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The Journal of Neuroscience, June 29, 2005, 25(26):6137-6144; doi:10.1523/JNEUROSCI.0646-05.2005

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Behavioral/Systems/Cognitive
Effect of the Temporal Pattern of Contralateral Inhibition on Sound Localization Cues

Gary Marsat and Gerald S. Pollack

Department of Biology, McGill University, Montreal, Quebec, Canada H3A1B1

We studied the temporal coding properties of identified interneurons in the auditory system of crickets, using information theory as an analytical tool. The ascending neuron 1 (AN1), which is tuned to the dominant carrier frequency (CF) of cricket songs, selectively codes the limited range of amplitude modulation (AM) frequencies that occur in these signals. AN2, which is most sensitive to the ultrasonic frequencies that occur in echolocation calls of insectivorous bats, codes a broader range of AM frequencies, as occur in bat calls. A third neuron, omega neuron 1 (ON1), which is dually tuned to both ranges of carrier frequency, was shown previously to have CF-specific coding properties, allowing it to represent accurately the differing temporal structures of both cricket songs and bat calls. ON1 is a source of contralateral inhibition to AN1 and AN2, enhancing binaural contrast and facilitating sound localization. We used dichotic stimulation to examine the importance of the temporal structure of contralateral inhibition for enhancing binaural contrast. Contralateral inhibition degrades the coding of temporal pattern by AN1 and AN2, but only if the temporal pattern of inhibitory input matches that of excitation. Firing rate is also decreased most strongly by temporally matched contralateral inhibition. This is apparent for AN1 in its mean firing rate; for AN2, high-frequency firing is selectively suppressed. Our results show that the CF-specific coding properties of ON1 allow this single neuron to enhance effectively localization cues for both cricket-like and bat-like acoustic signals.

Key words: cricket; temporal coding; auditory; information theory; phonotaxis; communication

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Received Feb 17, 2005; revised May 16, 2005; accepted May 17, 2005.

This article has been cited by other articles:

				G. S. Pollack and R. Martins Flight and hearing: ultrasound sensitivity differs between flight-capable and flight-incapable morphs of a wing-dimorphic cricket species J. Exp. Biol., September 15, 2007; 210(18): 3160 - 3164. [Abstract] [Full Text] [PDF]

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				M. J. Chacron Nonlinear Information Processing in a Model Sensory System J Neurophysiol, May 1, 2006; 95(5): 2933 - 2946. [Abstract] [Full Text] [PDF]

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