White matter integrity of cerebellar-cortical tracts in reading impaired children: A probabilistic t ra c t o g ra p h y s t u d y. B ra i n & Language

The tracts analysed included the contralateral and ipsilateral tracts originating in the anterior lobe of the cerebellum and connecting with the temporoparietal (TP), occipitotemporal (OT) and inferior frontal (IF) cortices which are typically associated with reading. Right handed children aged 6 to 15 years were recruited and divided into 2 groups: 29 children with decoding impairment (I.e.: <26th percentile on single word decoding, comprehension and fluency impairments) and 27 typically developing children (I.e.: No impairment in current or past reading measures). The reading accuracy/ decoding abilities in these children were measured using the Woodcock-Johnson III Letter Word Identification (LWI) and the Wide Range Achievement Test. Fluency was assessed using the Sight Word Efficiency (SWE) and Phonemic Decoding Efficiency subtest (PDE). Comprehension was assessed using the Passage Comprehension measure from the Woodcock Johnson III Test, and intellectual function was evaluated using the Kaufman Brief Intelligence Test-2nd edition (KBIT-2). The structural integrity of white matter was measured using Fractional anisotropy (FA). Overall, the poor group of readers performed below the typical group of readers across decoding, reading comprehension and fluency, as expected. Group differences in IQ were also observed. The researchers found greater FA values were apparent in white matter fibre tracts connecting the cerebellum with the TP and IF region bilaterally in the poor readers compared to typical readers. An interesting note from the researchers as to increase FA in these children is that “reading requires a careful orchestration of motor, cognitive and sensory processes to produce accurate and fluent word reading.” Myelination and/or dense axonal packaging may be the cause of the increased in FA value. Interestingly, in the OT region, FA was greater for the older poorer readers, however smaller for the younger ones when comparing to typical readers. This study provides insight into the regulatory functions of the cerebellum in integrating and automating reading skills.