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Neuroscience Journal
Volume 2014, Article ID 370764, 6 pages
http://dx.doi.org/10.1155/2014/370764
Research Article

Age-Dependent Increase of Absence Seizures and Intrinsic Frequency Dynamics of Sleep Spindles in Rats

1Institute of the Higher Nervous Activity and Neurophysiology of Russian Academy of Sciences, Butlerova Street 5A, Moscow 117485, Russia
2Research and Educational Center “Nonlinear Dynamics of Complex Systems”, Saratov State Technical University, Saratov, Polytechnicheskaya Street 77, Saratov 410054, Russia
3Faculty of Nonlinear Processes, Saratov State University, Saratov, Astrakhanskaya Street 83, Saratov 410012, Russia
4Saratov State University, Astrakhanskaya Street 83, Saratov 410012, Russia

Received 28 April 2014; Revised 1 June 2014; Accepted 2 June 2014; Published 23 June 2014

Academic Editor: Pasquale Striano

Copyright © 2014 Evgenia Sitnikova et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The risk of neurological diseases increases with age. In WAG/Rij rat model of absence epilepsy, the incidence of epileptic spike-wave discharges is known to be elevated with age. Considering close relationship between epileptic spike-wave discharges and physiologic sleep spindles, it was assumed that age-dependent increase of epileptic activity may affect time-frequency characteristics of sleep spindles. In order to examine this hypothesis, electroencephalograms (EEG) were recorded in WAG/Rij rats successively at the ages 5, 7, and 9 months. Spike-wave discharges and sleep spindles were detected in frontal EEG channel. Sleep spindles were identified automatically using wavelet-based algorithm. Instantaneous (localized in time) frequency of sleep spindles was determined using continuous wavelet transform of EEG signal, and intraspindle frequency dynamics were further examined. It was found that in 5-months-old rats epileptic activity has not fully developed (preclinical stage) and sleep spindles demonstrated an increase of instantaneous frequency from beginning to the end. At the age of 7 and 9 months, when animals developed matured and longer epileptic discharges (symptomatic stage), their sleep spindles did not display changes of intrinsic frequency. The present data suggest that age-dependent increase of epileptic activity in WAG/Rij rats affects intrinsic dynamics of sleep spindle frequency.