Representation of acoustic communication signals by insect auditory receptor neurons
Christian K. Machens, Martin B. Stemmler, Petra Prinz, Rüdiger Krahe, Bernhard Ronacher & Andreas V. M. Herz
Journal of Neuroscience 21: 3215-3227 (2001)
Abstract
Despite their simple auditory systems, some insect species
recognize certain temporal aspects of acoustic stimuli with an
acuity equal to that of vertebrates; however, the underlying
neural mechanisms and coding schemes are only partially
understood. In this study, we analyze the response characteristics
of the peripheral auditory system of grasshoppers with special
emphasis on the representation of species-specific communication
signals. We use both natural calling songs and artificial random
stimuli designed to focus on two low-order statistical properties
of the songs: their typical time scales and the distribution of
their modulation amplitudes.
Based on stimulus reconstruction techniques and quantified within
an information-theoretic framework, our data show that artificial
stimuli with typical time scales of >40 msec can be read from
single spike trains with high accuracy. Faster stimulus variations
can be reconstructed only for behaviorally relevant amplitude
distributions. The highest rates of information transmission (180
bits/sec) and the highest coding efficiencies (40%) are obtained
for stimuli that capture both the time scales and amplitude
distributions of natural songs.
Use of multiple spike trains significantly improves the
reconstruction of stimuli that vary on time scales <40 msec or
feature amplitude distributions as occur when several grasshopper
songs overlap. Signal-to-noise ratios obtained from the
reconstructions of natural songs do not exceed those obtained from
artificial stimuli with the same low-order statistical
properties. We conclude that auditory receptor neurons are
optimized to extract both the time scales and the amplitude
distribution of natural songs. They are not optimized, however, to
extract higher-order statistical properties of the song-specific
rhythmic patterns.
Last modified: Fri Nov 28 11:24:07 CET 2008