Fractal Dimension Analysis of Transient Visual Evoked Potentials: Optimisation and Applications

被引:6
作者
Boon, Mei Ying [1 ]
Henry, Bruce Ian [2 ]
Chu, Byoung Sun [1 ,6 ]
Basahi, Nour [1 ]
Suttle, Catherine May [1 ,7 ]
Luu, Chi [3 ,4 ]
Leung, Harry [5 ,8 ]
Hing, Stephen [5 ]
机构
[1] UNSW Australia, Sch Optometry & Vis Sci, Sydney, NSW, Australia
[2] UNSW Australia, Sch Math & Stat, Sydney, NSW, Australia
[3] Royal Victorian Eye & Ear Hosp, Ctr Eye Res Australia, East Melbourne, Vic, Australia
[4] Univ Melbourne, Melbourne Med Sch, Dept Surg Ophthalmol, Parkville, Vic, Australia
[5] Pk Rd Eye, Hurstville, NSW, Australia
[6] Catholic Univ Daegu, Sch Optometry & Vis Sci, Gyeongsangbuk Do, South Korea
[7] City Univ London, Sch Hlth Sci Optometry & Visual Sci, London, England
[8] Southern Ophthalmol, Kogarah, NSW, Australia
关键词
VEP; DYNAMICS; REVERSAL; CHILDREN;
D O I
10.1371/journal.pone.0161565
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Purpose The visual evoked potential (VEP) provides a time series signal response to an external visual stimulus at the location of the visual cortex. The major VEP signal components, peak latency and amplitude, may be affected by disease processes. Additionally, the VEP contains fine detailed and non-periodic structure, of presently unclear relevance to normal function, which may be quantified using the fractal dimension. The purpose of this study is to provide a systematic investigation of the key parameters in the measurement of the fractal dimension of VEPs, to develop an optimal analysis protocol for application. Methods VEP time series were mathematically transformed using delay time, tau, and embedding dimension, m, parameters. The fractal dimension of the transformed data was obtained from a scaling analysis based on straight line fits to the numbers of pairs of points with separation less than r versus log(r) in the transformed space. Optimal tau, m, and scaling analysis were obtained by comparing the consistency of results using different sampling frequencies. The optimised method was then piloted on samples of normal and abnormal VEPs. Results Consistent fractal dimension estimates were obtained using tau = 4 ms, designating the fractal dimension = D-2 of the time series based on embedding dimension m = 7 (for 3606 Hz and 5000 Hz), m = 6 (for 1803 Hz) and m = 5 (for 1000Hz), and estimating D-2 for each embedding dimension as the steepest slope of the linear scaling region in the plot of log(C(r)) vs log(r) provided the scaling region occurred within the middle third of the plot. Piloting revealed that fractal dimensions were higher from the sampled abnormal than normal achromatic VEPs in adults (p = 0.02). Variances of fractal dimension were higher from the abnormal than normal chromatic VEPs in children (p = 0.01). Conclusions A useful analysis protocol to assess the fractal dimension of transformed VEPs has been developed.
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页数:21
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