Insets are portions of both waveforms, presented simultaneously to the system at the direction of the interneuron's peak response. For the 23 Hz sine wave at this amplitude, a stochastic resonance peak was observed near an added input noise level of 25 times the r.m.s. 2 Results of presentations of broadband stimuli, covering the entire frequency and amplitude sensitivity ranges of the neurons, alone and with varying levels of broadband noise. Note that information rates always increased with increasing signal strength, as would be expected. Stochastic resonance peaks are seen for all three.
Error bars represent the s.e.m.
In these cases the neuron was encoding well with no noise, and additional input noise degraded the encoding rate. Each signal was presented either alone or simultaneously with an uncorrelated 5-400 Hz white noise background at one of 17 possible intensities. The interstimulus waiting period was 3 s. Total rate of information transmitted about the stimulus waveform by the elicited spike trains is plotted. Note that the information rate is directly related to the SNR through Shannon's formula 19 for gaussian distributions of signal and noise, such as those used here.