Visual noise selectively degrades vision in migraine.

Purpose. Migraine is a disabling condition with underlying neuronal mechanisms that remain elusive. Migraineurs experience hyperresponsivity to visual stimuli and frequently experience visual disturbances. In the present study, the equivalent input noise approach was used to reveal abnormalities of visual processing and to isolate factors responsible for any such deficits. This approach partitions visual sensitivity into components that represent the efficiency of using the available stimulus information, the background internal noise due to irregular neuronal fluctuations, and the neuronal noise induced by the external stimulation. Methods. Ten migraine with aura, ten migraine without aura, and ten age-matched headache-free subjects participated. Performance in detecting luminance targets embedded in visual noise, resembling grainy photographs, was measured at various noise levels. Results. Contrast thresholds of the three subject groups were similar in the absence of noise, but both migraine groups performed worse in the presence of high noise levels, with performance of migraineurs with aura significantly poorer (P < 0.05) than that of control subjects. Data were fitted with a perceptual template model that showed that the model parameter determining the internal (neuronal) noise triggered by the external (stimulus) noise was significantly higher (P < 0.001) in both migraine groups than in the non-migraineur group. Migraineurs without aura also showed a significant (P < 0.05) though weak reduction of sampling efficiency (0.12 +/- 0.02) compared with control subjects (0.17 +/- 0.02). Conclusions. The results revealed substantial external noise-exclusion deficits in migraine with aura and a minor impairment of noise exclusion in migraine without aura. Migraineurs appeared prone to abnormally high variability of neuronal activity. This result provides a promising explanation of observed visual deficits in migraine.