Epilepsy is a well-known affliction characterized by recurrent, unprovoked seizures affecting 1-2% of the population. Other than the actual seizure and the risks involved in it, the sudden and unpredictable nature of the seizure is one of the most disabling aspects of epilepsy. As such, finding a method capable of predicting epileptic seizures would open new therapeutic possibilities. When using electrocorticography for capturing brain activity of epileptic patients, usually, it is the clear increase in the brain activity that is recorded during the seizure. The data is usually used in order to find the probable focus of the seizure. Using the same data, we have applied a method that was used for another disorder (Ataxia Telangiectasia), for obtaining quantitative information about changes in the network correlation, rather than network activity. We show that this provides insight for the epileptic brain behavior, demonstrating that other locations of the brain are involved in the seizure other than the focus, and that there mig. Localization of the epileptogenic zone, defined as the volume of brain tissue necessary and sufficient for the generation of seizures, has traditionally depended on scalp EEG recordings which oÑ–en do not provide sufficient accuracy and resolution. In these cases, further evaluations rely on invasive brain recordings, using arrays of ECoG electrodes placed directly on the surface of the brain, and/or recordings from depth electrodes inserted deeper into the brain to regions such as the hippocampus or the medial temporal lobe. Нe ECoG systems used record up to 128 channels. Нe channels were divided into 4 x 8 or 8 x 8 arrays, and strips of up to 8 electrodes. Нe arrays and strips were placed based upon previous examination of the patients’ brain by PET and MRI. Нe signals were initially recorded at 400 Hz, digitized to 112 Hz and low passed filtered at 40 Hz. Seizure data included at least two episodes per patient, and data between seizures ranged from 30 to 160 min per patient. Typically, all ECoG channels are referenced to a common reference electrode.While being a small sample of patients, this work has been done to examine the application of measuring network variation for epilepsy. Doing so, we have noticed that this representation of the ECoG signals can indeed reveal important aspects of the brain activity in both space and time. Correlation variation provides a stronger signal than activity for diوٴering between normal activity and seizures. We have noticed a change in correlation variation occurring some time before the epileptic seizure takes place, during the “pre-seizure” period, but it is not clear if this will be valid for all epilepsy patients. Нe aura sensation which is experienced by many patients might suggest that the preseizure period is common. We have demonstrated that it is sufficient to measure the correlation of few channels in order to depict the correlation variation early signals. Нese observations suggest that future treatment of epilepsy which does not rely upon cortical tissue removal but rather upon stimulation [40-42] can depict the epileptic seizure with very few electrodes by monitoring their correlation. Doing so, we might be able to predict the seizure and eliminate it before it starts. Нe oوٴ-diagonal “hotspots”, the high correlation-variation areas in the brain, are also relevant for potential treatment: in cases that the seizure foci cannot be removed, because it is located in a critical brain area, removing the oوٴ-diagonal “hotspots” might allow preventing the seizure from advancing. If stimulation is to be used, stimulating these areas when a seizure is detected (or predicted) will cause them to be exhausted when the seizure wave reaches them, causing the wave to decay. Нe authors would like to thank Prof. O. Sagher from the University of Michigan, for sharing his ECoG recordings with us. Нis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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