The effect of migraine diagnosis upon pupil responses to illusory brightness

• Compared to Uniform (6.2%), there were greater responses to the Glow (8.7%, t[44 df] = 3.14; p = 0.003) and Halo (8.0%, t[44] = 2.21; p = 0.032) stimuli. • Glow and Halo responses were not significantly different (t[44] = 0.95; p = 0.347) • Glow vs. Uniform responses were not reliably different in MwA compared to HaF subjects (t[28] = 0.84; p = 0.41). Previous work has found that the pupil constricts to illusory brightness, presumably mediated by a cortical mechanism (Laeng 2012). Photophobia, a common symptom of migraine, results in lowered thresholds for discomfort from light. While people with MwA do not have an altered amplitude of pupil response to uniform pulses of light, they do have increased reports of discomfort (McAdams 2020), and enhanced cortical responses to visual stimulation (Datta 2013). If illusory brightness causes pupil constriction on the basis of cortical processing, and people with MwA have enhanced cortical responses to visual stimuli, it may be the case that there is an enhanced pupil response to illusory brightness in MwA, but not in MwoA, or in HaF controls. In a preregistered study (github.com/gkaguirrelab/preregistrations) we examined if people with MwA, as compared to other populations, have an enhanced pupil response to illusory brightness induced by border contrast or a “glow” profile (Tamura 2016).