Basal ganglia dysfunction reduces saccade amplitude during visual scanning in Parkinson's disease

For Parkinson's disease (PD), we have reported that small saccades restrict visual scanning (Matsumoto H, Terao Y, Furubayashi T et al. Small saccades restrict visual scanning area in Parkinson's disease. Mov Disord 2011;26:1619-26), possibly resulting in the disturbances of visual attention in PD. However, it remains unknown why the saccade amplitude is reduced during visual scanning. The aim of this paper is to study whether the small saccade amplitude during visual scanning results from basal ganglia (BG) dysfunction. This study examined 18 PD patients. The saccade amplitude during viewing visual images was recorded. The saccade amplitude in oculomotor tasks, visually guided saccades (VGS) and memory-guided saccades (MGS) were also recorded. We analyzed the correlation between the saccade amplitude during visual scanning and the saccade amplitude during oculomotor tasks. The saccade amplitude during visual scanning was reduced compared to normal subjects. Similarly, the saccade amplitudes in both VGS and MGS were also reduced. However, the saccade amplitude during visual scanning always correlated with MGS amplitude, whereas it hardly related to VGS amplitude. Our results indicate that BG dysfunction might reduce the saccade amplitude during visual scanning in this disorder.

► Saccade amplitude during visual scanning was smaller in Parkinson's disease patients. ► The saccade amplitude significantly correlated with the amplitude of memory-guided saccades. ► Basal ganglia dysfunction might reduce the saccade amplitude during visual scanning.