Differences in saccade dynamics between @entity196 and XXXX @entity6447 .

@entity1 @entity196 @entity854 @entity32889 @entity76 @entity6447 @entity164
The cerebellum is implicated in maintaining the saccadic subsystem efficient for vision by minimizing movement inaccuracy and by learning from endpoint errors. This ability is often disrupted in @entity76 , as demonstrated by saccade @entity854 . The study of saccades in these @entity1 may therefore provide insights into the neural substrate underlying saccadic motor control. We investigated the different extent of saccade @entity854 in @entity196 and @entity32889 @entity6447 , genetically undefined and with prevalent @entity76 . Reflexive and voluntary saccades of different amplitude (10  -18  ) were studied in seven @entity1 with @entity196 , eight @entity1 with @entity32889 @entity6447 and 25 healthy controls. Quantitative analysis of saccade parameters and measures of saccade accuracy were performed. Detailed neurological, neurophysiological and magnetic resonance imaging assessment was obtained for each @entity1 . Genetic and laboratory screening for @entity164 and other forms of @entity32889 @entity6447 were also performed. A lower peak saccade velocity and longer duration was observed in @entity1 with @entity196 with respect to those with @entity32889 @entity6447 and controls. Unlike subjects with @entity196 , @entity1 with @entity32889 @entity6447 showed main sequence relationships to similar saccades made by normal subjects. Saccades were significantly more inaccurate, namely hypometric, in @entity32889 @entity6447 than in @entity196 and inaccuracy increased with saccade amplitude. The percentage of hypometric primary saccades and of larger secondary corrective saccades were consistently higher in @entity32889 @entity6447 than in @entity196 and controls. No other significant differences were found between groups. Two different mechanisms were adopted to redirect the fovea as fast and/or accurately as possible to peripheral targets by the two groups of cerebellar @entity1 . @entity1 with @entity196 maintained accuracy using slow saccades with longer duration. This reflects prevalent degenerative processes affecting the pontine burst generator and leading to saccade velocity failure. On the other hand, @entity1 with @entity32889 @entity6447 reached the target with a number of fast inaccurate, mostly hypometric saccades. Different degrees of cerebellar oculomotor vermis involvement may account for differences in optimizing the trade-off between velocity and accuracy in the two groups. In addition, as suggested by spinocerebellar @entity1 having slow saccades that are no longer ballistic, visual feedback might be continuously available during the movement execution to guide the eye to its target.
