A comparison of dynamics in convergence and divergence eye movements

The details in timing and dynamics of inward (convergence) and outward (divergence) turning eye movements (vergence eye movements) were compared. Experiments showed that there were significant differences in the timing characteristics of convergence versus divergence movements. A model-based analysis showed that the dynamics were also different in these two vergence eye movements. Based on the assumption that these movements are driven by a neural signal composed of a pulse and a step, the gain ratio between pulse and step components was much larger than one for convergence responses, but was close to or less than one in divergence responses. These data indicate that the neural control signal for divergence is close to a simple step rather than the combined pulse-step signal in convergence.