Effect of stimulus unpredictability in time and magnitude on the vergence system
Tutor / directorPujol Ramo, Jaume
Document typeMaster thesis
Rights accessRestricted access - author's decision
Purpose: To study the influence of stimulus predictability (in magnitude and time) and subject?s expertise in vergence facility test in vergence latency times. Methods: Twenty-seven asymptomatic patients were evaluated during two sessions composed each of them by four experimental conditions. An haploscopic setup was used to present the stimuli with different vergence demands while eye movements were objectively registered with an eye-tracker. One condition tried to replicate the vergence facility clinical test, while the other three introduced a randomness character (in vergence magnitude and/or time) to the initial vergence transitions. Patients were asked to fuse as fast as possible the stimuli presented in each display. Moreover, to test predictability perception, patients were asked to rank the test from ?totally predictable? to ?completely random?. Results: On one hand, neither within-subjects factors condition (p = 0.217), direction (p = 0.132) nor the interaction direction*condition (p = 0.08) did show significant statistical differences in vergence latency. On the other hand, a significant interaction between the direction of the movement and the patients? expertise was found (p = 0.04). Furthermore, in general patients were able to perceive the randomness character of the different conditions (p < 0,001). Conclusions: Expertise was proved to be a key factor reducing latency times especially in convergence transitions and when the character of the test became more random. In addition, predictability was correctly perceived by patients specially when vergence magnitude became more random.
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