In their hallmark work McMillan and  Rowell (W.L. McMillan 1965)  studied the lead phonon spectrum, and unequivocally established them as the paring mediator in the conventional BCS (J. Bardeen 1957) superconductors. To date, despite enormous efforts, there is no consensus on the origin of the superconducting glue in the high temperature cuprates superconductors.  In our work we report a detailed spectroscopic study of the electron doped cuprate superconductor Pr_2-xCe_xCuO_4-δ (PCCO) using point contact junctions. We measured three different doping levels including the under and over doped regimes of the phase diagram. From our conductance measurements we are able to identify bosonic resonances for each of the doping levels. These excitations disappear above the critical temperature, and above the critical magnetic field. We find that the energy of the bosonic excitations decrease when increasing the the doping level. This leads us to the conclusion that the bosonic mediator for these cuprates is spin excitation.