Peripheral Auditory Neurons Research Articles

Peripheral specialization for analysis of Doppler-shifted echoes in the auditory system of the “CM-FM” bat, Pteronotus parnellii. II. Properties of peripheral auditory neurons

The inner ear of the mustache bat (Pteronotus parnellii) is sharply tuned to sounds at 61–62 kHz and shows a prominent nonlinearity for 60–61-kHz sounds. Because of this nonlinearity, cochlear microphonic responses show prominent transients at the onset and cessation of 60–61-kHz sounds and the N1 response appears at the onset and the cessation of these stimuli. The N1-on is tuned at 63–64 kHz and is different from the best frequency of the CM-on, 61–62 kHz. This difference is due to the properties of a sharply tuned resonator and N1. The N1-off is tuned at 60–61 kHz as the CM-off is. Single peripheral neurons sensitive to 61–62-kHz sounds have an unusually sharp tuning curve. The low-frequency and high-frequency slopes are 2500–3000 and 2500–4200 dB/octave, respectively. The Q−10-dB value is as high as 300. Neurons with a best frequency between 58 and 64 kHz show not only tonic on-responses but also off-responses which are tuned at 60–61 kHz and are apparently related to the CM-off. These off-responses are not rebounds from neural inhibition. No neurons were found which showed only off-responses preceded by suppression or inhibition of background activity. [Supported by NSF Grant GB-40018.]