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Kathryn Webster, J. Edwin Dickinson, Josephine Battista, Allison M. McKendrick, David R. Badcock; Increased Internal Noise Cannot Account for Motion Coherence Processing Deficits in Migraine. Journal of Vision 2011;11(11):434. doi: 10.1167/11.11.434.
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© ARVO (1962-2015); The Authors (2016-present)
Individuals with migraine, in-between migraine events, have previously exhibited higher coherence thresholds for global motion tasks than headache-free controls. The underlying mechanism is unclear. Studies have proposed that the visual cortex of migraineurs is hyperexcitable either through reduced inhibitory function or increased neuronal excitation either of which may result in increased internal (neuronal) noise. In this study, we examine whether increased internal noise can explain motion processing differences in migraine. The amount of internal noise was estimated using an N-Pass method which requires several runs, or passes, of identical stimuli to be completed by the participant with responses correlated across runs. Internal noise results in inconsistent responses to identical stimuli across different runs. Thirteen participants who experienced migraine (4 migraine with aura, 9 migraine without aura aged: 19–40) and 15 headache-free controls (aged: 24–34) participated in the current study. Participants completed three psychophysical tasks: 1) detecting coherence in a global-motion stimulus, 2) discriminating the spiral angle in a glass pattern and 3) discriminating the spiral angle in a global-motion stimulus. Inclusion of spiral tasks allowed a comparison of the precision of spiral angle coding in both form and motion stimuli. The method of constant stimuli was used to obtain thresholds estimates. There were two levels of external noise (0 and noise sufficient to double threshold) added to the stimuli in the spiral motion and form tasks. Consistent with previous research, migraineurs had significantly higher motion coherence thresholds than controls (t(25) = 2.36, p < .05) but there were no significant threshold differences between the same groups on the spiral global-motion and global-form tasks. Internal noise estimates were also equivalent across groups in all of the tasks, suggesting that differences in internal noise levels is not the mechanism driving higher motion coherence thresholds in migraine.
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