  Two new surrogate methods, the Small Shuffle Surrogate (SSS) and the
Truncated Fourier Transform Surrogate (TFTS), have been proposed to study
whether there are some kind of dynamics in irregular fluctuations and if so
whether these dynamics are linear or not, even if this fluctuations are
modulated by long term trends. This situation is theoretically incompatible
with the assumption underlying previously proposed surrogate methods. We apply
the SSS and TFTS methods to microelectrode recording (MER) signals from
different brain areas, in order to acquire a deeper understanding of them.
Through our methodology we conclude that the irregular fluctuations in MER
signals possess some determinism.
