UBC Theses and Dissertations
Attentional and cognitive consequences of migraine visual cortical hyperexcitability Mickleborough, Marla Joy Sanderson
People with migraine have hyperexcitable visual cortical response to normal visual inputs between attacks. Given that our attentional and perceptual processing can be influenced by our sensory experience, we might expect migraine visual cortical hyperexcitability to have a forward cascade of effects on cognitive processing. With this in mind, this dissertation explored the functional consequences of migraine hyperexcitable visual cortices on attentional and cognitive processing between headache attacks. To begin with, given that top-down attentional control signals can affect excitability of sensory response in visual cortex, Chapter 2 assessed if this normal modulation is affected in migraineurs. Using a probabilistic spatial orienting task while measuring ERPs to attended vs. unattended foveal and parafoveal stimuli, Chapter 2 revealed that migraineurs manifest heightened sensory responses of to-be-ignored visual stimuli. Next, Chapter 3 examined the behavioral impact of hyperexcitability of migraine visual cortex in terms of its effect on bottom-up attentional processing, in this case reflexive attentional orienting. Using three behavioral spatial attention paradigms, this chapter provided evidence of heightened reflexive visual-spatial orienting specific to sudden-onset peripheral events. Lastly, Chapter 4 assessed post-spatial-selection consequences of visual cortical hyperexcitability in migraineurs. Participants viewed unfamiliar commercial logos in the context of a target identification task while brain responses were recorded via ERPs. Following this task, participants individually identified those logos that they most liked or disliked. The results of this chapter suggested that migraineurs were not only evaluating environmental stimuli more than controls over time, but also not adequately hedonically categorizing it for quick allocation of attention. Collectively, the research presented in this dissertation suggests that migraineurs have anomalies specifically pointing to increased allocation of attention to extraneous environmental stimuli. The final concluding chapter briefly recaps each research chapter and then critically examines the impact of these findings in the context of four outstanding questions exposed by this research. Specifically, are top-down attentional control signals in migraineurs intact? How might anomalies found in this dissertation be a result of or independent from known sensory cortical abnormalities? How do the findings fit with the migraineur experience? Finally, what are the real-world clinical implications for migraineurs?
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