The Neurobiological Development of Reading Fluency DOI: http://dx.doi.org/10.5772/intechopen.82806

### Table 3.

the other. Each word contained a letter, or group of letters, printed in pink. The child was instructed to press the button "Yes", if the pink letter(s) in the top word could stand for the same sound as the pink letter(s) in the bottom word, and to press a different button "No", if the pink letters represent different sounds.

Neurodevelopment and Neurodevelopmental Disorder

students who achieved fluent processing and those who did not [78].

would show changes in activation patterns. Through comparisons of pre-

hemisphere activation around the IFG and VWFA [78].

ical analysis task by this subject.

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noting the location, relative size, and maximum recorded t-score.

intervention processing and post-intervention processing, there are clearly subjects who demonstrate much more focused activation bilaterally in the temporal regions around the STG and Postcentral Gyrus with very little activation in the visual word form area (VWFA) in the LH occipital lobe, and others who show an increase in left

Using a clustering threshold of five voxels, a sample of the activation locations were found post-intervention in the condition of Word Pairs over Letter Match in a fluent subject. Table 3 contains a partial list of left hemisphere only activation sites,

These data confirm some anticipated activation areas with sizeable groups of voxels contributing and some remarkable lack of activation within the ROIs studied. The largest activated cluster in the IFG ROI is the Inferior Frontal Gyrus (1.52), but activation in the STG (3.10), and Brodmann areas 41 (3.17) and 42 (3.94) is much stronger. This could indicate that most of the processing in this region involved sound/symbol associations with support in the primary and auditory association cortex. The weak activation in the IFG, which supports the encoding of phonological features, could mean that less effort was required to accomplish the phonolog-

The largest activated cluster in the STG ROI is the STG (2.56), but again, other areas show stronger levels of stimulation. The Postcentral Gyrus activation (3.87) is odd in that this area is the primary somatosensory cortex receiving all sensory input, especially touch. However, except for the pressing of the response button, there was no variation in the motor demands of the scanner task that would explain activation in this area. The activation found in Brodmann areas 13 (3.08) and 40

Among other statistical procedures, the results of 1440 minutes of intervention measured in milliseconds and representing a change in speed of processing was used as a measure of achieved fluency in the Intervention group only. This sub-grouping was necessary because three individuals in the Intervention group did not achieve fluent processing with the FastWord program. This evidence of processing change was analyzed by means of a two-way mixed design ANOVA having two levels of reading fluency scores (pre- and post-intervention) as a within-subjects factor and two levels of fluency: those students (N = 6) who reached levels of emerging fluency, 100 ms or less, and those (N = 3) who did not, as a between-subjects factor. The between-subjects main effect of the fluency rate achieved during intervention was significant, F(1,8) = 5.38, p = .05, indicating significant differences between the

The fMRI results were remarkable for their corroboration of brain activations found during tasks requiring phoneme analysis. This analysis focused on three Regions of Interest (ROIs) within the core sub-systems supporting the processing of written language in normal readers: the left hemisphere (LH) superior temporal gyrus (STG) in the inferior parietal lobule within the temporoparietal system associated with word meaning; the posterior aspect of the inferior frontal gyrus (IFG) within the anterior system associated with sound/symbol associations; and the LH inferior occipito-temporal/fusiform area (VWFA) within the ventral system associated with quick recall of high frequency words first documented by Shaywitz et al. [73]. It was hypothesized that achieving fluency in reading will involve automaticity within each of these ROIs and that the brain activation maps of phonological processing of Word Pairs greater than perceptual control of Letter Match condition

Post-intervention activation locations in a fluent subject.

(3.16) makes sense in that area 40 is part of Wernicke's Gyrus where sound/symbol associations are refined and area 13 is a bridge between lateral and medial layers. The Postcentral activation could be evidence of compensatory systems being used for phonological analysis in immature processing systems.

The largest activation in the VWFA ROI is found in the smallest clusters detected. The Brodmann areas 21 (2.05) and 35 (2.01) appear to support automatic processing through their connection to Middle Temporal Gyrus, believed to access word meaning, and the perirhinal cortex, critical to memory. The left aspect of the Fusiform Gyrus shows the strongest activation (3.06) as would be expected if automatic retrieval of letter patterns was triggered [78]. So taken together, the activation locations identified in the subjects of this study, generally follow activation patterns found in the literature. Shaywitz et al. found that activation in the left occipito-temporal cortex increases with reading skill [79].

