Distinct patterns of brain function in children with isolated spelling impairment: new insights.

Studies investigating reading and spelling difficulties heavily focused on the neural correlates of reading impairments, whereas spelling impairments have been largely neglected so far. Hence, the aim of the present study was to investigate brain structure and function of children with isolated spelling difficulties. Therefore, 31 children, aged ten to 15 years, were investigated by means of functional MRI and DTI. This study revealed that children with isolated spelling impairment exhibit a stronger right hemispheric activation compared to children with reading and spelling difficulties and controls, when engaged in an orthographic decision task, presumably reflecting a highly efficient serial grapheme-phoneme decoding compensation strategy. In addition, children with spelling impairment activated bilateral inferior and middle frontal gyri during processing correctly spelled words and misspelled words, whereas the other two groups showed bilateral activation only in the misspelled condition, suggesting that additional right frontal engagement could be related to generally higher task demand and effort. DTI analyses revealed stronger frontal white matter integrity (fractional anisotropy) in controls (compared to spelling and reading impaired children), whereas no structural differences between controls and spelling impaired children were observed.