Dyslexia therapy customization based on dorsal-ventral pathway representation
Sunita Gudwani1, Senthil Kumaran1, Rajesh Sagar2, SN Dwivedi3, and Naranamangalam R Jagannathan1

1Department of NMR and MRI Facility, All India Institute of Medical Sciences, New Delhi, India, 2Department of Psychiatry, All India Institute of Medical Sciences, New Delhi, India, 3Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, India


Reading necessitates skill mastering of phonological (sound to letter), orthographic (knowledge of letter identities, position), and semantic (words meaning) processing requiring optimal interface of ventral-dorsal routes. Dyslexia, a developmental reading disorder, is an umbrella term with heterogeneity of behavioral deficits constrains the management efficiency. Persistent deficits lead to emotional, academic, social consequences necessitating evidence-based interventions. The study was planned on neurobiological-model to customize the therapeutic management. Dorsal pathway (BOLD activation) reorganization associated with improvement in reading rate, accuracy, spelling and writing flow suggest neurobiological normalization in dyslexics observed post-remediation on comparing therapy group with non-therapy and age-matched typical readers.


Dyslexia is neuro-developmental, specific learning disorder with deficits of phonological awareness, processing speed, working memory, executive function and orthographic decoding abilities, leading to reading difficulties1-3. It is a heterogeneous condition with variability in manifestations of deficits4,5 where the cortical areas or their connections may help us to understand the phenomenon6. Rehabilitative measures are not generally based on basic neurobiological principles, despite evidence from animal models, anatomical and in-vivo human brain reorganization6,7. Thus, in this study, interventional programs are customized evidence based, clinical performance, and functional MRI (fMRI), for efficient outcome measures8.


Task based fMRI gives visible and quantifiable neurobiological difference(s) associated with specific psychological symptoms in dyslexia, where inferior frontal cortex of dorsal stream reveals cortical signature for monitoring behavioral remediation6,9. Hypothesis was made to plan the management based on these neuro-functional differences for optimal normalization and to observe the outcome by behavioral and brain measures.


Study was randomized controlled, with therapy (Rx group, n = 12, mean age: 11.38±2.41 years) and non-therapy (nonRx group, n = 12, mean age: 11.09±2.71 years) dyslexic groups compared with age-matched (n=12, 12.06±2.33 years) healthy control children. Remediation consisted of 28-30 sessions (6 months), techniques based on the neurobiological approach drilled for multiple times (Hebbian principle)10-14. Therapeutic targets, namely, (i) visual training for focusing, attentional filtering, inhibition of distracters, grapheme discrimination; (ii) auditory training for phonological awareness; (iii) kinesthetic-sensory-motor articulation training for phonological errors; (iv) working memory and executive control; (v) language enrichment at lexical, semantic and syntactic levels; (vi) generalization to reading, were prioritized/chosen based on BOLD activation as positive and negative signs. Baseline and post-therapy investigations included clinical assessment and task based fMRI (phonological, lexico-semantic and syntactic processing) acquired with 32 channel head coil in 3T MR scanner (Achieva M/s. Philips HealthCare, The Netherlands); using EPI with parameters echo train length 33, TR 2 s. Data were processed in SPM12. The visual tasks were presented using E-Prime (version 1.1, Psychology Software Tools Inc, USA) on a LCD monitor (ESys fMRI System, Invivo Corp, M/s. Philips Healthcare). Phonological (word-pseudowords judgment) and lexico-semantic (abstract-concrete nouns) tasks consisted of 222 dynamics and syntactic (simple sentences) task, 90 dynamics. Clinical data was analyzed using SPSS (version 17, SPSS Inc., IBM Business Analytics).

Results and Discussion

At baseline, in typical readers (age-matched healthy control) the fast-guess inhibition mechanism for pseudowords (nonwords) was observed in comparison to meaningful words and the lexico-semantic judgment showed top-down processing in clinical performance and BOLD activation. In dyslexics, the inhibitory fast-guess mechanism for nonwords was non-differentiable and orthographic-phonological (O<=>P) BOLD activation during meaningful judgment was modified (top-down processing). Ventral lexico-semantic pathway was involved while processing abstract nouns in dyslexic and healthy control children, whereas dorsal-route executive control was modified in dyslexics as compared to controls, in concordance with literature6,15,16. The ventral regions are attributed to integrating bottom-up processing (feed-forward) and dorsal route processing influence reading (irrespective of task) by top-down gating, but the strength is modulated by task and attention15. Post diagnosis as dyslexic, the children were randomly allocated into two groups (Rx and nonRx groups) following CONSORT 2010 and post-hoc group analysis (Bonferroni test) showed statistically non-differentiable difference at baseline, delineating appropriate randomization.

Post-therapy changes were assessed with repeated measure ANOVA for clinical performance (summarized in figure 1, table 1) and with ANOVA for BOLD activation (Figures 2, 3), which show the statistical significant difference in clinical performance and changes during phonological, lexico-semantic and syntactic processing suggestive of improvement at behavior level (reading rate 0.609 words per second, spelling errors <25%, rate of written expression 0.194 words per second) and BOLD reorganization in dorsal-ventral interface (including frontal-parietal and temporo-occipital areas; BA 6, 9, 10, 11, 44, 45, 47, 13, 21, 22, 37, 39, 17, 18, 19 and BA 31, 32) attributing to top-down executive control of dorsal route. Thus, planning remediation strategies based on brain measures along with behavioral performance optimize the improvement as normalization rather than compensatory changes 1,6,10, 11.


No acknowledgement found.


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Figure 1. Comparing clinical performance of Rx (n=12), nonRx (n=12) at follow-up and age-matched healthy control (n=12) groups.

Table 1. Comparing Controls (n = 12), therapy (Rx Follow-up n = 12), non-therapy (nonRx Follow-up n=12) groups for clinical performance; Reading rate: rate of reading paragraph in wps (words per second); Reading errors: number of phonological+morphophonemic errors (%) while reading paragraph; Spelling errors: errors while word dictation; Writing rate (in words per second) was flow of writing a paragraph on a topic of child’s own choice; performance in English was assessed on subtest of NIMHANS index for SLD

Figure 2. Comparing BOLD activation during phonological processing in Rx (n=12) and nonRx (n=12) dyslexics (using ANOVA test, p < 0.001, Z-score: 3.0; voxel threshold: 10) rendered on standard template; SFG- superior frontal gyrus, MFG- middle frontal gyrus, IFG- inferior frontal gyrus, Postcentral- postcentral gyrus, STG- superior temporal gyrus

Figure 3. Comparing BOLD activation during English syntactic processing in Rx (n=12) and nonRx (n=12) dyslexics (using ANOVA test, p < 0.001, Z-score: 3.0; voxel threshold: 10) rendered on standard template

Proc. Intl. Soc. Mag. Reson. Med. 25 (2017)