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Keiko Momose; Topographic maps of VEP Elicited By Pseudorandom Stimulation with The Swept Parameter Technique. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5716.
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To determine the response function of the human visual magnocellular (M) and parvocellular (P) pathways, topographic maps of VEP kernels was measured. VEPs were elicited by the pseudorandom binary sequence (PRBS) stimulation combined with swept parameter technique and the nonlinear system identification method .
64-channel VEP elicited by luminance modulated sinusoidal gratings based on PRBS was recorded and their first and second-order kernels were calculated as cross-correlation between PRBS and VEP. The spatial frequency of gratings were swept during the PRBS stimulation. VEP to this stimulation was recorded from 3 healthy participants and their changes of binary kernels topogram during the stimulation were evaluated. PRBS stimulation of 40950 ms period was repeated twice, and the spatial frequency was swept from 0.1 to 8 c/deg or 8 to 0.1 c/deg within the period. Stimulation with constant spatial frequency of 1 c/deg and 6 c/deg were also used. The magnitudes of M and P visual pathway responses in VEP was manipulated by sweeping the spatial frequency.
First and second-order binary kernels recorded from the occipital and parietal area was highly dependent on the spatial frequency of the stimulation, especially peaks around 50-200 ms. In addition, their waveforms of the kernels for lower and higher spatial frequency stimulation were similar to those for 1 c/deg and 6 c/deg stimulation, respectively. These waveforms dependency on the spatial frequency sweeping may reflect the M and P pathway contribution. Amplitude of binary kernel recorded from the occipital area was highest and also highly dependent on the spatial frequency of the stimulation, especially peaks around 130 ms (N90-P130-N180). Kernel characteristics of the parieto-occipital area were spread to surrounding areas with decreasing their amplitudes.
Although SNR improvement is required, the topographic maps of VEP kernel would be an index for studying several neuro-cognitive disorders which have been reported to relate with selective damage in M/P pathways.Reference Momose K, Proc. 31th Annu. Conf. the IEEE EMBS (CD-ROM), 2010: 6571-6574.
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