Electrostimulation of the paw is considered a basic paradigm to produce a reliable somatosensory response in animal fMRI. Yet, there is disagreement over the murine BOLD response: based on the anesthetic protocol either unilateral or bilateral patterns were reported. We hypothesize sympathetic activity as an origin of bilateral patterns, which is likely to be suppressed in protocols that employ α2-adrenoreceptor agonists. Utilizing finite impulse response (FIR) basis set modeling we present preliminary data that reveals "hidden" activity of brain structures which are known driving forces of sympathetic pathways. Our overall aim is to reveal the underlying mechanisms of this complex response to a simple paradigm and its implications for somatosensory mouse fMRI.