Cortical Hyper-Excitability in Migraine in Response to Chromatic Patterns.

Objective: Individuals with migraine exhibit heightened sensitivity to visual input that continues beyond their migraine episodes. However, the contribution of color to visual sensitivity, and how it relates to neural activity, has largely been unexplored in these individuals.

Background: Previously, it has been shown that, in non-migraine individuals, patterns with greater chromaticity separation evoked greater cortical activity, regardless of hue, even when colors were isoluminant. Therefore, to investigate whether individuals with migraine experienced increased visual sensitivity, we compared the behavioral and neural responses to chromatic patterns of increasing separation in migraine and non-migraine individuals.

Methods: Seventeen individuals with migraine (12 with aura) and 18 headache-free controls viewed pairs of colored horizontal grating patterns that varied in chromaticity separation. Color pairs were either blue-green, red-green, or red-blue. Participants rated the discomfort of the gratings and electroencephalogram was recorded simultaneously.

Results: Both groups showed increased discomfort ratings and larger N1/N2 event-related potentials (ERPs) with greater chromaticity separation, which is consistent with increased cortical excitability. However, individuals with migraine rated gratings as being disproportionately uncomfortable and exhibited greater effects of chromaticity separation in ERP amplitude across occipital and parietal electrodes. Ratings of discomfort and ERPs were smaller in response to the blue-green color pairs than the red-green and red-blue gratings, but this was to an equivalent degree across the 2 groups.

Conclusions: Together, these findings indicate that greater chromaticity separation increases neural excitation, and that this effect is heightened in migraine, consistent with the theory that hyper-excitability of the visual system is a key signature of migraine.