The current trend in the diagnosis of epilepsy is
oriented towards high frequency activity that is used to
characterize the epileptogenic zone. Still, interictal spikes, i.e.
transient activity, remain a classical marker. A difficult
question is to separate these two classes of activity that overlap
in the time-frequency plane. We propose to use a temporal
basis set in order to describe and subtract spiking activity from
the traces, as a preprocessing step for further space-timefrequency
analysis. The set is based on singular value
decomposition. We select the first three temporal components,
construct a model of the spikes by projecting the data on the
new basis and obtain a spike-free signal by subtracting the
model from the original signal. We prove that despikifying
results in a better characterization of oscillatory activity,
promoting time and frequency separation. The resulting
spatio-temporal maps could help for a better characterization
of the oscillatory activity in electrophysiology of epilepsy.