THE PROCESSING OF A MIXTURE OF TWO RHYTHMIC SIGNALS BY THE AUDITORY
SYSTEM IN NOCTUID MOTHS (LEPIDOPTERA, NOCTUIDAE)
We have reported earlier that the responses of auditory interneurons essentially
depends on the number of independent acoustic signals arriving at the ears
of a noctuid moth (Lapshin, 2010). These results
were obtained as a response to stimulation consisting of two trains of tonal
pulses which had almost similar frequency and temporal parameters.
The next stage of our work was to check whether the same kind of responses will remain when the two stimulation signals will be significantly different: i.e. when they will vary in pulse period and frequency spectrum.
In the present study the responses of prothoracic interneurons of noctuid moths (Noctuidae) to the mixture of two rhythmic signals were recorded. Both signals were a pulse trains; first with a tonal (40 kHz) pulses and second with a noise-filled (35-120 kHz) pulses. The characteristics of the noise pulses were selected to be similar to the natural noise produced during a moth's flight and were presented as a background stimulation. It was found that the auditory system of noctuid moths is able to detect tonal signals having 30-100 times lower amplitude than the background rhythmic noise.