The central acoustic tract and audio-vocal coupling in the horseshoe bat, Rhinolophus rouxi

Doppler shift compensation (DSC) behaviour in horseshoe bats is a remarkabl e example of sensorimotor feedback that stabilizes the echo frequency at th e bat's optimum hearing range regardless of motion-induced frequency shifts in the echoes. Searching for a related neural interface, the nucleus of th e central acoustic tract (NCAT) was investigated in the echolocating horses hoe bat, Rhinolophus rouxi, using various neurophysiological and tracer met hods. The NCAT receives bilateral auditory input from the cochlear nuclei a nd sends projections to regions outside the classical acoustic pathway like the pretectal area or the superior colliculus. The binaural input is excit atory from the contralateral and inhibitory from the ipsilateral ear to 53% of the units, and auditory responses were biased to frontal and contralate ral directions. The best frequencies of NCAT neurons match a narrow range a bove;the main frequency component of the bat's species-specific echolocatio n call (62% of the units), and the neurons exhibit extremely sharp tuning ( Q(10dB) up to 632). DSC is degraded by unilateral electrical or pharmacolog ical microstimulation of the NCAT, and heavily impaired by unilateral lesio n of the region. Altogether, the efferents of the NCAT to prevocal areas, t he tuning of its neurons to the DSC-relevant echo frequency range, and the possibility to affect DSC by manipulation of the NCAT, support the assumpti on that the nucleus plays an important role in audio-vocal control in the h orseshoe bat.