02217nas a2200169   4500008004100000245007100041210006900112520157100181653001401752653002401766653002401790653001501814653002201829653001601851100002601867856015401893       2002                        eng d00aPhysiology of the Auditory Afferents in an Acoustic Parasitoid Fly0 aPhysiology of the Auditory Afferents in an Acoustic Parasitoid F3 a<p>The fly, Ormia ochracea, possess a novel auditory organ, which allows it to detect airborne sounds. The mechanical coupling of its pair of tympanal membranes provides the basis for a unique means of sensing the direction of a sound source. In this study, we characterized the neuroanatomy, frequency tuning, and neurophysiological response properties of the acoustic afferents. Our experiments demonstrate that the fly&#39;s nervous system is able to encode and localize the direction of a sound source, although the binaural auditory cues available in the acoustic sound field are miniscule. Almost all of the acoustic afferents recorded in this study responded to short and long sound pulses with a phasic burst of one to four action potentials. A few afferents responded tonically for the duration of the sound stimulus. A prominent class of afferents responds to suprathreshold stimuli with only a single spike discharge, independent of stimulus level, frequency, or duration. We also tested the response of the afferents to speakers separated by 180&deg; along the azimuth of the fly. We found that the afferent responses have a shorter latency because of ipsilateral stimulation. This could be a temporal code of the direction of a sound source. The threshold frequency tuning for the afferents revealed a range of sensitivities to the frequency of the cricket host&#39;s calling song frequency. The difference in the number of afferents above threshold on either side of the animal is a population code, which can also be used for sound localization.</p>
10aarthropod10adirectional hearing10amechanical coupling10aparasitoid10apopulation coding10atime coding1 aOshinsky, Michael, L.  uhttp://www.jneurosci.org/lookup/doi/10.1523/JNEUROSCI.22-16-07254.2002https://syndication.highwire.org/content/doi/10.1523/JNEUROSCI.22-16-07254.2002