Masked thresholds of auditory midbrain neurons in the frog Rana ridibunda.
Single-unit recordings from neurons in the torus semicircularis of Rana ridibunda were analyzed to determine the degree to which these neurons can detect acoustic stimuli superimposed on continuous, broad-band noise. In the first series of trials the stimuli were tone pulses 25 ms long, 5 dB above threshold, and at the characteristic frequency of the neuron. Most cells responded to the stimulus for signal-to-noise ratios of 25-35 dB (tone intensity minus spectral noise density); the lowest values were about 20 dB. The same signal-to-noise ratio was obtained with tones 20 dB above threshold. In the second series, conspecific mating calls at an intensity of 60 dB were tested. Here the signal-to-noise ratio (peak intensity of the call minus noise level) was usually 45-60 dB, in 5 of 27 cells it was 40 dB. Increasing the call intensity to 80 dB raised the SNR by an average of 6 dB. Noise-tolerant units more commonly gave synchronous responses to the pulse groups in the call, and are better tuned to its frequency range, than noise-sensitive units.
Joermann
G
G
Zoological Institute, University of Bonn, F.R.G.
D000819:Animal Communication; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology*; D005260:Female; D008297:Male; D008636:Mesencephalon / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D010470:Perceptual Masking / Q000502:physiology; D011895:Rana ridibunda / Q000502:physiology*; D011898:Ranidae / Q000502:physiology*