Neurophysiological studies on the echolocation system of bats sensitive to Doppler-shifted echoes

Abstract

Rhinolophus ferrumequinum and Pteronotus parnellii emit orientation sounds consisting of a long CF component and a short FM component. The CF component is used for “Doppler-shift compensation.” In rf, the gate used to obtain the frequency information for the compensation is probably opened at the beginning of the sound emission and is closed shortly after the end of the emission. The cricothyroid muscle is highly developed and its activity decreases proportionately with the amount of Doppler-shift compensation. These bats have peripheral auditory systems highly specialized for the reception of the CF component in orientation signals. The extent of cortical representation of the peripheral sensory field depends on its important for species behavior. In p. p., neurons processing the CF components in the orientation signal and Doppler-shifted echoes occupy a disproportionately large part of the auditory cortex. The separate FM signal processing area is also large. This disproportionate cortical representation related to features of biologically significant signals is comparable to that found in the somato-sensory and visual systems in many mammals. [Work supported by NSF.]