A new form of stochastic resonance (SR) that occurs in multilevel threshold signal detectors is reported. In contrast to classical SR, which extends the dynamic range of threshold detectors to subthreshold signal levels, this new form of SR extends the dynamic range to suprathreshold signal strengths. The effect is most dominant, and can outperform networks based on standard engineering design, when all thresholds adapt to the dc level of the signal. This has an interesting analogy to dc adaptation in neurons. The possible connection between these two effects is discussed.

• Received 18 June 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.2310