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| Research article summary (published 29 Apr 2003): |
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Gamma-band phase clustering and photosensitivity: is there an underlying mechanism common to photosensitive epilepsy and visual perception?
Full Abstract
Photosensitive epilepsy (PSE) is the most common form of human reflex epilepsy, appearing in up to 10% of epileptic children. It also offers a highly reproducible model to investigate whether changes in neuronal activity preceding the transition to an epileptic photoparoxysmal response (PPR) may be detected. We studied 10 patients with idiopathic PSE (eight female, mean age 26 years, range 9-51 years) using magnetoencephalography. In addition, we also studied the responses of five normal controls (mean age 24 years, age range 9-35 years) and three non-photosensitive epileptic patients (mean age 10 years, range 8-11 years). Spectral analysis of the MEG signals recorded during intermittent photic stimulation revealed relevant information in the phase spectrum. To quantify this effect, we introduced a second order response feature of the stimulus-triggered visual response preceding the
PPR:
the phase clustering index, which measures how close the phases of successive periods are grouped for each frequency component for all periods of the stimuli applied. We recorded a total of 86 PPRs, including several absence seizures, in nine of the 10 patients. We found that an enhancement of phase synchrony in the gamma-band (30-120 Hz), harmonically related to the frequency of stimulation, preceded the stimulation trials that evolved into PPRs, and differed significantly from that encountered in trials not followed by PPR or in control subjects. This novel finding leads us to postulate that a pathological deviation of normally occurring synchronization of gamma oscillations, underlying perceptional processes, mediates the epileptic transition in PSE.
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Author information
Author/s: Parra, J (J); Kalitzin, S N (SN); Iriarte, J (J); Blanes, W (W); Velis, D N (DN); Lopes da Silva, F H (FH);
Affiliation: Dutch Epilepsy Clinics Foundation, 'Meer en Bosch', Heemstede, The Netherlands. jparra@sein.nl
Journal and publication information
Publication Type: Journal Article; Research Support, Non-U.S. Gov't
Journal: Brain : a journal of neurology (Brain), published in England. (Language: eng)
Reference: 2003-May; vol 126 (issue Pt 5) : pp 1164-72
Dates: Created 2003/04/11; Completed 2003/07/18; Revised 2006/11/15;
PMID: 12690055, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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