We used spatially-resolved NEXAFS (near-edge x-ray absorption fine structure) spectroscopy coupled with microscopy to characterize the electronic, structural and chemical properties of bipolar resistive switching devices. Metal/TiO2/metal devices were electroformed with both bias polarities and then physically opened to study the resulting material changes within the device. Soft x-ray absorption techniques allowed isolated study of the different materials present in the device with 100 nm spatial resolution. The resulting morphology and structural changes reveal a picture of localized polarity-independent heating occurring within these devices initiated by and subsequently accelerating polarity-dependent electrochemical reduction/oxidation processes.