Neuro-control in divergence eye movements

Vergence eye movements are essential to daily life. When driving down a highway a person typically looks between the speedometer and the road signs. This form of eye movement initiates a vergence response. Vergence is composed of convergence (inward) and divergence (outward) eye movements. Convergence movements are a combination of dual controllers, described as feedforward and feedback components. The feedforward component is a pulse of energy released by burst cells in the initial stage of the eye movement. Feedback is a series of steady periodic pulses released by tonic cells to fixate the eyes onto the target However, divergence eye movements have not been studied extensively in the past. This study will examine the neuro-control strategy used to mediate divergence eye movements (looking from near to far), when given different initial positions for the eyes to begin moving from. Preliminary data using independent component analysis (ICA) shows the divergence system contains an initial pulse, similar to the burst cells found to initiate convergence movements, when the movement began with a large intial bias (target very close to the subject). In responses beginning at a target located further away from the subject and continuing to move farther away, there is no noticeable pulse based on ICA. Demonstrated in this study is the dynamics of divergence movements at different initial conditions.