  Resistive switching is one of the key phenomena for applications such as
nonvolatile memories or neuromorphic computing. V3O5, a compound of the
vanadium oxide Magn\'eli series, is one of the rare materials to exhibit an
insulator-metal transition (IMT) above room temperature (Tc ~ 415 K). Here we
demonstrate both static dc resistive switching (RS) and fast oscillatory
spiking regimes in V3O5 devices at room temperature (120 K below the phase
transition temperature) by applying an electric field. We use operando optical
imaging to track a reflectivity change during the RS and find that a
percolating high temperature metallic phase filament is formed. This
demonstrates that the electrically induced RS triggers the phase transition.
Furthermore, we optically capture the spiking oscillations that we link to the
negative differential resistance regime and find the filament forms and
dissolves via a periodic spatio-temporal instability that we describe by
numerical simulations.
