Impairment in motor reprogramming in Friedreich ataxia reflecting possible cerebellar dysfunction

Abstract

The cerebellar and spinocerebellar dysfunction seen in Friedreich ataxia (FRDA) has known effects on motor function. Recently, it was suggested that people with FRDA may also have impairment in motor planning, either because of cortical pathology or because of cerebello-cortical projections. Fifteen adults with FRDA and 15 matched controls completed a task requiring reciprocating movements between two buttons on a tapping board. Occasionally there was one of three "oddball" stimuli requiring reprogramming of movement. These were change in (1) direction, (2) extent or (3) direction and extent. We hypothesized that people with FRDA would have prolonged movement times due to their movement disorder, and that changes in preparation time would be affected in a way similar to controls, unless there was impairment in motor planning in FRDA. Movement execution and, to a lesser degree, movement preparation were impaired in individuals with FRDA. We argue this points to disturbed cortical function. There was a significant negative correlation between age of onset and all three reprogramming conditions, suggesting an impact of FRDA on developing motor planning. Future studies will be required to establish whether this dysfunction is due to cerebellar impairment interrupting cerebro-ponto-cerebello-thalamo-cerebral loops, primary cortical pathology or a combination of the two.