CENTRAL MECHANISMS OF PARALLEL INFORMATION PROCESSING
IN THE MOTH AUDITORY SYSTEM (LEPIDOPTERA, NOCTUIDAE)
Noctuid moths (Lepidoptera, Noctuidae) are able to detect bats by listening
to their echolocation calls. When exposed to loud ultrasound that corresponds
to a predator approaching moths demonstrate unpredictable evasive maneuvers.
Since several bats could hunt simultaneously at the same site, to be able to
listen out for each of them is critically important to a moth. The current
study examines the principles of parallel processing of independent rhythmic
signals in the central parts of moth auditory system.
Moths were presented with two continuous trains of ultrasonic (40 kHz carrier) pulses of different repetition rate (this kind of stimulation imitated the echolocation signals of two bats). The responses were recorded from auditory interneurons by means of microelectrodes.
It was found that within the interval when the next pulse would have appear (according to each of the two stimulation trains) interneurons demonstrated higher sensitivity (the emphasis zones). Along with higher sensitivity zones the intervals with abrupt response decrease were observed (the suppression or rejection zones).
One could interpret the emphasis zones as an evidence of expectant attention paid by a moth to the signals of a bat. The appearance of moments of attention should cause the suppression zones to develop in parallel.