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. 2008 Aug;34(3-4):381-92.
doi: 10.1007/s10867-008-9092-1. Epub 2008 Jul 24.

Eye-target Synchronization in Mild Traumatic Brain-Injured Patients

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Free PMC article

Eye-target Synchronization in Mild Traumatic Brain-Injured Patients

R Contreras et al. J Biol Phys. .
Free PMC article

Abstract

Eye-target synchronization is critical for effective smooth pursuit of a moving visual target. We apply the nonlinear dynamical technique of stochastic-phase synchronization to human visual pursuit of a moving target, in both normal and mild traumatic brain-injured (mTBI) patients. We observe significant fatigue effects in all subject populations, in which subjects synchronize better with the target during the first half of the trial than in the second half. The fatigue effect differed, however, between the normal and the mTBI populations and between old and young subpopulations of each group. In some cases, the younger (<or=40 years old) normal subjects performed better than mTBI subjects and also better than older (>40 years old) normal subjects. Our results, however, suggest that further studies will be necessary before a standard of "normal" smooth pursuit synchronization can be developed.

Figures

Fig. 1
Fig. 1
Target path (red dots) and eye position (blue, left eye; black, right eye) for a normal subject (a) and a TBI patient (b) during one full cycle of target tracking. Gaps in the eye position path are due to blinking
Fig. 2
Fig. 2
Phase differences between eye and target for normal (a) and TBI (c) subjects. The corresponding phase difference histograms are shown in b and d
Fig. 3
Fig. 3
Angular velocity (a) and phase difference (b) as a function of time for the same subject
Fig. 4
Fig. 4
Distributions of synchronization indices for normal subjects, divided into age groups and with the first and second halves of each trial separated. The top row (a and b) shows younger subjects (<40 years old); the bottom row (c and d) shows older subjects (>40 years old). The left-hand panels (a and c) show synchronization in the first half of each trial, while the right-hand panels (b and d) show synchronization in the second half
Fig. 5
Fig. 5
Distributions of synchronization indices for TBI patients. Contrary to normal subjects (see Fig. 4), younger and older TBI patients do not show a marked difference
Fig. 6
Fig. 6
The percentage drop in synchronization index between the first and second half of each trial is illustrated as a function of age for normal subjects (a, young group; c, older group) and for TBI patients (b, young group; d, older group). Note the data from the two “outlier” young normal subjects, circled in a

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