Top-down control of visual cortex in migraine populations

The pathophysiology of migraine includes a heightened excitability of visual cortex that persists between headache events and that has been linked to impaired inhibitory intracortical processes. Here we examined the hypothesis that this cortical pathophysiology would affect the top-down attentional control of visual cortex. We asked two groups of participants-migraineurs (N = 29) and non-migraine controls (N = 29) to perform a probabilistic spatial orienting task as we measured visual sensory cortical responses via event-related potentials (ERPs). Data were then analyzed as a function of whether the ERP-eliciting stimulus was in the fovea vs. parafovea, and whether the stimulus' location was attended or unattended. In this regard, we found two key between-groups differences in the effect of attention on sensory-evoked visual-cortical activity. First, relative to controls, migraineurs showed a larger attention effect in the visual N1 ERP component for events at the fovea. Second, unlike controls, migraineurs showed no early-phase attention effect in the P1 ERP component for events in the parafovea. Despite these altered ERP responses in migraineurs, however, corresponding behavioral data indicated that they also had heightened response performance. Taken together, our results support the hypothesis that migraineurs have an altered top-down attentional control of visual cortex, with the data suggesting that the effect may be tied to a reduced ability to suppress sensory-evoked activity for unattended events in the visual periphery. (C) 2011 Elsevier Ltd. All rights reserved.