Increase in 20–50Hz (gamma frequencies) power spectrum and synchronization after chronic vagal nerve stimulation

Abstract

Objective: Though vagus nerve stimulation (VNS) is an important option in pharmacoresistant epilepsy, its mechanism of action remains unclear. The observation that VNS desynchronised the EEG activity in animals suggested that this mechanism could be involved in VNS antiepileptic effects in humans. Indeed VNS decreases spiking bursts, whereas its effects on the EEG background remain uncertain. The objective of the present study is to investigate how VNS affects local and inter regional syncronization in different frequencies in pharmacoresistent partial epilepsy. Methods: Digital recordings acquired in 11 epileptic subjects 1 year and 1 week before VNS surgery were compared with that obtained 1 month and 1 year after VNS activation. Power spectrum and synchronization were then analyzed and compared with an epileptic group of 10 patients treated with AEDs only and with 9 non-epileptic patients. Results: VNS decreases the synchronization of theta frequencies (P!0.01), whereas it increases gamma power spectrum and synchronization (!0.001 and 0.01, respectively). Conclusions: The reduction of theta frequencies and the increase in power spectrum and synchronization of gamma bands can be related to VNS anticonvulsant mechanism. In addition, gamma modulation could also play a seizure-independent role in improving attentional performances. Significance: These results suggest that some antiepileptic mechanisms affected by VNS can be modulated by or be the reflection of EEG changes. q

Neocortical pathological high-frequency oscillations are associated with frequency-dependent alterations in functional network topology

“…Theta band connectivity has also been proposed as an early diagnostic test for epilepsy (Douw et al 2010a), and pathologically elevated theta connectivity has related to greater seizure frequency (Douw et al 2010b). Finally, a treatment of epilepsy, vagus nerve stimulation, has previously been shown to increase and decrease gamma and theta band connectivity, respectively, underscoring the potential relevance of our findings for seizure control (Marrosu et al 2005).…”

Recording of bioelectrical activity changes in sheep cerebral cortex

“…Therefore, it may be unambiguously stated that occurring potentials correspond to the commonly accepted standards. In the case of humans, presently ac cepted standardization (Salansky et al 1998, Aurlien et al 1999, Finnerup et al 1999, Nishida 1999, Razoumnikova 2003, Rowan et al 2004, Marrosu et al 2005, LeVan et al 2006 allows to determine the neurophysiological state of a patient. The research is so advanced that, as it is suggested by Velis (2005), it is possible to determine the predispositions for a job performance on the basis of elec troencephalogram.…”

Vagus Nerve Stimulation in Refractory Epilepsy: State of the Art

“…CSF aspartate level, an excitatory neurotransmitter, has also been shown to decrease significantly in chronic VNS. On an electrical point of view, EEG studies have proven cortical synchronization or desynchronization depending on stimulation frequency and intensity, explaining the importance of rigorous stimulation parameters in VNS (Marrosu 2005).…”