van den Bunt, M. , Groen, M. & Verhoeven, L.
Behavioural Science Institute, Radboud University, The Netherlands
Poor phoneme representations are hypothesized to be a core deficit in individuals with developmental dyslexia (DD). Recent neurocomputational models suggest that the quality of these phoneme representations are dependent on the integrity of speech sensory and speech motor feed-forward and feedback mechanisms. In a recently submitted paper, we examined these mechanisms using altered auditory feedback and showed that participants with DD are more sensitive to this perturbation compared to a typically reading group. In this study, we examined whether these differences in sensitivity are reflected in structural brain differences between speech perception and production areas. The white matter fractional anisotropy of the arcuate fasciculus was measured in 21 adults with DD and 20 typically reading individuals, using Tract-Based Spatial Statistics. A group comparison showed a significantly reduced fractional anisotropy in the left arcuate fasciculus in the DD sample. Additionally, the response to altered auditory feedback was related to the anisotropy in the same tract. These results further establish the important role for speech perception-production processes in DD. In the future we will include additional measures such as the myelination and neurite orientation dispersion in the arcuate fasciculus to further clarify the neural basis of the phonological deficit in DD.