FIGURE 11 | Determination of the origin of the three types of oscillatory activity using a renewal density analysis (RDA). (A,B) RAW FFT (gray lines) and RDA FFT (black lines) of neuronal background activity of two SC cells presented in Figure 2 , a small decrease of peak amplitude in dominant frequencies in both cases (23 and 70Hz, respectively) does not suggest the extrinsic source of oscillations. (C,D) Example of ACH for raw data of neuron presenting oscillations classified as stimulus-phase-independent, and power spectra for raw data (gray line) and surrogate spike train containing shuffled inter-spike intervals (black line). The difference in power spectra of raw and surrogate data indicates the extrinsic source of oscillation in this neuron activity due to prominent peak disappearance (57Hz). (E,F) Example of ACH for the neuron, which oscillatory activity was classified as phase-locked, and the related power spectra for the raw and surrogate spike trains. Complete peak disappearance in dominant frequency (20Hz) in RDA FFT indicates an extrinsic source of the stimulus-phase-locked oscillations.