Deep Brain Stimulation (DBS), besides an effective therapeutic tool, is a fascinating physiological window on human subcortical structures. In fact, local field potential (LFPs) recordings in patients provide an amount of physiological data on basal ganglia, especially in relation to their motor, cognitive and affective functions. In this study we aimed to assess a novel methodological approach for estimating the functional role of the basal ganglia. In particular, we focus here on decision making processes, by recording the scalp Electroencephalogram and Local Field Potentials oscillations from the Sub-Thalamic Nucleus in patients with Parkinsons disease who underwent neurosurgical procedures for Deep Brain Stimulation. Our results show that STN oscillations is modulated by the execution of gambling task. In particular, this modulation was different from that induced by the execution of a motor control task: whereas the motor task induced a desychronization in the low- and high-beta oscillation (10-20 Hz), gambling tasks synchronized beta activity in both sub-bands. We conclude that LFPs oscillations provide a direct window on STN activity during decision making. Since LFPs oscillations were differentially modulated by the gambling and motor task, the STN could be involved in a circuit encoding non-motor information during decision making processes.