Memory-based smooth pursuit: neuronal mechanisms and preliminary results of clinical application

Using a memory-based smooth-pursuit task, macaque monkeys were trained to pursue (i.e., go) or not pursue (i.e., no-go), a cued direction, based on the memory of visual motion-direction and a go/no-go instruction. Task-related neuronal activity was examined in the supplementary eye fields, caudal frontal eye fields, cerebellar floccular region, dorsal vermis lobules VI-VII, and caudal fastigial nuclei. Different cerebral and cerebellar areas carried distinctly different signals during memory-based smooth pursuit. Chemical inactivation of these areas produced effects consistent with the differences in signals represented in each area. This task was applied to patients with idiopathic Parkinson's disease (PD), because impaired visual working memory has been reported during cognitive tasks in PD. None of the PD patients tested exhibited impaired working memory of motion-direction and/or go/no-go selection, but they had difficulty in preparing for and executing smooth-pursuit eye movements, suggesting a selective motor-related disturbance in Parkinson's disease.