**2. Mathematical model of the SCR process: A series of integrations with three feedback loops**

System identification approach enables to look into the process of the SCR in a neurophysiologically meaningful way. Through this method we approximate the whole arousal process (from the initial central neural event to the SCR output) as a series of integrators, with the integration constant of 100 ms, which corresponds to the temporal scale of brain neural integrations (Varela et al., 2001; Koch et al., 1996; Koch, 2005). Knowing the dynamic model of the SCR process enables further examination of the neurochemical meaning of the system parameters and eventually association of the identified regulatory signals with the activity of specific neurotransmitter systems.
