensory tests had shown that dyslexics perform poorly on tasks requiring rapid discriminations, Livingstone et al. hypothesised that many cortical systems can be divided into a fast and a slow subdivision; and further that that dyslexia is associated with difficulties in rapid processing within these fast subdivisions.

Similarly, Vidyasagar and Pammer [128] reported that impaired visual search in dyslexia relates to the role of the magnocellular pathway in attention, leading Vidyasagar [129] to suggest that attentional gating in primary visual cortex provides a physiological basis for dyslexia. Sireteanu et al. [130] also investigated the performance of children with develop‐ mental dyslexia on a number of visual tasks requiring selective visual attention and found that dyslexic children did not show the overestimation of the left visual field (pseudoneglect) characteristic of normal adult vision. Dyslexic children also showed shorter reaction times and a dramatically increased number of errors on these tasks, suggesting that children with developmental dyslexia have selective deficits in visual attention.

Misra et al. [131], for example, have identified a number of neurological correlates of rapid processing deficits, reporting that the majority of children and adults with reading disabilities also exhibit pronounced difficulties on naming-speed measures such as tests of rapid auto‐ matised naming, which required speeded naming of serially presented stimuli. In their study, functional magnetic resonance imaging was used to evaluate the neural substrates that were associated with performance on rapid naming tasks. Activation was found in neural areas associated with eye movement control and attention as well as in a network of cortical structures implicated in reading tasks, including the inferior frontal cortex, temporo-parietal areas and the ventral visual stream. Whereas the inferior frontal areas of the network were similarly activated for both letters and objects, activation in the posterior areas varied by task. These results suggested that rapid naming tasks recruited a network of neural structures which were also involved in more complex reading tasks, and suggested that rapid naming of letters pinpointed key components of this reading network.

#### **4.4. Prevalence of magnocellular deficits: Evidence from multiple case studies**

Vidyasagar and Pammer [132] have proposed that dyslexia is a deficit in visuo-spatial attention, not in phonological processing. However, the evidence from multiple case studies of disabled readers suggests that dyslexics may suffer from visual and auditory impairments but only a few suffer from a specific magnocellular deficit.

Amitay et al. [133], for example, reported that only six out of the thirty reading disabled subjects in their study had impaired magnocellular function, and that the performance of the other twenty four reading disabled subjects on magnocellular tasks did not differ from that of controls. Amitay et al. also reported that many of the reading disabled children showed impaired performance in both visual and auditory non‐magnocellular tasks which required fine frequency discriminations. Overall, Amitay et al. concluded that some reading disabled subjects have generally impaired perceptual skills, while many reading disabled subjects have more specific perceptual deficits. The 'magnocellular' level of description, however, did not capture the nature of the perceptual difficulties in any of the reading disabled individuals in the sample, as the six subjects with impaired magnocellular function were also consistently impaired on a broad range of other perceptual tasks.

Similarly, Ramus et al. [134] analysed sixteen dyslexic subjects and reported that all sixteen dyslexics suffered from a phonological deficit. Ten of the subjects could be characterised as suffering from an auditory deficit, four from a motor deficit and two from a visual magnocel‐ lular deficit. The results thus indicated that a phonological deficit can appear in the absence of any other sensory or motor disorder. A phonological deficit is also sufficient to cause a literacy impairment, as demonstrated by five of the dyslexics. Auditory disorders, when present, aggravated a phonological deficit, contributing to the literacy impairment.

Similarly, Vidyasagar and Pammer [128] reported that impaired visual search in dyslexia relates to the role of the magnocellular pathway in attention, leading Vidyasagar [129] to suggest that attentional gating in primary visual cortex provides a physiological basis for dyslexia. Sireteanu et al. [130] also investigated the performance of children with develop‐ mental dyslexia on a number of visual tasks requiring selective visual attention and found that dyslexic children did not show the overestimation of the left visual field (pseudoneglect) characteristic of normal adult vision. Dyslexic children also showed shorter reaction times and a dramatically increased number of errors on these tasks, suggesting that children with

Misra et al. [131], for example, have identified a number of neurological correlates of rapid processing deficits, reporting that the majority of children and adults with reading disabilities also exhibit pronounced difficulties on naming-speed measures such as tests of rapid auto‐ matised naming, which required speeded naming of serially presented stimuli. In their study, functional magnetic resonance imaging was used to evaluate the neural substrates that were associated with performance on rapid naming tasks. Activation was found in neural areas associated with eye movement control and attention as well as in a network of cortical structures implicated in reading tasks, including the inferior frontal cortex, temporo-parietal areas and the ventral visual stream. Whereas the inferior frontal areas of the network were similarly activated for both letters and objects, activation in the posterior areas varied by task. These results suggested that rapid naming tasks recruited a network of neural structures which were also involved in more complex reading tasks, and suggested that rapid naming of letters

developmental dyslexia have selective deficits in visual attention.

