Cortical inhibition and habituation to evoked potentials: relevance for pathophysiology of migraine

Dipartimento di Neuroscienze Cliniche, University of Palermo, Via G. la Loggia, 1, 90129 Palermo, Italy.
The Journal of Headache and Pain (Impact Factor: 3.28). 03/2009; 10(2):77-84. DOI: 10.1007/s10194-008-0095-x
Source: PubMed

ABSTRACT Dysfunction of neuronal cortical excitability has been supposed to play an important role in etiopathogenesis of migraine. Neurophysiological techniques like evoked potentials (EP) and in the last years non-invasive brain stimulation techniques like transcranial magnetic stimulation (TMS) and transcranial direct current stimulation gave important contribution to understanding of such issue highlighting possible mechanisms of cortical dysfunctions in migraine. EP studies showed impaired habituation to repeated sensorial stimulation and this abnormality was confirmed across all sensorial modalities, making defective habituation a neurophysiological hallmark of the disease. TMS was employed to test more directly cortical excitability in visual cortex and then also in motor cortex. Contradictory results have been reported pointing towards hyperexcitability or on the contrary to reduced preactivation of sensory cortex in migraine. Other experimental evidence speaks in favour of impairment of inhibitory circuits and analogies have been proposed between migraine and conditions of sensory deafferentation in which down-regulation of GABA circuits is considered the more relevant pathophysiological mechanism. Whatever the mechanism involved, it has been found that repeated sessions of high-frequency rTMS trains that have been shown to up-regulate inhibitory circuits could persistently normalize habituation in migraine. This could give interesting insight into pathophysiology establishing a link between cortical inhibition and habituation and opening also new treatment strategies in migraine.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Objective High-frequency repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability. We investigated its effect on visual evoked potentials (VEPs) in migraine. Methods Thirty-two headache-free controls (CO), 25 interictal (MINT) and 7 preictal migraineurs (MPRE) remained after exclusions. VEPs to 8’ and 65’ checks were averaged in six blocks of 100 single responses. VEPs were recorded before, directly after and 25 minutes after 10 Hz rTMS. The study was blinded for diagnosis during recording and for diagnosis and block number during analysis. First block amplitudes and habituation (linear amplitude change over blocks) were analysed with repeated measures ANOVA. Results With 65’ checks, N70-P100 habituation was reduced in MINT compared to CO after rTMS (p = 0.013). With 8’ checks, habituation was reduced in MPRE compared to MINT and CO after rTMS (p < 0.016). No effects of rTMS on first block amplitudes were found. Conclusion RTMS reduced habituation only in migraineurs, indicating increased responsivity to rTMS. The magnocellular visual subsystem may be affected interictally, while the parvocellular system may only be affected preictally. Significance Migraineurs may have increased responsiveness to rTMS because of a cortical dysfunction that changes before a migraine attack.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 10/2014; · 3.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background and Objective People with migraine headache have altered interictal visual sensory-level processing in between headache attacks. Here we examined the extent to which these migraine abnormalities may extend into higher visual processing such as implicit evaluative analysis of visual images in between migraine events. Methods Specifically, we asked two groups of participants––migraineurs (N=29) and non-migraine controls (N=29)––to view a set of unfamiliar commercial logos in the context of a target identification task as the brain electrical responses to these objects were recorded via event-related potentials (ERPs). Following this task, participants individually identified those logos that they most liked or disliked. We applied a between-groups comparison of how ERP responses to logos varied as a function of hedonic evaluation. Results Our results suggest migraineurs have abnormal implicit evaluative processing of visual stimuli. Specifically, migraineurs lacked a bias for disliked logos found in control subjects, as measured via a late positive potential (LPP) ERP component. Conclusions These results suggest post-sensory consequences of migraine in between headache events, specifically abnormal cognitive evaluative processing with a lack of normal categorical hedonic evaluation.
    Brain Research 09/2014; · 2.83 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abnormal increased cortical responsivity to various types of stimuli plays a major role in migraine pathogenesis. Neurophysiological studies, however, have provided ambiguous findings of either hypo or hyper cortical excitability. This is why the term “dysexcitability” has been recently proposed to indicate a more general dysregulation of cortical excitability. The aims of this review are: 1) to provide existing knowledge and research advances in migraine pathophysiology; 2) to propose a unitary interpretation of apparently conflicting neurophysiological findings. Data of studies conducted in migraine through various evoked potentials techniques and non-invasive brain stimulation methods are reviewed, and in some cases reinterpreted according to more recent findings on migraine pathophysiology. In particular, we emphasize the concept that various methods of testing brain excitability may induce different degrees of cortical activation depending on the stimulus parameters used (e.g., intensity, frequency, and duration of stimulation), so shedding light on different pathophysiological aspects. Finally, we try to reconcile apparently conflicting neurophysiological data in the light of a unitary pathophysiological model, suggesting that a condition of interictal cortical hyperresponsivity, possibly due to a glutamatergic dysfunction, could represent the primum movens of migraine pathogenesis.
    Clinical Neurophysiology 09/2014; · 2.98 Impact Factor

Full-text (2 Sources)

Available from
Jun 10, 2014