Spike rate versus AMPA input current (0 dB set = 5 pA, or an average of about an EPSC every 16 msec).

<p>Comparison is made to linear filter performance for four model variations: large light green dots = low threshold (5 pA) medium spontaneous rate (10 Hz) fiber with a 40 dB dynamic range, red dots = same, but with simulated LOCS feedback that turns off H current, small dark green dots = low threshold model including 300 microvolts RMS of Johnson voltage noise (spontaneous rate increased to ∼20 Hz). Blue dots = high threshold (38 pA) low spontaneous rate (0 Hz) fiber with 26 dB dynamic range. Central line corresponds to spike rate going like the first power of input current, while in the top and bottom lines spike rate goes like 1.1 or 0.9 power, respectively. Fast negative feedback is able to linearize ANF output and to greatly increase its dynamic range. Simulated LOCS feedback that is able to decrease H current is able to increase the number of spikes per dB in the upper intensity range of the low threshold fiber from about 7 to 12, which would increase the information content of auditory spike trains in noisy environments.