Slow Saccades in Spinocerebellar Degeneration

David S. Zee, Lance M. Optican, Jay D. Cook, David A. Robinson, W. King Engel

Research output: Contribution to journalArticlepeer-review

216 Scopus citations


Two patients with spinocerebellar degeneration made abnormally slow horizontal refixations. One patient produced quick phases of nystagmus with identical maximum velocities, suggesting her refixations were abnormal saccades and not voluntary pursuit movements. In response to double target jumps, neither patient showed an obligatory refractory period after each saccade; they responded to every target movement after one reaction time. Their slow refixations were not preprogrammed since they could be modified in flight. To reconcile these observations with normal saccadic behavior, we hypothesized a neural network that made saccades by driving the eyes to an orbital position rather than preprogramming a distance for movement. Computer simulation of this model produced both realistically appearing normal saccades and, when appropriately “lesioned” to simulate a loss of saccadic “burst” neurons in the pontine reticular formation, slow saccades that could be modified in flight.

Original languageEnglish (US)
Pages (from-to)243-251
Number of pages9
JournalArchives of neurology
Issue number4
StatePublished - Apr 1976
Externally publishedYes

ASJC Scopus subject areas

  • Arts and Humanities (miscellaneous)
  • Clinical Neurology


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