Sound-sensitive neurons innervate the ventro-lateral protocerebrum of the heliothine moth brain
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Many noctuid moth species perceive ultrasound via tympanic ears that are located at the metathorax. Whereas the neural processing of auditory information is well studied at the peripheral and first synaptic level, little is known about the features characterizing higher order sound-sensitive neurons in the moth brain. During intracellular recordings from the lateral protocerebrum in the brain of three noctuid moth species, Heliothis virescens, Helicoverpa armigera and Helicoverpa assulta, we found an assembly of neurons responding to transient sound pulses of broad bandwidth. The majority of the auditory neurons ascended from the ventral cord and ramified densely within the anterior region of the ventro-lateral protocerebrum. The physiological and morphological characteristics of these auditory neurons were similar. We detected one additional sound-sensitive neuron, a brain interneuron with its soma positioned near the calyces of mushroom bodies and with numerous neuronal processes in the ventro-lateral protocerebrum. Mass-staining of ventral-cord neurons supported the assumption that the ventro-lateral region of the moth brain was the main target for the auditory projections ascending from the ventral cord.
KeywordsAuditory ventral-cord neurons Iontophoretic staining Brain targeted region Ultrasound Noctuid moths
We thank Jan Tro, Yan Jiang and Tim Cato Netland (Department of Electronics and Telecommunications, NTNU) for assisting us with measurement of the acoustic signals. We also thank Dr. Pal Kvello and Dr. Bjarte Bye Løfaldli (Kavli Institute, NTNU) for assistance with the AMIRA reconstructions. We are grateful to Syngenta (Basel, Switzerland) and Dr. Jun-Feng Dong (Henan University of Science and Technology, Henan, China) for sending insect pupae.
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