Abstract
Individuals with migraine generally experience photophobia and/or phonophobia during and between migraine attacks. Many different mechanisms have been postulated to explain these migraine phenomena including abnormal patterns of connectivity across the cortex. The results, however, remain contradictory and there is no clear consensus on the nature of the cortical abnormalities in migraine. Here, we uncover alterations in cortical patterns of coherence (connectivity) in interictal migraineurs during the presentation of visual and auditory stimuli and during rest. We used a high-density EEG system, with 128 customized electrode locations, to compare inter- and intra-hemispheric coherence in the interictal period from 17 individuals with migraine (12 female) and 18 age- and gender-matched healthy control subjects. During presentations of visual (vertical grating pattern) and auditory (modulated tone) stimulation which varied in temporal frequency (4 and 6 Hz), and during rest, participants performed a colour detection task at fixation. Analyses included characterizing the inter- and intra-hemisphere coherence between the scalp EEG channels over 2-s time intervals and over different frequency bands at different spatial distances and spatial clusters. Pearson’s correlation coefficients were estimated at zero-lag. Repeated measures analyses-of-variance revealed that, relative to controls, migraineurs exhibited significantly (i) faster colour detection performance, (ii) lower spatial coherence of alpha-band activity, for both inter- and intra-hemisphere connections, and (iii) the reduced coherence occurred predominantly in frontal clusters during both sensory conditions, regardless of the stimulation frequency, as well as during the resting-state. The abnormal patterns of EEG coherence in interictal migraineurs during visual and auditory stimuli, as well as at rest (eyes open), may be associated with the cortical hyper-responsivity that is characteristic of abnormal sensory processing in migraineurs.
Highlights
More than 38 million people in the United States suffer from migraine (Migraine Research Foundation (MRF), 2020), a neurovascular condition which manifests as episodes of headache, accompanied by other autonomic and neurological symptoms
We used a high-density electroencephalography (HD-EEG) system, with 128 customized electrode locations, to measure inter- and intra-hemispheric coherence from individuals with migraine (12 female) in the interictal period, and age- and gender-matched healthy control subjects, during visual and auditory stimulation which varied in temporal frequency (4 and 6Hz), and during rest
Response time Each participant’s reaction times (RT) were averaged over trials separately for stimulation frequency (4Hz and 6Hz) and modality, and these factors were subjected to an ANOVA with group as the between-subject variable
Summary
More than 38 million people in the United States suffer from migraine (Migraine Research Foundation (MRF), 2020), a neurovascular condition which manifests as episodes of headache, accompanied by other autonomic and neurological symptoms. Neurophysiological, morphometric, and functional imaging studies have focused on uncovering the pathogenesis, biomarkers, and effective treatments for this sometimes debilitating disorder. Notwithstanding this large scientific effort, there is still no consensus on the underlying mechanism/s that give rise to migraines. One candidate mechanism for migraine is altered functional cortical connectivity. Connectivity alterations have been identified in multiple cortical regions in the pre-ictal and ictal migraine phases (Chong et al, 2017), suggesting that abnormal functional connectivity is not a consequence of the migraine attack itself. Reviews of the functional connectivity findings from resting scans in migraine show inconsistencies across studies (Skorobogatykh et al, 2019). Some of the more consistent findings are abnormal connectivity between brain areas associated with pain, and between sensory areas (Hodkinson et al, 2016a), and strength of connectivity was related to headache severity (for a review, see Schwedt et al, 2015)
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