Spectr dynamic of electrical activity of guinea pig brain structures during experimental status epilepticus.
Bondar А.Т.1, Shubina L.V.2
1Federal State Institution of Science Institute of Cell Biophysics, 2Federal State Institution of Science Institute of Theoretical and Experimental Biophysics, Pushchino, Moscow Region, Russia; firstname.lastname@example.org
Changes of the local field potentials (LFP) were studied during the interictal and recurrent ictal phases of the kainic acid-induced (i.c.v., 0.4µg) status epilepticus (SE) in guinea pigs. Dynamic spectral analysis was applied to explore the dynamics of rhythmic components of the spectrum in the process of SE development. Background electrical activity of the all studied structures was characterized by presence of well defined peak at 1,3-1,8 Hz and also sometimes at twice frequency (2,6-3,6 Hz) in the frequency spectra. 1-2 minutes after kinic acid injection sustained limbic seizures (status epilepticus) lasting for several hours were appeared. SE was accompanied by significant changes of the LFP spectra and first of all by appearance of the paroxysms. Character of the changes in the spectra of interictal and recurrent ictal phases varied considerably. Thus during the development of the SE components reflecting serial cascade of dominant background rhythm frequency doubling appeared in the spectra of the interictal phases of SE. In this case the dominance shifted to the double background frequency. Paroxysmal activity developed in the three different scenarios in spite of the fact that all of them had similar episodes with typical patterns. The frequency spectra of these patterns represented a Fourier series with the first harmonic correspon-ding to one of the members of the cascade of doublings in the interictal spectrum. The analysis showed that the emergence of multiple harmonics did not reflect the appearance of new rhythmic processes in the system but rather it was the change of the signal shape. The signal started to take the “peak-wave” shape and revealed one of the frequencies inherent in the interictal spectra.
Thus the formation of spectral components during the interictal and recurrent ictal phases of the kainic acid-induced SE is the result of the different processes. In the interictal phases the formation of the new rhythmic processes in the system (the cascade of doubling of frequency) took place whereas during the ictal phases
oscillations changed their shape to the “peak-wave” activity. It is supposed that the common mechanism can be the basis of these processes namely the cascade of the recurrent multiplications of the basic rhythm dominating in the background activity before the development of the SE.
This work was supported by Russian Humanitarian science Foundation, grant № 12-06-00198 and the grants of the President of the Russian Federation “The Scientific School” №850.2012.4 and Russian Foundation for Basic Research №12-04-00776-а.