Schematic model of saccade-vergence interactions

The purpose of this study was to determine whether saccadic disconjugacy under the disparity-only condition consistently facilitates the vergence response, and to develop a schematic model of saccade-vergence control to account for the present as well as previous results. Vertical line targets on two oscilloscope screens were presented dichoptically to the eyes using horizontal step displacements of various amplitudes. Binocular horizontal eye movements were recorded using the infrared reflection technique in five normal subjects. The experimental results showed an approximately equal distribution of facilitation and disfacilitation by the disconjugate saccades. This indicated that with disparity-only stimulation, in the absence of absolute depth and blur cues, there was no consistent enhancement of the vergence response. The schematic model showed that sequential and simultaneous onset of the disjunctive and conjugate controller signals resulted in non-facilitation and facilitation, respectively, of the ongoing movement. Thus, the model was able to account for the present results under the disparity-only condition as well as previous results under the rich-stimulus-cues condition.