Increased visual after-effects in migraine following pattern adaptation extend to simultaneous tilt illusion.
Much previous research into visual processing in migraine supports a model of abnormal cortical processing, in between the headache attacks, that is characterised by hyperexcitability, heightened responsiveness, a lack of habituation and/or a lack of intra-cortical inhibition. Shepherd (2001) reported two adaptation studies that challenged this view, one using the tilt after-effect, the second using the motion after-effect. Models of cortical function in migraine based on hyperexcitability and a lack of inhibition lead to specific predictions in an adaptation study: there should have been smaller after-effects in people with migraine than in people without. Both experiments, however, revealed larger after-effects in the migraine group than in the control group. Here, these results are extended to the simultaneous tilt illusion and an identical pattern of results was obtained: there were consistently larger effects in the migraine group than in the control group. The results from the three experiments are not consistent with a lack of inhibition in migraine. The results are discussed in terms of alternative models of cortical function, including a lack of excitation and reduced central energy reserves.
Shepherd
A J
AJ
School of Psychology, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK. a.shepherd@psychology.bbk.ac.uk
Palmer
J E
JE
Davis
G
G
D000221:Adaptation, Ocular / Q000502:physiology; D000328:Adult; D000360:Afterimage / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008881:Migraine Disorders / Q000503:physiopathology*; D009903:Optical Illusions / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010470:Perceptual Masking / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D014796:Visual Perception / Q000502:physiology*