Monzani, B;
(2008)
Neural and behavioural differences between subgroups of subjects with dyslexia.
Doctoral thesis , UCL (University College London).
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Abstract
A literature review on neuroimaging research on developmental dyslexia (DD) highlights inconsistencies regarding the structural and functional abnormalities underling the disorder. The discrepancies in findings have been partly attributed to the heterogeneity of DD, thus instigating researchers to study whether the disorder can be categorized into different subtypes, reflecting distinct neural and behavioural phenotypes. The following fMRI study was conducted to identify subgroups of dyslexics on the basis of their brain activation for reading aloud by using an unbiased classification method (PCA/GMM). The study then aimed to establish structural and behavioural differences distinguishing the subgroups. Thirty-four subjects with dyslexia and 34 non- impaired readers were scanned using fMRI and assessed using varies psychometric tests. A one sample t-test was used to add together functional images from subjects and treat the inter-subject variability as error variance. PCA and GMM then allowed the identification of subgroups and assignment of subjects to the groups, while statistical analyses highlighted brain activation and behavioural differences between the subgroups. Three subgroups of dyslexics (Dl, D2, and D3) were identified. Results showed that Dl overactivated bilateral superior temporal gyri whereas D2 and D3 showed abnormal underactivations in 3 areas (bilateral temporo-parietal cortex, left occipito-temporal cortex, and cerebellum). D3 also tended to perform worse on most psychometric tests, and statistically worse on auditory short term memory tasks. Findings of differences in activation patterns and behavioural performance between the subgroups dyslexic may support the existence of subtypes of dyslexia, where one subgroup reflects compensated dyslexics while the another is characterized by auditory short term memory deficits.
| Type: | Thesis (Doctoral) |
|---|---|
| Title: | Neural and behavioural differences between subgroups of subjects with dyslexia |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| UCL classification: | UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1569510 |
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