Journal Of Parkinson's Disease

Bradykinesia is among the early symptoms of Parkinson’s disease (PD) and seems to be related to the patients’ difficulties to perform learned motor skills automatically. In fact, loss of automatic control has been claimed to be one of the symptoms of PD. Evidence from experimental and clinical studies has confirmed a progressive difficulty to perform learned movements automatically. In addition to deficits in movement neural coding, there would be a failure to shift execution of movements to subcortical levels. Performance of motor skills along progression of PD has been associated with increments of activity in the cerebellum, premotor area, parietal cortex, precuneus and prefrontal cortex, since these figures differ from those seen in healthy subjects; those activations are interpreted as a strategy to compensate for the basal ganglia dysfunction. Despite these neural compensatory mechanisms, the lack of automatic control of movement seem to result in impairments in gait, balance, facial expression, speech modulation, swallowing and routine tasks. In other words, automatic control seems fundamental for efficient performance in these activities.

Deficits exhibited by PD patients during performance of dual-tasks have also been associated with lack of automatic control. That is, the patients tend to engage attentional control in order to compensate for the impaired automatic control of motor performance. Consequently, the remaining attentional resources are not enough to support performance of the secondary task. In other words, deficit of performance in dual-task condition may result from decline in automaticity. 

Functionality for daily living activities dependent on the ability to perform learned movements under dual-task conditions. This would explain why PD patients exhibit difficulties for daily living activities, that is, their disturbance would be related to loss in automaticity.