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B. D. Dornstauder, P. R. Freund, G. S. Gilmour, Y. Sauve; Wavelet Analysis Shows Age-Related Changes in Full Field ERG Oscillatory Potentials in Humans. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1496.
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Oscillatory potentials (OPs) are complex visually elicited field potentials linked to phase-locking of inner retinal cells. To study the impact of age on OPs in healthy humans, we used Morlet wavelet analysis as described for rat ERGs (Forte et al., 2008, J Neurosci
169:191-200).Methods: Photopic and scotopic ERG intensity responses were recorded from healthy individuals aged 20 to <40y (n = 25 mean age 24), 40 to <60y (n = 21 mean age 52), and 60 to <80y (n = 17 mean age 68). Wavelet analysis of human ERG data was performed in MATLAB using a continuous wavelet transform with a complex Morlet wavelet over a frequency range of 50-300Hz. All statistics were performed using a Mann-Whitney U-test (significance at p<0.05).
For all age groups, wavelet amplitudes increased as a function of stimulus intensity, wavelet frequency underwent a mild increase only at high intensity flashes, and scotopic wavelet latencies were increased at intermediate intensities (-3.2 to -2.0 log cds/m2) then declined sharply at higher intensities. Significant age-related changes were observed: 1) Decreased scotopic intensity response wavelet amplitudes in the two older groups (compared to the younger group) for flash intensities of -2.0 to 1.4 log cds/m2; 2) Decreased photopic intensity response amplitudes from -0.4 to 0.9 log cds/m2 in the oldest group (compared to younger groups); 3) Lower transient increase in scotopic latencies in the two older groups (compared to the youngest group); and 4) irregular wavelets in the oldest group. Finally, wavelet frequencies did not change with age.
Wavelet analysis shows that the inner retina undergoes functional changes with age. Changes in the middle age group were only detected under scotopic conditions, suggesting that OP changes are first detected under scotopic conditions. Changes affecting rod bipolar cell coupling onto cone bipolar cells via AII amacrine cells may explain, at least in part, these findings.
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