Vergence transient component: an index to oculomotor learning modification

Abstract

The brain has a dynamic ability to change or adapt which is imperative for survival of a species. Research has shown that the dynamics of disparity vergence eye movements, the inward (convergence) or outward (divergence) turning of the eyes, are malleable and depend to some extent on the amplitude of preceding stimuli. Disparity convergence is composed of two components. The transient component is open loop and accounts for the system's speed; whereas the sustained component is assumed to be feedback controlled allowing the system to be very accurate. The purpose of this study was to investigate if the modification of convergence eye movements was a function of the magnitude of the subject's transient component. An experimental session consisted of three phases: baseline, modification, and recovery. The baseline and recovery phases used only 4 degrees step test stimuli. The modification phase consisted of a 4 degrees test randomly intermixed with a larger conditioning double step or step ramp stimulus presented in a 1:5 ratio. Eight subjects participated. Independent component analysis was used to decompose the vergence responses into the transient and sustained components. Results show the magnitude of the transient component is an indicator for the amount of dynamic change observed during the modification phase, R = 0.88.