Friedreich ataxia is characterized by progressiveness of motor coordination that is linked to peripheral, spinal, and cerebellar neuropathology. Cerebral abnormalities are also reported in Friedreich ataxia, but their role in disease expression remains unclear.
In this cross-sectional functional magnetic resonance imaging study, 25 individuals with Friedreich ataxia and 33 healthy controls performed simple (self-paced single-finger) and complex (visually cued multifinger) tapping tasks to respectively gauge basic and attentionally demanding motor behavior. For each task, whole brain functional activations were compared between groups and correlated with disease severity and offline measures of motor dexterity.
During simple finger tapping, FA patients at the lower end oft he clinical severity scale showed more activation, while those more affected by disease showed less activation in certain regions of the cerebrum. Greater activation in this network correlated with greater offline finger tapping precision. Complex, attentionally demanding finger tapping was also associated with cerebral hyperactivation, but in this case within different regions. Greater offline motor precision was associated with less activation in the dorsal attention network.
Compensatory activity is evident in the cerebral cortex in individuals with Friedreich ataxia. Early compensation followed by later decline in premotor/ventral attention systems demonstrates capacity-limited neural reserve, while the additional engagement of higher order brain networks is indicative of compensatory task strategies. Network-level changes in cerebral brain function thus potentially serve to mitigate the impact of motor impairments in Friedreich ataxia.
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