Neural vs mechanical tuning curves in the CF‐FM bats, Pteronotus parnellii rubiginosus

Abstract

In the mustache bat (P. p. r.), the CM recorded from the round window is sharply tuned at 61 kHz and shows a prominent transient response to a tone burst of about 61 kHz, i.e., it increases exponentially at the onset of the stimulus and decreases at its cessation. In terms of the time constant (1.1 msec) and the resonance frequency (61.1 ± 0.43 kHz) of this transient response, the Q value of this system is 205 ± 56. Peripheral neurons sensitive to 61 kHz have a very sharp excitatory area (or tuning curve). The Q value of a tuning curve drastically increases with the rise in best frequency up to 61 kHz and decreases beyond 61 kHz. The average Q value of single neurons with best frequencies between 60.76 and 61.75 kHz is 209 ± 91. If the assumption that the CM is directly related to the mechanical motion of the basilar membrane is correct, the very sharp tuning curves of single neurons at about 61 kHz could be simply due to the mechanical tuning of the basilar membrane. [Work supported by NSF.]