Meeting Abstract

P3.91  Jan. 6  Anti-directional processing of auditory information in the praying mantis YAGER, D.D.**; DIGIOVANNI, P.; SMITH, E.; Univ. of Maryland, College Park; Univ. of Maryland, College Park; Univ. of Maryland, College Park ddyager@umd.edu

With one exception, all animals that hear have two ears. The information from the two ears is kept separate in the CNS, and left-right (L-R) differences are often enhanced. This is the basis for directional hearing. Praying mantids have a single ear in the midline of the metathorax comprising an auditory chamber with a tympanum in each lateral wall. Each hemi-ear reports to the CNS via a tympanal nerve. Sound triggers a fast evasive maneuver that very effectively protects mantids from capture by attacking bats. We hypothesized that mantids eliminate any L-R differences by mixing the information from both tympanal nerves early in the CNS processing path. This would provide a powerful, highly coordinated signal to the brain. If true, the ascending auditory activity on the two sides of the CNS would be synchronized, possibly on a spike-by-spike basis. We simultaneously recorded the ascending responses to sound of a left-right pair of auditory interneurons. Following 50 stimuli at 20 db over threshold (CONTROL), we cut the tympanal nerve on one side, thus making the input to the CNS highly asymmetrical. Responses to another 50 stimuli (TEST) were then recorded. The nerve transection caused a symmetrical reduction in spike numbers even after compensation for a 4-6 dB elevation of threshold. To assess the level of synchronization between action potentials in the two neurons, we quantified the occurrence of coincident spikes above that expected with a random distribution. Statistical analysis revealed a very high level of spike-by-spike synchronization in the CONTROL condition that persisted in the TEST condition. The two interneurons do not interact and few afferents cross the midline, so intermediary neurons must distribute the auditory signals bilaterally.