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Nitric oxide modulation of low-frequency oscillations in cortical vessels in FHM--a NIRS study.

ABSTRACT: The pathophysiological alterations in patients with familial hemiplegic migraine (FHM) are not yet fully known. The headache characteristics in patients with FHM mutations have been examined in a series of glyceryl trinitrate (GTN) provocation studies in FHM patients, but the cortical vascular response to GTN in FHM patients has never been investigated before.To investigate changes in spontaneous low-frequency oscillations (LFO) of cortical vessels in response to the nitric oxide donor GTN by near-infrared spectroscopy in FHM patients.Twenty-three FHM patients without known mutations and 9 healthy controls received a continuous intravenous infusion of GTN 0.5?µg/kg/minute over 20 minutes. Using near-infrared spectroscopy, we recorded oxygenated hemoglobin (oxyHb) LFO amplitude bilateral at the frontal cortex at baseline and 15 minutes and 40 minutes after start of the GTN infusion.GTN changed oxyHb LFO amplitude in FHM patients (P?=?.002), but not in healthy controls (P?=?.121). Only in FHM patients with coexisting common migraine types did GTN infusion induced changes in LFO amplitudes (P?

SUBMITTER: Schytz HW

PROVIDER: S-EPMC3730264 | biostudies-literature | 2012 Jul-Aug

REPOSITORIES: biostudies-literature

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Nitric oxide modulation of low-frequency oscillations in cortical vessels in FHM--a NIRS study.

Schytz Henrik W HW Hansen Jakob M JM Phillip Dorte D Selb Juliette J Boas David A DA Ashina Messoud M

Headache 20120221 7

<h4>Background</h4>The pathophysiological alterations in patients with familial hemiplegic migraine (FHM) are not yet fully known. The headache characteristics in patients with FHM mutations have been examined in a series of glyceryl trinitrate (GTN) provocation studies in FHM patients, but the cortical vascular response to GTN in FHM patients has never been investigated before.<h4>Objective</h4>To investigate changes in spontaneous low-frequency oscillations (LFO) of cortical vessels in respons ...[more]

PMID: 22352839

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Project description:Fine-scale temporal organization of cortical activity in the gamma range (?25-80Hz) may play a significant role in information processing, for example by neural grouping ('binding') and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes or slower oscillation phase codes, may resolve conflicting experimental observations on gamma phase coding. Our modeling results offer clear testable experimental predictions. We conclude that input-dependency of gamma frequencies could be essential rather than detrimental for meaningful gamma-mediated temporal organization of cortical activity.

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Nitric oxide modulation of low-frequency oscillations in cortical vessels in FHM--a NIRS study.

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Nitric oxide modulation of low-frequency oscillations in cortical vessels in FHM--a NIRS study.

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