Application of the System Identification Technique to Goal-Directed Saccades.

Abstract

Abstract : Saccadic eye movements are among the fastest voluntary muscle movements the human body is capable of producing and are characterized by a rapid shift of gaze from one point of fixation to another. Although the purpose for such an eye movement is obvious (that is, to quickly redirect the eyeball to the target), the neuronal control strategy is not. The present investigation utilizes system identification techniques to estimate muscle forces during horizontal saccadic eye movements in order to better understand the neuronal control strategy. The lateral and medial rectus muscle of each eye was modeled as a parallel combination of an active state tension generator with a viscosity and elastic element, connected to a series elastic element. The eyeball was modeled as a sphere connected to a viscosity and elastic element. The predictions of the model were shown to be in good agreement with the data. The results of extensive analysis did not support the existence of a postulated continuous-time external feedback control mechanism. Analysis of the data, however, did support a time optimal control strategy, a strategy which directs the eyeball to its destination in minimum time for saccades of all sizes. Keywords include: Linear homeomorphic model, Neuronal control strategy, Oculomotor plant, Fourier transform, and Laplace transform.