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.
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
Inna
I
Midzyanovskaya
Vasily
V
Strelkov
Clementina van
Cv
Rijn
Boguslava
B
Budziszewska
Egidius
E
van Luijtelaar
Galina
G
Kuznetsova
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