Ruby S Bouhassira¹, Samantha A Montoya¹, Kristina Kitsul¹, Alan A Stocker¹, Geoffrey K Aguirre¹; ¹University of Pennsylvania

While people with migraine and photophobia experience discomfort from bright and flickering lights, there has been limited study of psychophysical discrimination sensitivity in this population. We designed a measure of wide-field flicker frequency discrimination and examined if people with migraine have altered sensitivity, especially for flicker presented at higher light levels. On each of 1600 trials over 4 sessions, participants with migraine with aura and photophobia, and headache-free controls (n=9 and 12, respectively, of 15 planned for each group) viewed simultaneous, achromatic, sinusoidal flicker presented separately to the left and right hemifield of a binocularly fused, dichoptic stimulus field (30° spatially uniform). Participants performed a same/different judgement (ignoring phase) and received auditory feedback. Sessions alternated between a high (~2100 cd/m²) and low (~10 cd/m²) luminance background. High (30%) and low (10%) contrast levels were intermixed. All trials presented one of five reference frequencies (10, 13, 17, 23, 30 Hz) and the test frequency was guided by an adaptive procedure. We estimated internal noise in frequency discrimination by fitting a probabilistic model to the psychophysical data, and then assessing sensitivity across group, reference frequency, contrast, and background luminance conditions. At this intermediate stage of data collection (~2/3 complete), we did not find significant interactions between group and reference frequency, contrast, or light level. Across groups, discrimination was uniformly better at high vs. low contrast (F(1,19) = 43.76, p < 0.001), as expected. Discrimination also improved with increasing reference frequencies, departing modestly from Weber’s law (F(4,76) = 4.00, p = 0.005). Despite experiencing discomfort from flickering stimuli, we find that people with migraine and photophobia are able to discriminate the appearance of flickering stimuli in a manner similar to headache free controls. It remains possible that subtle differences between the groups will be revealed in our final, pre-registered cohort.

Acknowledgements: 1R01EY036255