Potentiation instead of habituation characterizes visual evoked potentials in migraine patients between attacks

We have studied habituation of the pattern-reversal visual evoked potential (VEP) in healthy volunteers (n = 16) and in patients suffering from migraine without (n = 27) or with aura (n = 9). Five blocks of 50 responses at a stimulation rate of 3.1 Hz were sequentially averaged and analyzed separately for latencies, peak-to-peak amplitudes of N1-P1 and P1-N2, and the area under the N2 component Latencies of N1, P1, or N2 components were not significantly different between the sequential trial blocks, or between groups. Mean amplitudes of N1-P1 and P1-N2 in the first and subsequent blocks of SO responses were not statistically different among groups. In healthy subjects, there was a decrement of N1-P1 and P1-N2 amplitudes and N2 area on successive averagings. This habituation was maximal in the third and fourth blocks, but tended to disappear in the fifth block. In marked contrast to healthy subjects, migraine patients were characterized by a transient amplitude increment (i.e. potentiation) of VEP components which reached its maximum in the second to fourth blocks. Amplitude changes in sequential blocks were not dependent on attention and differed significantly between healthy subjects and migraineurs, but not between migraine with and without aura. Taken together with previous studies showing deficient habituation of contingent negative variation in migraine, these results indicate a dysfunction of central information processing which might have behavioral and pathogenic correlates.