Directional reversal of saccadic dysmetria and gain adaptivity in a patient with a superiorl6cerebellar artery infarction

Abstract

Saccadic horizontal eye movements were explored in a 46-year old patient with a unilateral infarction in the cortico-cerebellar territory of the right superior cerebellar artery, involving vermal folia VI and VII. Eye movements were recorded with the search coil method ten days, and eight and 20 months after the infarction. Gain adaptivity of saccades was tested in the chronic stage only with the double target step paradigm which experimentally induced hypermetria of saccades.The patient had persistent and direction-specific saccadic dysmetria. Acutely, i.e., ten days after the stroke, saccades to the lesion side were strongly hypometric and those to the normal side tended to be hypermetric. In the chronic stage, i.e., months later, the directionality of saccadic dysmetria was reversed: ipsiversive saccades were now hypermetric whereas contraversive saccades tended to be hypometric.There is strong evidence that gain adaptivity of saccades in the chronic stage was diminished (it has not been tested in the ...