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H. A. Hancock; Wavelet Analysis of Oscillatory Potentials in Humans. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1516.
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To explore the relationship of the amplitude vs intensity and timing versus intensity for each of the first four peaks of the human oscillatory potential.
ERGs were recorded using different intensities covering 0.025 to 40 candela.s.m2, this is a factor of 10 above and below the standard OPs flash intensity. Five human subjects who were free of known ocular pathologies were tested. OPs were isolated by band-pass filtering between 100-300Hz. The amplitude and implicit time of each of the first four OP wavelets were measured and plotted individually versus stimulus intensity.
OP 2 and 3 are the largest in amplitude. They exhibited a similar pattern when wavelet amplitude is plotted versus log intensity, peaking near 1 cd.s.m.2 OP 1 reached its half-maximal amplitude at a higher light intensity than OPs 2 , 3 or 4. When timing was plotted versus log stimulus intensity, all of the individual OP curves were similar with essentially linear declines in time to peak with increases of stimulus strength.
Analysis of the individual peaks of the oscillatory potentials reveal that the behavioral characteristics of individual waveforms match that of the lumped or summed responses. More light is required to generate the half-maximal response for OP 1. Each OP wavelet demonstrated a peaked function when amplitude was plotted versus stimulus intensity, similar to a photopic hill.
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