Evidence of graphomotor dysfunction in children with dyslexia: A combined behavioural and fMRI experiment

Children with dyslexia (DYS) have a deficit in spelling (i.e., central processes of writing), and past experiments have suggested that they also frequently experience difficulties in handwriting (i.e., motor peripheral processes of writing) compared with typically developing children (TD). However, the presence of handwriting difficulties in dyslexia is controversial. This experiment aimed to better understand the writing difficulties in DYS children, investigating both the central and peripheral processes of writing and combining cognitive and neuroimaging data.

Participants were 14 DYS and 14 TD (Mage = 9.5) children. They were assessed on behavioural measures (i.e., spelling, handwriting and manual dexterity). Structural and functional magnetic resonance imaging (MRI) data were collected. The fMRI task was a word-dictation task performed using pencil and paper and a head coil mirror providing visual feedback.

Behavioural results revealed a clear spelling deficit and poorer handwriting in DYS than in TD. DYS and TD performed equally in handwriting speed and gross manual dexterity. fMRI data were analysed with an ROI approach using nine central ROIs and 10 peripheral ROIs, which constitute the writing network identified in past literature. fMRI results revealed less brain activation in both central and peripheral ROIs in DYS. The main peripheral differences were located in right lobule VI of the cerebellum. Structural data strengthened the presence of bilateral cerebellar abnormalities in dyslexia.

The present findings constitute a first piece of evidence that children with dyslexia's writing difficulties are not limited to the central processes of writing (i.e., spelling) and that they extend to the peripheral processes of writing (i.e., handwriting). This experiment is the first study to use an fMRI handwriting task to investigate DYS's writing abilities. These results encourage researchers to continue investigating DYS's spelling and handwriting difficulties with a neuroimaging approach. Future experiments are needed to determine whether the functional and structural anomalies observed are consequences of deviant literacy development or whether they could have a causal role in dyslexia.