Cricket song characteristics
Beyond other possibilities of recognising the conspecific calling song temporal
pattern recognition of sound signals is realised in group of insects. Field
cricket males produces sound signals consisting of a 4.5 - 5 kHz carrier
frequency. These song consists of chirps each of them consists of 4 syllables.
In recent studies it was shown that a syllable repetition interval (SRI) of 35
ms is most effective in mate attraction (fig. 1). The question we address in the
current study is what is the underlying neuronal mechanism most likely involved
in recognition of this temporal code shown in fig. 2. The duration of the syllable
itself is given by the duty cycle, which is the percentile quantity of the ratio
between sound and silence.
Brain Neurons
Neuronal processing of sound starts at the receptor site, where the tympanal vibration is transformed into spike trains
of receptor cells each of them sensitive a typical frequency of the sound. Interestingly, not the frequency composition
is used for intraspecific song recognition, but the repetitive syllable interval (SRI)as shown by behavioural analysis.
Ascending neurons 1 and 2 (AN1 und AN2)
have dendritic fields at the auditory neuropile in the prothoracial ganglion. The axons of these neurons project into
the cricket brain. The neuronal activity of these neurons reflect the syllable composition of the chrips and thereby temporal
code of the 'calling song'. The AN1 cell is responding with about 20 spikes upon a single conspecific chirp of 60dB. We
idealised this spike response in our computer simulation with 4 spikes representing one syllable.
Conspecific 'calling song' recognition
is most likely realised in the brain of the cricket, as shown by a work of Klaus Schildberger 1985. He identified
brain neurons in the cricket brain able to produce a characteristic
response (neuronal discharge)upon SRI variation. The identified neuron BNC2b was found to exhibit high pass filter
characteristics more active with short intervals. The brain neuron BNC1c fullfils lowpass filter chracteristics more active
with long intervals. At least, the neuron BNC2a is realising a band-pass filter (in term of syllable repetition interval)
with maximal discharge at the conspecific SRI.
For further information we refer to course literature of the Cornell University
Neuronal Mechanisms of temporal pattern recognition
The response to the conspecific cricket song implies a recognition of the SRI at the neuronal level. The exact mechansism
responsible for conspecific sound recognition is still not known. However, from the basis of neuronal information processing
there are neuronal mechanisms and neuronal architecture suggested able to perform the recognition of the conspecific song.
We therefore designed proposed computer models and tested them for the ability of conspecific song recognition in noisy
habitats. We used the realistic neural model simulation software Genesis. All cells were modeled with a dendrite of 500 µm of 2 µm diameter and an axon of 300 µm with a diameter of 3 µm.
These dimensions idealise the morphology of the brain neurons, which can be seen above. Simulations were performed with
varying SRI's at a fixed duty cycle of 50%.
1. Common element hypothesis (mainly Hoy
et. al.)
2. The delay line hypothesis (mainly Reiss et al.)
3. The rebound effect hypothesis (personal communication
with H.Roemer)
4. The
Anded High and Low Pass Filter (mainly Schildberger et al.)
Authors: Mag. Manfred Hartbauer
DI Robert Legenstein
