Get access

Visual contrast processing in migraine

Authors


  • 1

    The degrees of freedom are not integers because they have been adjusted for unequal variance using the Greenhouse–Geisser epsilon.

  • 2

    It is worth noting that nine of the original 53 migraine sufferers did not complete the 12 settings, but six of these did complete nine settings (3 VA, 2 NVA, 1 MwoA). Re-running the analysis on the first nine settings only but with these six and their matched controls included (n=50 in each group) did not alter the pattern of results. There was an overall effect of group (F(1, 47)=9.14, p=0.004), but no other significant effects (all F’s <1.8).

A.J. Shepherd, School of Psychology, Birkbeck College, University of London, Malet Street, London WC1E 7HX. Tel. 020 76316212, fax 020 76316312, e-mail: a.shepherd@psychology.bbk.ac.uk

Abstract

Some migraine sufferers report certain visual patterns can reliably trigger a migraine attack, such as high contrast striped patterns or flickering lights. Differences between people with and without migraine on tasks that involve these patterns have been attributed to abnormal cortical processing in migraine, although the locus and extent of the abnormality remains unclear, as is any relationship between impairment on various visual tasks. In this study 58 migraine sufferers and 61 control subjects participated in three visual tasks involving striped patterns. One assessed pattern sensitivity with high contrast patterns, the second detection thresholds for low contrast patterns and the third supra-threshold contrast scaling. With each measure, the performance of migraine sufferers as a group differed to the performance of non-migraine control subjects. There were no significant differences between the migraine subgroups when classified according to the presence or absence of aura. Cross-correlating the results from the three tasks, however, revealed consistent associations: impaired or extreme responses on one task were associated with impaired or extreme responses on the others. There were no overall effects due to migraine duration, the frequency of migraine attacks or the time since the last attack. These results are discussed in the context of visually induced migraine, proposed causes of abnormal cortical function in migraine and the prospects for developing clinically useful tests of visual function.

Ancillary