Association of abnormal cerebellar activation with motor learning difficulties in dyslexic adults

In addition to their impairments in literacy-related skills, dyslexic children show characteristic difficulties in phonological skill, motor skill, and balance. There is behavioural and biochemical evidence that these difficulties may be attributable to mild cerebellar dysfunction. We wanted to find out whether there was abnormal brain activation when dyslexic adults undertook tasks known normally to involve cerebellar activation.

Brain activation was monitored by positron emission tomography in matched groups of six dyslexic adults and six control adults as they carried out either a prelearned sequence or learned a novel sequence of finger movements.

Brain activation was significantly lower (p<0.01) for the dyslexic adults than for the controls in the right cerebellar cortex and the left cingulate gyrus when executing the prelearned sequence, and in the right cerebellar cortex when learning the new sequence.

The results provided direct evidence that, for this group of dyslexic adults, the behavioural signs of cerebellar abnormality reflect underlying abnormalities in cerebellar activation.