Visual discomfort and flicker

Abstract

Flickering lights can be uncomfortable to look at and can induce seizures in observers with photosensitive epilepsy. However, the temporal characteristics contributing to these effects are not fully known. In the spatial domain, one identified source of visual discomfort is when images have Fourier amplitude spectra that deviate from the natural (~1/frequency, 1/f) statistical characteristics of natural scenes, especially if they contain excess energy at the medium frequencies at which the visual system is most sensitive. We tested for analogous effects in the temporal domain, manipulating both the amplitude and phase spectra of the flicker. Participants judged the relative discomfort of temporal luminance variations in a pair of uniform 17° fields with different temporal modulations. In general, discomfort increased with deviations from natural amplitude spectra, particularly those with excess energy at medium frequencies or biased toward sharper spectra. These ratings of discomfort were also consistent with ratings of how natural the modulations appeared. However, the temporal discomfort judgments were also strongly affected by the phase spectra of the flicker, with fixed vs. random spectra producing very different responses. This was not due to the perceived regularity or predictability of the flicker, but could arise from a number of other potential factors. Our findings suggest that, like spatial patterns, visual discomfort in time-varying patterns depends in part on how similar they are to the amplitude spectra of temporal variations in the natural visual environment, but also point to the critical role of the phase spectrum in the perceived discomfort of flicker.

A neural correlate of visual discomfort from flicker

“…This view is consistent with a growing body of literature that has found that stimuli are perceived as unpleasant when their spatial and temporal content departs from the statistics of natural environments (Juricevic et al, 2010;Penacchio & Wilkins, 2015;Yoshimoto et al, 2017). The visual system is remarkably adaptive across long and short time scales, and an important function of that adaptation is to allow neurons to encode sensory information using a range of representation that is well matched to the current statistics of the environment (Barlow, 2001).…”

“…These findings have led to the general proposal that visually uncomfortable stimuli are the result of "excessive" cortical activity (Aurora & Wilkinson, 2007). This account finds further support in the observation that people with migraine have both greater discomfort from flickering light (Yoshimoto et al, 2017) and an enhanced visual cortex response to these stimuli (Datta, Aguirre, Hu, Detre, & Cucchiara, 2013;Shibata, Yamane, Nishimura, Kondo, & Otuka, 2011).…”

Cortical Hyper‐Excitability in Migraine in Response to Chromatic Patterns

“…60,61 If visual processing is impacted negatively, then it is likely that this has an impact on more complex sensory-related processing. For example, flickering fluorescent lighting has been identified as a prime example.…”

Neural, functional, and aesthetic impacts of spatially heterogeneous flicker: A potential role of natural flicker

“…This method generated flicker with spectral amplitude profiles approximating 1/f (except that the maximum flicker rate was 30Hz due to the use of a 60Hz display monitor). We chose this flicker-generating method partly because foveal luminance changes during a typical human experience follow a 1/f profile (van Hateren & van der Schaaf, 1996) and partly because 1/f flicker tends to be perceived as "less uncomfortable" than flicker with profiles deviating from 1/f (Yoshimoto et al, 2017).…”