Lance M. Optican, Ph.D.

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Presentations

Dual Pathway Model of the Saccadic System

Papers

• P. Lefévre, C. Quaia, L.M. Optican: Distributed model of control of saccades by superior colliculus and cerebellum. Neural Networks 11: 1175-1190, 1998

• C. Quaia, P. Lefévre, L.M. Optican: Model of the control of saccades by superior colliculus and cerebellum. J. Neurophysiol. 82: 999-1018, 1999

Presentations *

• IEEE Engineering in Medicine and Biology Society, 2001

• Presentation of dual pathway model

• Presentation: Distributed Model of Collicular and Cerebellar Function During Saccades, presented at Neurobiology of Eye Movements: From Molecules to Behavior, Oct. 2001, Cleveland, OH.

Simulations

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(BN = Burst Neurons, BUN = Buildup Neurons, FOR = Oculomotor Region of the Fastigial Nucleus)

• Oblique Saccade (MPEG) (3.2 MB)
  This movie shows activity in three cell types in the superior colliculus (fixation, buildup and burst), activity on both sides of the fastigial nucleus, and the eye movement (in a horizontal versus vertical plot). Prior to a saccade, the fixation cells are active. During a saccade, the activity starts in the buildup neurons, and spreads rapidly to the front of the superior colliculus, after which the buildup and burst neurons both burst. At the time of the burst, the activity in the fastigial nuclei begins to spread, and the eye movement begins. At the end of the eye movement, the burst and spread in the fastigial are over.

• Curved Oblique Saccade (MPEG) (5.9 MB)
  This movie shows activity in three cell types in the superior colliculus (fixation, buildup and burst), activity on both sides of the fastigial nucleus, and the eye movement.Prior to a saccade, the fixation cells are active. During a saccade, the activity starts in the buildup neurons, and spreads rapidly to the front of the SC, after which the buildup and burst neurons both burst. At the time of the burst, the activity in the fastigial nuclei begins to spread, and the eye movement begins. At the end of the eye movement, the burst and spread in the fastigial are over. At the beginning of the saccade, the eye movement trajectory is perturbed upward.This causes the activity in the fastigial neurons to move slightly upward relative to the unperturbed case. This drives the eye downward, resulting in a curved trajectory that brings the eye closer to the target.

• Electrical Stimulation of SC producing a staircase of saccades (MPEG) (7.8 MB)
  This movie shows activity in the superior colliculus and the fastigial nucleus. It shows the eye movement as a plot of eccentricity vs. time. At the beginning of the movie, as bright spot of high activity is shown at a caudal site in the superior colliculus.This corresponds to the activity in buildup and burst neurons caused by electrical stimulation with an electrode at that locus. An eye movement begins, and the activity in the fastigial nuclei spreads from its initial site to its final site on the opposite side as the saccade ends.The size of this first saccade is appropriate for the site of activation in the superior colliculus. Because the stimulation continues, another saccade occurs.This causes a repeat of the spread of activity in the fastigial nucleus. For several saccades, this rhythmic cycle of spreading activity occurs over and over. The resulting eye position trace looks like a staircase.However, note that the first step is larger than the subsequent steps.That is because when the first saccade occurs, there is no opposing activity in the opposite fastigial nucleus. However, when the second saccade begins, the inhibitory output from the other fastigial nucleus has not yet decayed to zero.This residual inhibition causes the saccade to be smaller than normal.

Presentations *

• Presentation of 3-D control of eye movements

• Interpreting Neural Data: Maps, Codes and Signals in the Saccadic System

* For Those Using Screen Readers: To obtain these presentations in an accessible format, please contact Dr. Lance Optican lmo@lsr.nei.nih.gov.