Detection and discrimination of flicker contrast in migraine

Abstract

Aims: Flickering light is strongly aversive to many individuals with migraine. This study was designed to evaluate other abnormalities in the processing of temporally modulating visual stimulation.Methods: We measured psychophysical thresholds for detection of a flickering target and for the discrimination of suprathreshold flicker contrasts (increment thresholds) in 14 migraineurs and 14 healthy controls with and without prior adaptation to high-contrast flicker. Visual discomfort (aversion) thresholds were also assessed.Results: In the baseline (no adaptation) conditions, detection and discrimination thresholds did not differ significantly between groups. Following adaptation, flicker detection thresholds were elevated equivalently in both groups; however, discrimination thresholds were more strongly affected in migraineurs than in controls, showing greater elevation at moderate contrasts and greater threshold reduction (sensitisation) at high contrast (70%). Migraineurs also had significantly elevated discomfort scores, and these were significantly correlated with number of years with migraine.Discussion: We conclude that visual flicker not only causes discomfort but also exerts measurable effects on contrast processing in the visual pathways in migraine. The findings are discussed in the context of the existing literature on habituation, adaptation and contrast-gain control.

The locus of flicker adaptation in the migraine visual system: A dichoptic study

“…The present study once again confirms previous measures from our lab (5,7,8) that flicker is a strongly aversive stimulus to individuals with migraine. While nearly all migraine and very few control participants showed aversion responses on our task, we did not find a significant correlation between the aversion thresholds and the contrast increment thresholds among migraineurs.…”

“…All statistical analyses were conducted using SPSS statistical software (IBM Company, SPSS Inc, 2007). Each participant's aversion threshold scores on the Flicker Aversion Test were averaged across five trials and converted to a discomfort score using the formula: discomfort score = log (1/average aversion threshold) (8). This transforms the aversion thresholds to a discomfort scale on which 0 indicates no aversion or discomfort at all, 1 represents discomfort at 0.10 (10%) contrast and 2 would indicate a very high level of discomfort (0.01 (1%) contrast threshold).…”

Global Shape Processing Deficits Are Amplified by Temporal Masking in Migraine

“…The typical adaptation effect of decreased sensitivity following adaptation to a high contrast flicker was seen for normals and migraineurs when tested with low contrasts. 48 However, following adaption migraineurs showed the opposite effect for high contrast: increased contrast sensitivity. This facilitation effect was not observed in controls.…”

“…It may be that the same processes underlie the deficiencies measured psychophysically and with VEPs. 48 Repeated exposure to the shapes in our experiment is inevitable and the possibility of this resulting in adaptation effects must be considered. Individuals ran different conditions (with and without mask as well as different SOAs) in different blocks.…”

Motion processing deficits in migraine are related to contrast sensitivity

“…Apparently impaired global motion discrimination could, for example, reflect dysfunction that occurs earlier in the visual pathways than in the extrastriate cortex. The importance of taking into account explanations of deficits in migraine at all levels of the visual system, even as early as the retina, has been emphasised by the recent findings of Karanovic et al (8). They investigated detection and discrimination of flicker contrast in migraine, and compared these data with measures of visual discomfort, binocular acuity and refractive errors in each eye.…”