Page 159 - Migraine, the heart and the brain
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                                The post-ictal impact of a migraine attack on cognition
Moreover, recruiting patients for tests on cognitive functioning might bias the study towards patients with a higher education and, indeed, in our study the educational level was above average. Furthermore, migraineurs recognizing cognitive decline themselves (after an attack) might be more likely to participate in a study focusing on (post-attack) cognitive effects.
Finally, due to the rather high demands posed by our experimental protocol and the relatively selective recruiting procedure, only a limited number of patients could be tested. In addition, the requirement to match the members of the control group to the patients created a sample that was considerably more heterogeneous than the student samples that have been used to develop the tasks we employed. All this is likely to have increased the error variance and made our statistical tests relatively conservative. Therefore, the absence of statistically signi cant effects, such as with the numerically reversed global precedence effect in migraineurs or the interaction between group and session, should be interpreted with caution. In any case, the strength of the present study is the design with matched controls that were tested within the same time intervals and the exclusion of effects of the actual headache phase by delaying post-ictal testing until the  rst headache free day. Future studies on post-ictal cognitive functioning should probably exclude prophylaxis users and consider starting testing somewhat sooner after the (untreated) attack. While in previous studies on cognitive function in migraineurs, speci c differences were found between migraineurs with aura and migraineurs without aura, in future studies groups of both migraine with aura and without aura should be reasonable large to make comparisons between these groups.
In conclusion, no evidence for temporary changes in cognitive performance could
be found during the postictal phase (on average 17 hours after the end of the attack) 8 in migraineurs on attentional function, working memory, or perceptual organization
capabilities using this study design. However we found that the normal global
precedence was absent in migraineurs, speci cally in prophylaxis users a de cit that
is likely to impair the processing of the visual context and Gestalts.
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