Fig. 9.

Reconstruction of the calling song of a “one-hindlegged” grasshopper. A, AM signal. This signal has not yet been thresholded and is displayed on a decibel scale. B, Reconstruction of the signal, thresholded at 55 dB, for different stimulus intensities (peaks at 58, 64, 70, and 76 dB). Four spike trains from two cells with thresholds of 55 dB were pooled. At sound-pressure levels just exceeding the firing threshold, only the onset of each syllable is encoded in the spike train. With increasing sound intensity, more and more details of the song appear in the reconstruction, until at 21 dB above threshold even the short gaps of 2 msec length are almost perfectly preserved. Note that in the last reconstruction, the maximum amplitude of each reconstructed syllable remains approximately the same throughout the entire song. This demonstrates that adaptation effects balance the rising overall intensity of the song. Downstream processing stages therefore receive a fairly invariant representation of each syllable onset.