Electro-oculography of saccades to flashed targets

Abstract

The nature of the saccadic control by hemispherical structures remains controversial. Experimental and clinical studies suggest that velocity data are available at the superior colliculus. This study searches for clinical situations with a dissociation between saccadic amplitude and velocity coding. The velocity-amplitude relationship (VAR) of saccades evoked by flashed and long-drawn targets are compared. In the control group, the use of flashed targets fails to modify this relationship but decreases the accuracy of the saccades which become hypo- or hypermetric. Supra-collicular lesions may impair the VAR and the use of flashed targets reveals this defect more efficiently. Modification of the VAR by supra-collicular lesions could result either from an insufficient activation of the deep collicular cells, or from a lack of inhibition of the pause cells as simulated on a theoretical model.

Key Words:

• eye movements
• saccades
• electro-oculography
• superior colliculus
• hemispheric lesions
• biological models