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G. S. Souza, B. D. Gomes, E. M. C. B. Lacerda, C. A. Saito, M. da Silva Filho, L. C. L. Silveira; Physiological Correlations Among Pattern Visual Evoked Potential Components Based in Their Contrast Sensitivity. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3313. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare contrast sensitivity values obtained with transient visual evoked potential (tVEP) elicited by achromatic pattern reversal or pattern onset / offset stimulation by measuring the amplitude of different tVEP components (P100 and N135 for pattern reversal and C1 and C2 for pattern onset / offset presentations).
We measured 12 young adult subjects (6 males, 22.9 ± 2.6 years old). Visual stimuli were 2 cpd sinewave achromatic horizontal gratings monocularly presented in a circle of 5º diameter. Two stimulus configurations were used: 1 Hz pattern reversal presentation; and 300 ms onset / 700 ms offset presentation. Contrast thresholds were estimated by fitting straight lines to data points representing tVEP amplitude at different log contrasts and extrapolating these lines to the zero amplitude level.
For the achromatic pattern reversal presentation, a double slope function described the P100 amplitude - log contrast relation, which had a limb at high contrast and another limb at medium-to-low contrasts. The N135 amplitude - log contrast function was well described by single straight-lines. For the achromatic onset / offset presentation, C1 and C2 amplitudes increased monotonically as contrast is increased and single straight lines described the tVEP amplitude versus contrast functions in the medium-to-low contrast range, but C2 amplitude saturated at high contrasts. High contrast sensitivity was obtained using middle-to-low contrast data for P100, N135, and C2 with no statistical difference between them (ANOVA, Tukey test, p < 0.05), whilst C1 and high contrast data for P100 returned low contrast sensitivity values.
We suggest that at 2 cpd a high contrast sensitivity mechanism driven by the M pathway contributes to the P100 component at medium-to-low contrasts and to the N135 and C2 components at all contrast levels.
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