Those who suffer from migraines have a hyperexcitable visual cortex, according to a study published in Neuroimage: Clinical. This is the first reported evidence establishing a link between migraine experiences and abnormalities in the visual cortex.
In previous studies, striped patterns have been shown to induce strong visual illusions and discomforts to migraineurs. To test this, researchers at the Center for Human Brain Health and School of Psychology at the University of Birmingham presented 60 volunteers, half of whom were a control group, with a striped grating pattern and asked them to rate whether the pattern was uncomfortable to look at. In addition, volunteers were asked to record if they experienced visual phenomena from viewing the image.
Specifically, the study compared “the visual evoked potentials (VEPs) elicited by striped patterns of specific spatial frequencies (0.5, 3, and 13 cycles per degree [cpd])” recorded by a group of migraineurs and nonmigraineurs. Of the 29 migraineurs included, 17 experienced migraine with aura and 12 had migraine without aura. All participants in the study were female. VEPs were also compared between hyperexcitable nonmigraineurs and nonhyperexcitable controls.
“We found that the migraineurs has a significantly increased N2 amplitude for stimuli with 13 cpd gratings but an attenuated late negativity (LN: 400-500 ms after the stimuli onset) for all the special frequencies,” researchers said.
In addition to documenting VEPs, participants underwent electroencephalogram tests so researchers could track and record brain wave patterns when visual stimuli were present, according to a press release.
Interestingly, when researchers considered results from nonmigraineurs who reported additional visual disturbances, “it was found that these participants also showed hyperexcitability in the response of their visual cortex,” authors said.
Ali Mazaheri, PhD, a lead author of the paper, stated in the release, “Our study provides evidence that there are likely specific anomalies present in the way the visual cortex of migraine sufferers processes information from the outside world. However, we suspect that is only part of the picture, since the same patterns of activity can also be seen in non-migraineurs who are sensitive to certain visual stimuli.”
The specific brain response patterns included larger responses in the visual cortex of migraineurs. Researchers will continue to monitor the group over time to see whether responses to visual stimuli changes when participants get close to experiencing a migraine. Researchers hope to track any other physiological changes that occur at this time, which could help forecast and ultimately prevent migraine onset.
Fong CY, Law WHC, Braithwaite JJ, et al. Differences in early and late pattern-onset visual-evoked potentials between self-reported migraineurs and controls [published online December 16, 2019]. Neuroimage Clin. doi: 10.1016/j.nicl.2019.102122.