title: EYE MOVEMENT RECORDING AND NONLINEAR DYNAMICS ANALYSIS - THE CASE OF SACCADES.
abstract: Evidence of a chaotic behavioral trend in eye movement dynamics was examined in the case of a saccadic temporal series collected from a healthy human subject. Saccades are highvelocity eye movements of very short duration, their recording being relatively accessible, so that the resulting data series could be studied computationally for understanding the neural processing in a motor system. The aim of this study was to assess the complexity degree in the eye movement dynamics. To do this we analyzed the saccadic temporal series recorded with an infrared camera eye tracker from a healthy human subject in a special experimental arrangement which provides continuous records of eye position, both saccades (eye shifting movements) and fixations (focusing over regions of interest, with rapid, small fluctuations). The semi-quantitative approach used in this paper in studying the eye functioning from the viewpoint of non-linear dynamics was accomplished by some computational tests (power spectrum, portrait in the state space and its fractal dimension, Hurst exponent and largest Lyapunov exponent) derived from chaos theory. A high complexity dynamical trend was found. Lyapunov largest exponent test suggested bi-stability of cellular membrane resting potential during saccadic experiment.
authors.affiliation: Laboratory of Biophysics & Medical Physics, Faculty of Physics, "Alexandru Ioan Cuza" University, 11, Carol I Blvd., 700506, Iași, Romania.
authors.forename: Corina
authors.initials: C
authors.lastname: Aştefănoaei
authors.affiliation: Eye-tracking & Visual Application Lab EVALab, Department of Medicine Surgery and Neuroscience, University of Siena, Siena 53100, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Pretegiani
authors.affiliation: Laboratory of Sensorimotor Research, National Eye Institute, Bethesda, MD, 20892, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Optican
authors.affiliation: Laboratory of Biophysics & Medical Physics, Faculty of Physics, "Alexandru Ioan Cuza" University, 11, Carol I Blvd., 700506, Iași, Romania.
authors.forename: Dorina
authors.initials: D
authors.lastname: Creangă
authors.affiliation: Eye-tracking & Visual Application Lab EVALab, Department of Medicine Surgery and Neuroscience, University of Siena, Siena 53100, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Rufa
keywords: complex dynamics; eye movement control; saccade