Vocal Responses of “CF-FM Bats” to Electric and Acoustic Stimuli

Abstract

The experiments were performed for the exploration of coupling between the auditory and vocalization systems of awake bats, Pteronotus parnellii and P. suaprensis. The electric stimulation of the midbrain elicited the emission of sounds identical to species-specific orientation sounds consisting of CF and FM components. When acoustic stimuli were delivered with the electric stimuli, the electrically evoked sounds increased in amplitude and number. In P. parnellii these vocal responses were selectively sensitive to 62–63 kHz sounds, comparable to the CF component in its orientation sound, and also to downward-sweeping FM sounds comparable to the FM components in the orientation sound. In P. suaprensis, the threshold of the vocal response was high for pure tones and upward-sweeping FM sounds, but low for downward-sweeping FM sounds. The vocalization system was thus coupled with the auditory system by particular types of auditory neurons. These data indicate that the responses to acoustic stimuli were related not only to these power spectra, but also to properties of single auditory neurons and information-bearing elements in an emitted signal.