title: Abnormal inhibition-excitation imbalance in migraine.
abstract: BACKGROUND
  People with migraine show increased surround suppression of perceived contrast, a perceptual analogue of centre-surround antagonistic interactions in visual cortex. A proposed mechanism is that cortical 'hyperexcitability' or 'hyperresponsivity', a prominent theory in the migraine literature, drives abnormal excitatory-inhibitory balance to give increased local inhibition. The purpose of this cross-sectional study was to determine whether cortical hyperresponsivity and excitatory-inhibitory imbalance manifests in the visual cortical response of migraine sufferers.
  
  
  METHODS
  Interictal steady-state visual evoked potentials (VEPs) in response to 0 to 97% contrast were recorded in 30 migraine participants (15 without aura, 15 with aura) and 21 non-headache controls. Monotonicity indices were calculated to determine response saturation or supersaturation. Contrast gain was modelled with a modified saturating hyperbolic function to allow for variation in excitation and inhibition.
  
  
  RESULTS
  A greater proportion of migraine participants (43%) than controls (14%) exhibited significant VEP supersaturation at high contrast, based on monotonicity index (chi-square, p = 0.028). Supersaturation was also evident by the trend for greater suppressive exponent values in migraine compared to control individuals (Mann-Whitney rank sum, p = 0.075).
  
  
  CONCLUSIONS
  Supersaturation in migraine is consistent with excess excitation (hyperresponsivity) driving increased network inhibition and provides support for excitatory-inhibitory imbalance as a pathophysiological disturbance in migraine.
authors: Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia bnguyen@unimelb.edu.au.
authors: Bao N
authors: BN
authors: Nguyen
authors: Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia.
authors: Allison M
authors: AM
authors: McKendrick
authors: Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia.
authors: Algis J
authors: AJ
authors: Vingrys
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005074:Evoked Potentials, Visual / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D053444:Inhibitory Postsynaptic Potentials / Q000502:physiology; D008297:Male; D020325:Migraine with Aura / Q000175:diagnosis / Q000503:physiopathology*; D020326:Migraine without Aura / Q000175:diagnosis / Q000503:physiopathology*; D014793:Visual Cortex / Q000502:physiology*; D055815:Young Adult
keywords: Inhibition; electrophysiology; excitation; migraine; supersaturation; vision