Fig 2. Noise enhances action potential firing in a DRG neuron.

(A) Step stimuli (left) or noise alone (middle) fail to elicit action potentials (superimposed responses, top traces), while the step + noise (right) consistently elicits spikes in all 5 trials in a block. Step duration, 30 ms. (B) In the same neuron, the number of spikes changes if noise amplitude is reduced (left) or increased (right). (C) The normalized power norm C₁ in the same neuron; each square represents the value obtained in a single block. The clear maximum at intermediate noise variance demonstrates the occurrence of stochastic resonance. Inset: The decay phase of action potentials is monotonic in this neuron. (D) In a neuron showing a clear hump in the decay phase of the spike (inset), the plot of C₁ vs. noise variance is similar to that presented for the fast neuron in (C)