Effect of Contrast, Stimulus Density, and Viewing Distance on Multifocal Steady-State Visual Evoked Potentials (MSVs)

Siti N. Abdullah, Nada Aldahlawi, Yanti Rosli, Vaegan, Mei Ying Boon, Ted Maddess
2012 Investigative Ophthalmology and Visual Science  
PURPOSE. We investigated the effects of image contrast, stimulus density, and viewing distance upon a multifocal steady-state visual evoked potential (MSV) method. METHODS. Fourteen adults with normal vision (mean age ¼ 27.0 6 6.6 years; 6 males) participated in the study. Each of the stimulus regions of the multifocal ensembles presented a contrast modulated grating, displaying spatial and temporal frequencies that evoke the spatial frequency doubling illusion. All subjects were tested at five
more » ... were tested at five contrasts: 0.06, 0.11, 0.22, 0.45, and 0.89; viewed at 16, 32, and 128 cm. A multivariate linear model estimated factors for each stimulus region, recording channel, number of stimuli (9 or 17 regions), and sex; and covariates for contrast, and octaves of viewing distance, and age. RESULTS. The responses per unit area for the 17-region display were significantly larger than for the 9-region display (P < 10 À12 ). The contrast-response function could be described by a power law with exponent 0.068 (P < 0.008). The effect of viewing distance was small but significant: response amplitude dropped by À0.17 6 0.03 dB per octave of viewing distance (P < 10 À6 ), or 10% over 8 octaves.
doi:10.1167/iovs.11-9325 pmid:22786904 fatcat:bj2icr2akrg6liyhg76hygoo2y