Instrumentation to study the influence of attention on disparity vergence: Design of novel central and peripheral stimuli

The study of saccades (side to side eye movements) with various types of visual fields or distracters has lead to a deeper understanding of the mechanisms of attention. Yet, virtually no research exists on how the influence of attention modulates the neural control of disparity vergence, the inward or outward turning of the eyes to view targets in depth. Within our activities of daily living, we use a combination of eye movements including vergence and saccades to acquire visual information. This investigation describes instrumentation to systematically study the influence of attention on disparity vergence. Disparity vergence can be modeled as a preprogrammed coupled with a feedback component describing the system's speed and accuracy respectively. Hence, two types of central stimuli were generated: a step stimulus which predominantly evokes the preprogrammed component during the transient portion of the movement and a ramp stimulus to study changes within the feedback component. To stimulate only disparity while keeping accommodation constant, the system was designed using a haploscope configuration. Four types of periphery stimuli were generated that vary the amount and type of distracters. The influence of attention, or the effect of the peripheral stimulation, will be assessed by quantifying peak velocities and error defined as the difference between the stimulus and vergence eye movement response. Preliminary results show that central and peripheral visual stimuli can be programmed independently and this system can be utilized to systematically study the influence of different types of distracters on disparity vergence responses. Future directions include further data collection and analysis in healthy control and those from neurological dysfunctional populations.