280 E-Learning - Instructional Design, Organizational Strategy and Management

pinpointed key components of this reading network.

but only a few suffer from a specific magnocellular deficit.

impaired on a broad range of other perceptual tasks.

**4.4. Prevalence of magnocellular deficits: Evidence from multiple case studies**

Vidyasagar and Pammer [132] have proposed that dyslexia is a deficit in visuo-spatial attention, not in phonological processing. However, the evidence from multiple case studies of disabled readers suggests that dyslexics may suffer from visual and auditory impairments

Amitay et al. [133], for example, reported that only six out of the thirty reading disabled subjects in their study had impaired magnocellular function, and that the performance of the other twenty four reading disabled subjects on magnocellular tasks did not differ from that of controls. Amitay et al. also reported that many of the reading disabled children showed impaired performance in both visual and auditory non‐magnocellular tasks which required fine frequency discriminations. Overall, Amitay et al. concluded that some reading disabled subjects have generally impaired perceptual skills, while many reading disabled subjects have more specific perceptual deficits. The 'magnocellular' level of description, however, did not capture the nature of the perceptual difficulties in any of the reading disabled individuals in the sample, as the six subjects with impaired magnocellular function were also consistently

Similarly, Ramus et al. [134] analysed sixteen dyslexic subjects and reported that all sixteen dyslexics suffered from a phonological deficit. Ten of the subjects could be characterised as suffering from an auditory deficit, four from a motor deficit and two from a visual magnocel‐ These data thus indicated that auditory deficits could not be characterised simply as rapid auditory processing problems, as would be predicted by the magnocellular theory. Nor were they restricted to speech. Contrary to the cerebellar theory, Ramus et al. also found little support for the notion that motor impairments had a cerebellar origin or reflected an automa‐ ticity deficit. Overall, Ramus et al. concluded that the phonological theory of dyslexia could account for all sixteen of the subjects in their sample. There were also additional sensory and motor disorders in certain individuals.

Ziegler et al. [135] reported that children with dyslexia had significant deficits for letter and digit strings, but not for symbol strings. Visual-attentional theories of dyslexia could not explain these findings, as visual attentional theories postulated identical deficits for letters, digits and symbols in dyslexics. Ziegler et al. also reported that dyslexics showed normal Wshaped serial position functions for letter and digit strings. This finding suggested that their deficit could not be attributed to an abnormally small attentional window. In addition, the data indicated that the size of the deficit was identical for letters and digits, suggesting that poor letter perception in dyslexic children was not just a consequence of lack of reading.

What could account for Ziegler et al.'s data was that the process of mapping symbols onto phonological codes was impaired, as this was the case for both letters and digits. In contrast, symbols that did not map onto phonological codes were not impaired. This dissociation suggested that impaired symbol-sound mapping rather than impaired visual-attentional processing was the key to understanding dyslexia.

#### **4.5. Both visual and visual attentional factors need to be taken into account in teaching reading**

Despite convergent evidence that dyslexia is a language disability which has its foundations in difficulties in phonological and phonemic processing, both Schulte-Körne and Bruder's [136] review and Stein's more recent [137] review of current literature suggest that rapid processing, attentional and magnocellular factors are important influences on reading ability which should not be overlooked. Research from both Australia [138] and from Italy [139] also indicate that it is important to take account of visual attentional factors in remediating language-based learning difficulties.

In addition, visual features stemming from layout of reading material have been found to influence reading as well as comprehension outcomes [140]. Spinelli et al. [141] have suggested that dyslexic readers are affected by crowding of multiple characters and large numbers of words onto printed pages. Visual features of text such as print size [142], visual span [143], spacing of letters [144], spacing between letters [145, 146], as well as font size and spacing between words relative to print size and visual acuity limits [147] are also important to consider when publishing materials for poor readers.

The above research has implications for the development of reading materials for dyslexic children. As I had found in working with Q, research post 2000 indicated that dyslexic children would be likely to respond best to reading material which took account of factors such as length of words [148, 149], amount of text in paragraphs [150] and amount of text on pages [151].

How I have taken account of phonological and phonemic factors, as well as crowding, visual and visual-attentional factors, in writing the 'Tales of Jud the Rat' series as well as in developing the procedures used in the implementation of the materials is covered in the rest of this chapter.
