Measuring clusters of spontaneous spike-wave discharges in absence epileptic rats.
Spike-wave discharges (SWDs) characterizing absence epilepsy appear in closely packed aggregated sequences, which gave rise to the name "pyknolepsy" for this disease. In WAG/Rij rats, genetically prone to absence epilepsy, spontaneous SWDs seem to occur in clusters as well. Here, we aimed to quantify the seizures' clusters. SWDs sequences were extracted from long-term (complete estrous cycle) EEG recordings of adult female WAG/Rij rats. Spectral characteristics and half-decay time of autocorrelation functions (AC-tau) were calculated for time series of i(SWD) (proportion of time occupied by spike-wave activity), measured for subsequent periods. The clusters were characterized by means of AC-tau calculated for time series of i(SWD). The absence seizures were indeed clustered in a minute range. The clustering had a non-periodical character, since no significant and consistent periodicity was found in the minute range. AC-tau correlated positively with propensity of SWDs: i.e. the aggravation of absence epilepsy led to longer sequences of paroxysms and thus to a less random distribution. AC-tau was not sensitive to various phases of the estrous cycle, but was larger in the dark than in the light periods. We suggest that AC-tau can be used to quantify aggregation of epileptic events in the search for physiological basis of its temporal clustering.
Midzyanovskaya
Inna
I
Laboratory of Physiology of Temporal Relations, Institute of Higher Nervous Activity and Neurophysiology of Russian Academy of Sciences. Butlerova St. 5a, Moscow GSP-7, Russian Federation. miinn@yandex.ru
Strelkov
Vasily
V
Rijn
Clementina van
Cv
Budziszewska
Boguslava
B
van Luijtelaar
Egidius
E
Kuznetsova
Galina
G
D000465:Algorithms; D000818:Animals; D016000:Cluster Analysis; D003624:Darkness; D004569:Electroencephalography / Q000379:methods* / Q000706:statistics & numerical data; D004832:Epilepsy, Absence / Q000235:genetics / Q000503:physiopathology*; D030762:Estrous Cycle / Q000502:physiology; D005260:Female; D008027:Light; D051381:Rats; D011919:Rats, Inbred Strains