Lack of habituation of visual evoked potentials in migraine and healthy subjects: Correlated cognitive behavioral aspects

Dear Editor,

We read Lisicki’s interesting paper, recently published in Cephalalgia, which focused on the influence of a positive familial history of migraine on visual evoked potential (VEP) amplitude and habituation (1). The authors showed significant reduced habituation in migraineurs and their healthy first-degree relatives, concluding that it may be a genetically determined endophenotypic trait associating both migraine and migraine susceptibility.

Lisicki and co-authors correctly cited our recent report (2); however, we would like to add the following remarks concerning our findings:

We demonstrated an association between VEP habituation deficit and healthy subjects in a subset among them, characterized by higher scores in analytic information processing style (2). This cognitive behavior was linked to migraine in a large sample size of migraine patients by our previous study (3). On the contrary, we did not find an association between healthy subjects, characterized by the opposed cognitive style i.e. “global”, and migraine or lack of habituation (2,3).

Healthy analytical individuals recruited in our investigation showed significant VEP habituation deficit and similarly to migraineurs also reduced N1-P1 first block amplitude compared to the global healthy group (2). It must be noted that all involved subjects had never suffered from migraine and did not have migraineurs among their first-degree relatives.

According to Sternberg, analytic style of information processing can be present in closest relatives independently of genetic inheritance since the children’s style may be influenced by the parents’ style during development (3). Therefore, considering the above stressed evidence, it can be supposed that deficit of habituation associated with analytic style (2) might also be present among first-degree relatives regardless of genetic determinants. However, it remains to be clarified whether the source of cognitive style is genetically or epigenetically determined, or if it develops in response to early experiences or to attachment styles (2).

Keeping in mind the main features of an analytic information processing style (dealing with details, continuous arousal state, increased brain energy demand), the demonstrated link with impaired habituation (2) and the fact that in migraineurs habituation normalizes ictally, we put forward the idea of migraine attack as a compensatory mechanism against sensory overload linked to this cognitive behavioral factor (2,3).

In this scenario, the implication of serotonin and ovarian steroid estrogen in modulating learning and memory processes might account for sexual dimorphism in migraine and its menstrual cycle related fluctuation.

As has been demonstrated, cognitive style can be modified and taught. It would thus be interesting to investigate if a modification of analytic mode of information processing could affect the associated reduced habituation, therefore reverting this neurophysiological behavior and possibly accounting for migraine improvement (2).

In conclusion, as Montagna previously stressed, epigenetic factors and attachment styles may be important in the pathophysiology of primary headache (3). In addition we believe that analytic cognitive style, being linked to impaired habituation (2), is a variable to be considered in studying the complicated migraine puzzle and its neurophysiological correlates.