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Hemispheric specialization refers to the fact that cerebral hemispheres are not equivalent and that cognitive processes are lateralized in the brain. Although the potential links between handedness and the left hemisphere specialization for language have been widely studied, little attention has been paid to other motor preferences, such as eye dominance, that also are lateralized in the brain. For example, saccadic accuracy is higher in the hemifield contralateral to the dominant eye compared to the ipsilateral hemifield. Saccade accuracy is, however, also known to be sensitive to other functional asymmetries, such as the lateralization of visuo-spatial attention in the right hemisphere of the brain. Using a global effect paradigm in three different saccade latency ranges, we here propose to use saccade accuracy as an indicator of visual functional asymmetries. We show that for the shortest latencies, saccade accuracy is higher in the left than in the right visual hemifield, which could be due to the lateralization of visuo-spatial attention in the right hemisphere. For the longest latencies, however, saccade accuracy is higher toward the right than the left hemifield, probably due to the lateralization of local and global processing in the left and right hemispheres, respectively. These results could have a major impact on studies designed to measure the degree of lateralization of individuals. We here discuss both the theoretical and clinical contributions of these results. [ABSTRACT FROM AUTHOR]

To determine the adaptive capability of saccadic eye movements, and its association with enduring saccadic dysmetria in cerebellar and lateral medullary infarction (LMI), we investigated saccadic accuracy and adaptation in 15 patients with cerebellar or lateral medullary infarction, compared with those of 7 patients with diffuse cerebellar atrophy and 11 normal subjects. Saccade adaptation was elicited by a 37.5% backward target step during the primary saccade in both horizontal directions. Horizontal preadaptive saccadic gains were decreased in patients with cerebellar infarction, and contralesionally in patients with LMI. In contrast, adaptive saccadic gain change was reduced in patients with diffuse cerebellar atrophy and cerebellar infarction. Saccadic hypometria and reduced saccadic adaptability were dissociated in the majority of the patients with cerebellar infarctions; seven of the eight patients with cerebellar infarction showed saccadic hypometria and only three of them showed reduced saccadic adaptation, uni- or bilaterally in two with bilateral infarctions and ipsilesionally in one with unilateral infarction. The most commonly affected structure on MRI was the cerebellar hemisphere in the patients either with saccadic hypometria or with reduced saccadic adaptation. All patients with unilateral LMI exhibited normal saccadic gain adaptation in both directions, including those patients with enduring saccadic ipsipulsion. Our results suggest that the cerebellar hemispheres as well as the dorsal vermis and fastigial nucleus may be involved in the control of saccadic accuracy and adaptation. Reduced saccadic adaptation and persisting dysmetria are not tightly linked to each other in the cerebellar or lateral medullary lesions. [ABSTRACT FROM AUTHOR]