Modelling contrast discrimination data suggest both the pedestal effect and stochastic resonance to be caused by the same mechanism

Abstract

Computational models of spatial vision typically make use of a (rectified) linear filter, a nonlinearity and dominant late noise to account for human contrast discrimination data. Linear-nonlinear cascade models predict an improvement in observers' contrast detection performance when low, subthreshold levels of external noise are added (i.e., stochastic resonance). Here, we address the issue whether a single contrast gain-control model of early spatial vision can account for both the pedestal effect, i.e., the improved detectability of a grating in the presence of a low-contrast masking grating, and stochastic resonance. We measured contrast discrimination performance without noise and in both weak and moderate levels of noise. Making use of a full quantitative description of our data with few parameters combined with comprehensive model selection assessments, we show the pedestal effect to be more reduced in the presence of weak noise than in moderate noise. This reduction rules out independent, additive sources of performance improvement and, together with a simulation study, supports the parsimonious explanation that a single mechanism underlies the pedestal effect and stochastic resonance in contrast perception.

Low Intensity TMS Enhances Perception of Visual Stimuli

“…However, pedestals above the detection threshold are subject to Weber's law that requires increasingly high discrimination thresholds and produce masking rather than a pedestal effect. This description of the effect of TMS as a noisy pedestal is equivalent to the description offered by Schwarzkopf et al [6] in terms of stochastic resonance [29,30]. However, it is possible that due to different qualitative effects of low and high intensity TMS, the underlying shape of the transducer function can have an atypical form compared to those reported in vision experiments.…”

Steady-State Contrast Response Functions Provide a Sensitive and Objective Index of Amblyopic Deficits

“…36 Dichoptic facilitation has also been reported, 28,37 though this is typically very weak (threshold improvements of less than a factor of two), and occurs at pedestal contrasts much lower than the 26% contrast mask used here. Although it is conceivable that amblyopes might experience abnormal levels of dichoptic facilitation that could overcome interocular suppression, there is no evidence of this in studies measuring detection thresholds in the presence of dichoptic masks.…”

The effect of notched noise on flicker detection and discrimination

“…In spatial vision, the depth of the dipper and the location of its minimum depend on performance level: the dipper exhibited for low performance levels is deeper and occurs at higher pedestal levels than the dipper exhibited for higher performance levels (Bird et al, 2002;Goris, Wagemans, & Wichman, 2008;Wichmann, 1999). Similarly, for flicker, we find that the maximum improvement with added pedestal modulation is greater at lower than at higher performance levels and tends to occur at slightly higher pedestal modulations.…”