My
group conducts research that combines anatomical, behavioral,
chemical, and neurophysiological methods in a multidisciplinary
approach to problems of the organization, physiology, functions,
and postembryonic development of the insect nervous system. The
main goal of this work is to discover fundamental principles and
mechanisms common to many or all nervous systems through studies
of the experimentally favorable nervous systems of insects. In
view of the importance of insects in their own right, we also
aim to
contribute to knowledge that will help to alleviate the harm done
by insects that are predators of the human food supply or vectors
of diseases. Areas of our principal interest currently include:
the physiology, functional organization, and postembryonic development
of the olfactory system; sensory control of mating behavior and
insect-host interactions, including feeding and oviposition behaviors;
chemical ecology and behavioral aspects of moth-hostplant interactions;
olfactory learning and the roles of biogenic amines in plasticity
of olfactory function; and functional organization of neurosecretory
systems.
Functional
organization and physiology of the insect olfactory system. We
study the olfactory system of the giant sphinx moth Manduca
sexta . Using intracellular and staining methods, extracellular
and multi-unit recording techniques, and pharmacological manipulations,
we explore the neuronal circuitry and synaptic interactions in
the antennal lobe (AL), the primary olfactory center in the moth's
brain. We also use histological and neuronal tracing methods to
learn about the anatomical organization of the AL and its sensory
inputs. Our goal is to understand cellular mechanisms of information
processing in the olfactory pathways in the CNS. Much of our work
has focused on the sexually dimorphic olfactory subsystem in the
male moth that is specialized to detect and process information
about the female's sex pheromone. We also conduct multi-level
studies of the detection and central processing of information
about volatile compounds emitted by living plants. In addition
to our primary focus on the AL, we are very interested in the
higher-order olfactory pathways in the protocerebrum that are
involved in processing of the outputs of the ALs and their integration
with information of other modalities.
Postembryonic,
metamorphic development of the olfactory system. We have long
been interested in neural development and plasticity in the ALs
during the postembryonic development of Manduca . We
have shown that certain, sexually dimorphic glomeruli characteristic
of male and female ALs develop only if the AL is innervated, respectively,
by axons of genetically male or female olfactory receptor cells.
In a continuing collaboration among members of my group and faculty
colleagues Leslie Tolbert, Lynne Oland, Alan Nighorn and their
coworkers, a multidisciplinary quest for the cellular and molecular
mechanisms underlying these and other aspects of AL development
is in progress.
Behavior
and chemical ecology. In parallel with our studies of the olfactory
system of Manduca , we are investigating the chemical
composition of the volatiles emitted by living host- and nonhost
plants and using a variety of chemical, physiological and behavioral
methods to identify behaviorally significant compounds in those
complex mixtures. In addition, we are exploring the roles of CO
2 in moth-plant interactions, and we conduct detailed studies
of the effects of odors on the behavior of flying Manduca
in the field and in laboratory wind tunnels.
Organization and functions
of neurosecretory systems. We have a long-standing interest in
the identification, metabolism, and cellular localization
of neuroeffectors
(e.g. neurotransmitters, neuromodulators, neurohormones) in insects.
Our current efforts focus on the functional organization of
neurosecretory
cells in the CNS that express neuropeptides and polypeptide neurohormones
and on the roles of such cells in the control of organ function
and behavior of the insect.
Selected
Recent Publications
Guerenstein PG, Hildebrand JG. Dec 2007. Roles and effects of environmental carbon dioxide in insect life. