Foci identification of spike discharges in the EEGs of sleeping El mice based on the electric field model and wavelet decomposition of multi monopolar derivations

We report on spike discharges in the EEGs of sleeping El mice, which are considered to be homologous to the state seen in human epileptic patients. The discrete wavelet transform (DWT) was used to decompose the EEGs derived from seven electrodes, with the primary spike frequency detected in the 15.6-7.8 Hz detail. The synchronicity of the spikes was evaluated in 98 samples. We succeeded in detecting the foci of the spikes by applying the electric field model, in which the surface potential was expressed as a function of distance between the focus and each electrode based on Gauss' theorem. The foci were obtained in 73 of 91 spikes so evaluated. In 69 of these 73 spikes, the calculated foci occurred within the brain, with none of the foci occurring at identical positions. The distribution occurred in relatively deeper brain regions, suggesting involvement of the paleocortex rather than the hippocampal system. The present study provides reasonable grounds for an explanation of the EEG using the electric field model supported by efficient foci detection of the spikes in a one-to-one correspondence. This paradigm will be applicable to all animal species including humans and will be helpful in the detection of the epileptic focus and in obtaining an insight into the mechanisms of spike genesis.