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M. Kirzhner, J.N. Nam, C.J. Clemens, K. Holopigian; The Retinotopic Distribution of Localized Attention Assessed Using the Multifocal Visual Evoked Potential . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4125.
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Purpose: Previously, we have demonstrated enhancement of multifocal visual evoked potential (mfVEP) amplitudes when the attentional demands of the stimulus were increased (Seiple et al, 2002). However, this study only examined effects along 1 meridian. In the present study, we examined the distribution of attention-related enhancement throughout the visual field using the mfVEP. Methods: mfVEPs were obtained from normally sighted subjects who were refracted to 20/20 acuity at the viewing distance of 32 cm. The stimulus array consisted of 16-scaled sectors that pattern-reversed according to a pseudorandom (m) sequence. The display had a diameter of 40°. Electrodes were placed on the mid-line and a forehead electrode served as the ground. On separate trials, subjects were instructed to fixate the center with no specific attentional task, or to fixate the center and count the number of laser LED flashes presented in a specific quadrant of the display. Peak-to-peak amplitudes of the second order response were measured using the VERIS software. Results:Response amplitudes for each sector were compared between attended and non-attended conditions. mfVEP amplitudes were increased in the attended quadrant. The magnitude of the attention-related amplitude enhancements varied as a function of position in the visual field. Conclusions: Local attention-related enhancements in electrophysiological responses can be observed using the mfVEP.
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