Even more unexpected, was the finding that only 1440 minutes of intervention resulted in increases in the reading speed of connected text for many subjects. Since the training mostly involved single word reading and some phrases, it was not anticipated that the intervention would make any difference in the reading of longer passages of connected text. However, this was found to be false. Six of the nine students in the Intervention Group who achieved levels of automatic


pre-intervention scan showed mostly diffuse activation in the right hemisphere occipital-parietal areas. Based on all phonetic reading errors in the pre-intervention fluency measure, this student was labeled a "P-type" and assigned the LH intervention program. MC was a very willing subject and engaged with the program easily. After progressing through the LH program (34 lessons) nearly six times during the 1440 minutes of training, the fastest processing was 80 ms with 100% accuracy. This student also achieved fluent processing rather quickly on the thirteenth day of treatment. MC gained 26 wpm on the final fluency measure. Analyzing this subject's scanner data, there was an almost perfect performance when processing the letter matches: 98% accuracy during Scan 1 and 89% accuracy during Scan 2. MC's analysis of phonemic elements improved from Scan 1–2. During Scan 1, 54% of the word pairs were correctly identified and 70% were right in Scan 2. Overall this subject demonstrated a 5% improvement in fast decoding skills. The post-intervention scan shows much more focused activation bilaterally in the temporal regions around

the superior temporal gyrus and postcentral gyrus, and there is very little

Subject 2, coded PE, was one of the students who achieved processing speeds that approached fluency using the left hemisphere program. The pre-intervention scan showed a lot of bilateral frontal activation and more RH activation than LH activation in the occipital areas. Five out of six reading errors were phonics-based, so this student was labeled "P-type" and assigned the LH program. PE completed the LH program six times during 1440 minutes of treatment, but there were only 24 lessons included because some of the orthographic patterns were not taught at this reading level. This student was one of the younger participants in the study and only reached levels of fluent processing for words, not for phrases. PE's fastest processing score was 125 ms with 83% accuracy and during post-intervention fluency measures, reading speed was increased by 11 wpm. Analyzing the scanner data, there is evidence of significant learning, perhaps due to the young age and the nature of reading instruction in the lower grades. PE showed a lot of confusion when analyzing the letter strings: only 49% were judged correctly in Scan 1 and 57% in Scan 2. Growth in decoding skills is evident in the correct identification of the word pairs: 45% during Scan 1 and 62% during Scan 2. Overall, this subject demonstrated a 13% improvement in fast visual processing. The post-intervention scan indicates an increase in left hemisphere activation around the inferior frontal gyrus

So if the focus is on automatic word retrieval, the Visual Word Form Area, has to be a region of exceptional interest. There remains much to understand regarding the activation of the Visual Word Form Area in the left fusiform gyrus and its relationship to the development of fluent reading. According to Cohen et al., a standard model of word reading proposes that visual information is initially processed by occipito-temporal areas contra-lateral to the stimulated hemi-field. Then it is transferred to the visual word form system (VWFA), a left temporal region devoted to the processing of letter strings. Using fMRI, they identified a highly significant activation in the left fusiform gyrus (Talairach coordinates: x = 42, y = 57, z = 6) that was strictly unilateral and remarkably stable across subjects [80]. Since their research also included comparisons of activation from the right and left visual

hemi-fields, they concluded that the VWFA lies at the convergence of

retinotopically organized visual pathways and contain visual neurons with receptive fields in both hemi-fields. They hypothesize that the VWFA may be homologous to inferotemporal areas in the monkey where cells with wide receptive fields, selectivity to high-level visual features, and size and position invariance have been found. If this is the case, it is possible that the human VWFA holds a distributed

activation in the VWFA in the LH occipital lobe [78].

The Neurobiological Development of Reading Fluency DOI: http://dx.doi.org/10.5772/intechopen.82806

and VWFA [78].

105

### Table 4.

Summary of behavioral results.

processing (<100 ms) in either the left- or right visual hemi-field, also increased their reading rate by an average of 20 wpm [78]. See Table 4.

There is considerable evidence that different students responded to the intervention differently. Those students who only displayed phonics-based errors in reading connected text and worked for the entire intervention time in the LH Program seemed to make the most substantial increases in both processing and reading speed. Only one student who demonstrated meaning-based errors and used the RH Program exclusively showed faster processing during intervention. The students who displayed both types of errors and split their time between programs made the least amount of progress; two reached fluency in the LH Program, but not in the RH Program. It is suggested that continued work with the intervention program could achieve the desired level of automaticity and that strengthening processing in the right hemisphere is inherently more difficult than strengthening the left hemisphere [78].

Wolf cautions that another source of reading disability could be an impediment in the circuit connections among the brain structures, stressing the importance of understanding the connectivity among the various regions instrumental to reading performance. She proposed at least three forms of disconnections which are consistently studied: between the frontal and posterior language regions based on underactivity in the connecting insula; and between the occipital-temporal region or the left angular gyrus region; and frontal areas in the left hemisphere. She suggests that children with dyslexia use an altogether different reading circuitry. Instead of a progressive disentanglement of the right hemisphere's larger visual recognition system in reading words and an increasing engagement of left hemisphere's frontal, temporal, and occipital-temporal regions, they used more frontal regions, showed less activity in the left-hemisphere angular gyrus, and created potentially compensatory "auxillary" right-hemisphere regions which performed functions usually handled by more efficient left-hemisphere areas [14]. The fMRI results from this study underscore Wolf's proposal. It may be that much of the diffuse frontal activation that was observed in many pre-intervention scans and some postintervention scans of nonfluent subjects is evidence of these compensatory "auxillary" strategies. It may be that in older readers who have over time consolidated less efficient pathways for reading, more exposure is required for specific hemispheric stimulation (intervention) to supplant frontal and right hemisphere functions with effective left hemisphere processing.
