Introduction

1. 1a 1b Anchor Ship Truck 2a 2b 3a 3b Cup Axe Slide 4a 4b Functional and structural brain abnormalities in developmental dyslexia: The role of the cerebellum and occipitotemporal lobe Clare Shakeshaft, Cathy Price & HweeLing Lee Exp 3: Music Reading Task Introduction Fig. 2. Stimuli used for Exp. 2. (1a) Semantic decisions on Words (1b) Perceptual decisions on triads of meaningless symbols; (2a) Semantic decisions on Pictures; (2b) Perceptual decisions on triads of meaningless non objects; (3a) Reading aloud Words; (3b) Saying “one, two three” to triads of meaningless symbols; (4a) Naming aloud Pictures; (4b) Saying “one, two three” to triads of meaningless non objects Background Method • Are differences in brain activation are observed in the same regions that show differences in brain structure? • Impairments in development dyslexia are not confined to reading and literacy skills. Additional behavioural deficits include phonological processing, motor skills and automatic balance. These difficulties are not observed consistently and vary from individual to individual. • Do some dyslexics have multiple impairments at the neurological level? Or might there be a single causal mechanism that accounts for all problems? • Subjects indicated the position of four black dots in a simple music note reading task that did not involve phonological or semantic processing. • Vocal and manual responses were made with corresponding baseline conditions. Functional Imaging Studies Fig 5. Stimuli used for music reading task in activation condition (left) and baseline condition (right). • Many areas of abnormal activation observed (including cerebellum), but not consistent across studies and usually confounded by task performance differences. • Left occipito-temporal cortex abnormalities are observed during both reading and picture naming (McCrory et al., 2005) when task performance difficulties explicitly controlled. • It is important to investigate other neural substrates that may contribute to impairments that manifest behaviourally in dyslexia, such as the cerebellum (Nicolson et al., 1999). Results • Both dyslexics and controls activated the same cerebellar region found to be structurally abnormal in Exp.1. Results Exp 1: Structural Scan 1) The same midline cerebellar region was activated during reading in dyslexics and controls as reported in Exp. 1. Fig. 6. Activation in sensori-motor integration in the same region of the cerebellum (yellow) as Exp 1. Method • Do dyslexic individuals show differences in brain structure relative to age matched controls without reading difficulties? • 34 dyslexic subjects and 17 controls scanned using a whole brain unbiased objective technique, voxel based morphology (VBM). Fig. 3. Reading activation in both groups at the same coordinates of the structural abnormality in the same midline cerebellar region Conclusion Results • Activation in this area reflects non-verbal sensori-motor integration. • Structural analyses revealed grey matter density increased with spelling ability in a region of the midline cerebellum. Summary 2) Dyslexics showed reduced activation relative to controls in the right occipito-temporal cortex during all tasks, irrespective of whether the stimuli were meaningful and meaningless. 3) Reduced activation in the dyslexic group relative to the controls in the left occipito-temporal cortex for naming and semantic tasks with meaningful stimuli only. • This study shows structural abnormalities in a region of the cerebellum that may mediate spelling and reading ability in developmental dyslexia. • Structural abnormalities in this cerebellar region are associated with sensori-motor integration. • Functional abnormalities are reported in the left occipito-temporal cortex for meaningful stimuli only, therefore this region is not specific to phonology. • Impaired phonological abilities in dyslexic behaviour may reflect a more general deficit in sensori-motor integration. Fig 1. Localisation of reduced grey matter density in a midline cerebellar region when correlated with spelling (comparisons across all subjects) Fig. 4. Reduced activation in dyslexics relative to the controls in right fusiform gyrus for all perceptual and semantic tasks with meaningful and meaningless stimuli (red). Reduced activation in the dyslexic group relative to controls in the left fusiform gyrus for naming and semantic tasks with meaningful stimuli only (yellow). Conclusion Selected References • This shows a region of the cerebellum whose structure reflects spelling ability. Exp 2: Reading, Naming & Semantic Decisions 1] McCrory, E., Mechelli, A., Frith, U., and Price, C., (2005) More than words: A common neural basis for words and naming deficits in developmental dyslexia? Brain, 261-267. 2] Nicolson, R.I., & Fawcett, A.J., Berry, E.L., Jenkins, I.H., Dean, P., & Brooks, D.J. (1999) Association of abnormal cerebellar activation with motor learning difficulties in dyslexic adults. Lancet, 353, 1662-1667. Method Conclusion • Subjects scanned during word reading, picture naming, semantic decisions on written words or pictures of objects and perceptual decisions on meaningless non-objects or symbols. • Only subjects with accuracy of 85% and over in naming condition included in analyses, resulting in 20 dyslexics and 14 controls.  • The deficit observed in the occipito-temporal region is not specific to phonology.