Visual processing in migraineurs

Twelve migraine subjects with aura and 12 matched control subjects performed four computerized visual tasks. Because chronic electroencephalographic and regional cerebral blood flow abnormalities in posterior brain functions have been documented during interictal periods, migraine subjects were tested between migraine attacks. Two tasks, orientation detection and temporal order judgement, were devised to examine 'low-level' visual processes. The results were compared with results from two tasks, picture naming and word priming, that were devised to examine 'high-level' visual processes. Regarding the response time data across all four tasks, the migraine group was faster in the two low-level tasks. There were no differences in error rate in any of the four tasks. The migraineur's apparent response time advantage in the low-level tasks provides a psychophysical corroboration of their assumed oversensitivity to visual stimuli. The remaining two tasks, picture naming and word priming, which involve the use of previously stored information, do not distinguish migraineurs from matched control subjects. These results suggest that migraineurs are better in low-level visual processing, in that the signals to the primary visual cortex (Area V1) are processed more rapidly, but this hypersensitivity does not carry over to the subsequent processing stages (beyond V1 to superior parietal and inferior temporal cortices), as evidenced by the absence of a response time advantage in the two higher-level vision tasks.