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X. Zhang, M.Y. Chee, D.C. Hood; Isolation of a V1 Component from the Multifocal VEP: Contributions from M and P Pathways . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4197.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To derive a V1 component from multifocal VEP (mfVEP) responses with a combination of the principle component analysis (PCA) and a new mfVEP paradigm and to examine the contributions from M and P pathways. Methods: Exp. 1: existing mfVEP data  were analyzed with PCA. Exp. 2: the properties of the principle components (PC) were examined using both achromatic and iso-luminant stimuli with varying contrasts. Monocular mfVEPs were obtained using a dartboard array of 18 locations, 45 deg. in dia., and a new mfVEP paradigm , which allows the simultaneous derivation of the luminance, temporal interaction and spatial interaction VEP kernels. PCs were derived from these kernels. For both experiments, electrodes were placed at the inion (I), 4 cm above I, and 1 cm above and either 4cm to the left or the right of I. Results: Exp. 1: the largest three PCs account for 60%, 20% and 5%, respectively, of the variance. The 1st principle component (PC1) appeared to be generated strictly in the calcarine fissure and presumably, in V1. Only PC1 and PC3 reversed polarity across the horizontal meridian when recorded from vertical channel and across the vertical meridian when recorded from horizontal channel. Exp. 2: The contrast response functions were different from those obtained with either conventional VEP  or standard mfVEP [4,5] recording. The achromatic contrast function of the luminance kernel was monotonic, while there was no response for the iso-luminant luminance kernel. The achromatic contrast function of the temporal interaction kernel saturated at low contrast (50% of max (C50)<8%). The achromatic contrast response function of the spatial interaction kernel saturated at a higher contrast (C50 between 8 and 16%) while the iso-luminant function of this kernel did not saturate. Conclusions: A V1 component can be derived from mfVEPs with PCA. By separating the contributions of luminance, temporal and spatial changes, a mfVEP kernel associated with each of the events can be derived. The achromatic temporal interaction VEP is largely a M pathway response and the iso-luminance spatial interaction largely a P pathway response. 1. Hood et al., (2002) AO. 2. Zhang (2002) ARVO. 3. Rudvin et al. (2000) VNS. 4. Klistorner et al. (1997) VR. 5. Baseler and Sutter (1997) VR.
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