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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:37 |
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Conference: Bucharest University Faculty of Physics 2013 Meeting
Section: Theoretical Physics and Applied Mathematics
Title:
Dynamical complexity analysis of saccadic eye movements in two different physiological conditions
Authors:
Corina Astefănoaei(1), Dorina Creanga(1), Elena Pretegiani(2), Lance M. Optican(3), Alessandra Rufa(2)
Affiliation:
(1)Faculty of Physics, Laboratory of Biophysics & Medical Physics, University “Alexandru Ioan Cuza”, 11 Bd. Carol I, 700506, Iasi, Romania
(2) Eye-tracking &Visual Application Lab EVALab, Department of Medicine Surgery and Neuroscience, University of Siena, Siena 53100, Italy
(3) Laboratory of Sensorimotor Research, National Eye Institute, Bethesda, MD, 20892, USA
E-mail
corina_astefanoaei@yahoo.com
Keywords:
saccades, complex dynamics, signal processing
Abstract:
Eye movement represents a challenging domain for multidisciplinary research focused on visuo-spatial exploration. Semi-quantitative parameters and qualitative tests application to eye movement signals may provide important information on neuro-visual system, since computational approach is an alternative way in understanding brain functioning; also, the presence of atypical response to computational test of eye movement temporal series may be the indicator of specific pathology. Saccadic eye movements of normal subject were assessed through semi-quantitative analysis based on linear and non-linear processing tests in order to highlight the type of system evolution. Saccades are eye movements redirecting rapidly the fovea to visual targets. These movements were recorded during simple saccade test and respectively, cognitive load visually-guided one using an infrared eye tracking system in special experimental arrangement that includes gaps and overlaps between the appearance of the visual stimuli; the visual stimuli were two red dots projected onto a translucent screen placed in front of the subject’s eyes – one fixed point, acting as central fixation point for the subject and the other one (the target) that could be moved at the left or at the right of the fixation point. The collected signals were investigated comparing normal and cognitive load situation (which means saccade execution and decision by button pressing), considering both raw and numerical smoothed data. Power spectrum, autocorrelation function and autocorrelation time, the phase-space reconstruction, the correlation dimension Hurst exponent and Lyapunov exponent were applied for the diagnosis of saccadic system dynamics. Following the application of these specific tests, similar responses were obtained, with chaotic dynamical trend dominancy. It seems that complex dynamics characterizes neuro-visual system involved in saccade preparation, triggering and accomplishment; identifying the biophysical processes underlying the generation and propagation of neural impulses that are mainly responsible for complex chaotic dynamics is the next objective in developing this study.
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