Stochastic Resonance in an Overdamped Monostable System
  We show, the SR can appear in monostable overdamped systems driven by additive mix of periodical signal and white Gaussian noise. It can be observed as nonmonotonic dependence of SNR on the input noise intensity. In this sense it is similar to classical SR observed in overdamped bistable systems with potential barrier. 
N.V.Agudov, A.V.Krichigin