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

Background In addition to their impairments in literacy-related skills, dys lexic children show characteristic difficulties in phonological skill, moto r skill, and balance. There is behavioural and biochemical evidence that th ese difficulties may be attributable to mild cerebellar dysfunction. We wan ted to find out whether there was abnormal brain activation when dyslexic a dults undertook tasks known normally to involve cerebellar activation. Methods Brain activation was monitored by positron emission tomography in m atched groups of six dyslexic adults and six control adults as they carried out either a prelearned sequence or learned a navel sequence of finger mov ements. Findings Brain activation was significantly lower (p<0.01) far the dyslexic adults than for the controls in the right cerebellar cortex and the left c ingulate gyrus when executing the prelearned sequence,and in the right cere bellar cortex when learning the new sequence. Interpretation The results provided direct evidence that, for this group of dyslexic adults, the behavioural signs of cerebellar abnormality reflect u nderlying abnormalities in cerebellar activation.