Predicting the temporal responses of non-phase-locking bullfrog auditory units to complex acoustic waveforms

Axons from the basilar papilla of the American bullfrog (Raana catesbeiana) do not phase lock to stimuli within an octave of their best frequencies. N evertheless, they show consistent temporal patterns of instantaneous spike rate las reflected in peristimulus lime histograms) in response to repeated stimuli in that frequency range. We show that the second-order Wiener kern els for these axons, derived from the cross-correlation of continuous (non- repeating), broad-band noise stimulus with the spike train produced in resp onse to that stimulus, can predict with considerable precision the temporal pattern of instantaneous spike rate in response to a novel, complex acoust ic waveform (a repeated, 100-ms segment of noise, band-limited to cover the single octaves above and below best frequency). Furthermore, we show that most of this predictive power is retained when the second-order Wiener kern el is reduced to the highest-ranking pair of singular vectors derived from singular-value decomposition, that the retained pair of vectors corresponds to a single auditory filter followed by an envelope-detection process, and that the auditory Filler itself predicts the characteristic frequency (CF) of the axon and the shape of the frequency-threshold tuning curve in the v icinity of CF. (C) 1999 Elsevier Science B.V. All rights reserved.