The analysis of electrophysiological signal of scalp: EEG (electroencephalography), MEG (magnetoencephalography) and depth (intracerebral EEG) IEEG is a way to delimit epileptogenic zone (EZ). These epileptic signals present two different activities (oscillations and spikes) which can be overlapped in the time frequency plane. Automatic recognition of epileptic seizure occurrence needs several preprocessing steps. In this study, we evaluated two filtering techniques: the stationary wavelet transforms (SWT) and the Despikifying in order to extract pre ictal gamma oscillations (bio markers of seizure build up). Then, we used a temporal basis set of Jmail et al 2017 as a preprocessing step to evaluate the performance of both technique. Moreover, we used time-frequency and spatio-temporal mapping of simulated and real data for both techniques in order to predict seizure build up (in time and space). We concluded that SWT can detect the oscillations, but Despikyfying is more robust than SWT in reconstructing pure pre ictal gamma oscillations and hence in predicting seizure build up.