Reducing luminance intensity can improve motion perception in noise

Rémy Allard,Angelo Arleo

doi:10.1038/srep43140

Abstract

Visual perception generally improves under brighter environments. For instance, motion sensitivity is known to improve with luminance intensity especially at high temporal frequencies. However, the current study counter-intuitively shows that increasing luminance intensity can impair motion sensitivity in noise. Motion sensitivity was measured with and without noise added to a drifting Gabor patch as a function of the temporal frequency and luminance intensity. As expected, motion sensitivity in absence of noise reached a ceiling performance at a relatively low luminance intensity (about 35 td) for low temporal frequencies and improved with luminance intensity up to the highest luminance intensity tested (353 td) for high temporal frequencies. In noise, reducing mean luminance intensity facilitated motion sensitivity (up to a factor of about 1.7) for temporal frequencies up to 7.5 Hz and impaired sensitivity at higher temporal frequencies (15 and 30 Hz). We conclude that reducing luminance intensity is effectively equivalent to applying a low-pass filter, which can improve motion sensitivity in noise to low and middle temporal frequencies. This counterintuitive facilitation effect can be explained by two known properties of the visual system: decreasing luminance intensity impairs the visibility of high temporal frequencies (equivalent to a low-pass filter) and motion detectors are broadly tuned.

Highlights

Visual perception generally improves under brighter environments
In a recent study[1], we found that artificially applying a temporally low-pass filter to the stimulus could improve motion sensitivity in white noise at low and middle temporal frequencies
At low temporal frequencies, sensitivity was independent of luminance intensity (i.e., Weber law) at high luminance intensities, whereas at high temporal frequencies, sensitivity depended on luminance intensity at all luminance intensities

Summary

Introduction

Visual perception generally improves under brighter environments. For instance, motion sensitivity is known to improve with luminance intensity especially at high temporal frequencies. We conclude that reducing luminance intensity is effectively equivalent to applying a low-pass filter, which can improve motion sensitivity in noise to low and middle temporal frequencies. In a recent study[1], we found that artificially applying a temporally low-pass filter to the stimulus (which reduces the effective contrast at high temporal frequencies) could improve motion sensitivity in white noise at low and middle temporal frequencies. As a result, reducing luminance intensity should be equivalent to applying a low-pass filter (reduce the effective contrast of high temporal frequencies), which leads to the counter-intuitive prediction that reducing luminance intensity (e.g., by wearing sunglasses) could improve motion sensitivity in high noise at low and middle frequencies. The current study evaluated motion sensitivity (i.e., contrast threshold using direction discrimination task) at various temporal frequencies and luminance intensities in absence of noise and in high noise

Methods

Results

Conclusion