Deficits in ocular and manual tracking due to episodic ataxia type 2.
Four patients with a novel mutation leading to episodic ataxia type 2 were studied in a task that required them to track target motion either with the eyes or with the index finger of the right hand. The target initially moved in a straight line and then changed direction at an unpredictable time by an unpredictable amount. On the day of testing, 3 of the patients were evaluated as normal on a neurological exam, whereas the fourth was severely ataxic. Nevertheless, all 4 showed deficits in tracking behavior with common features. Ocular tracking tended to result in hypermetric saccades at longer than normal latencies. Smooth pursuit tracking was absent in 1 patient and had lower than normal gain in the others. Deficits in manual tracking showed similarities to the deficits in ocular tracking, with hypermetric compensations for changes in target direction. The similarities in the deficits in manual and ocular tracking suggest that they are subject to similar control by the cerebellar structures.
Engel
Kevin C
KC
Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA.
Anderson
John H
JH
Department of Otolaryngology, University of Minnesota, Minneapolis, Minnesota, USA.
Gomez
Christopher M
CM
Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA.|Department of Neurology, University of Minnesota, Minneapolis, Minnesota, USA.
Soechting
John F
JF
Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, USA.
D000328:Adult; D000368:Aged; D001259:Ataxia / Q000145:classification* / Q000503:physiopathology*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology*; D006225:Hand / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011597:Psychomotor Performance / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D012720:Severity of Illness Index; D013997:Time Factors