Evidence for precortical, potentially retinal-based, abnormalities of the visual system in migraine

Abstract

Background In the retina, light is absorbed by the L-, M- and S-cone photoreceptors. Studies have shown that people with migraine perform worse than controls in experiments that assess sensitivity to S-cone stimuli. It is unclear whether these differences arise from dysfunction at cortical or precortical sites. Objective To localize the source of this abnormality, we took advantage of an experimental paradigm called transient tritanopia, in which observers exposed to a long wave-length adapting display experience a paradoxical reduction in sensitivity to short wave-length stimuli. There is strong evidence to suggest that this phenomenon is precortical/retinal in origin. Methods Participants with migraine and age-matched controls were tested to determine S-cone detection thresholds using a 4AFC procedure both before and after adaptation to (1) a long-wavelength (yellow) display, and (2) a control (grey) display. Results In both groups, adaptation to a long-wavelength display increased subsequent detection thresholds to S-cone stimuli. This loss of sensitivity was significantly greater in the migraine group. Loss of sensitivity following adaptation to a neutral display was minimal, and did not differ between groups. Conclusion Abnormalities in precortical sites may contribute to a loss of sensitivity in the detection of short-wavelength stimuli in migraine