  We have studied the electronic structure of electron-doped cuprate
superconductors via measurements of high-field Shubnikov-de Haas oscillations
in thin films. In optimally doped Pr$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$ and
La$_{2-x}$Ce$_{x}$CuO$_{4\pm\delta}$, quantum oscillations indicate the
presence of a small Fermi surface, demonstrating that electronic reconstruction
is a general feature of the electron-doped cuprates, despite the location of
the superconducting dome at very different doping levels. Negative high-field
magnetoresistance is correlated with an anomalous low-temperature change in
scattering that modifies the amplitude of quantum oscillations. This behavior
is consistent with effects attributed to spin fluctuations.
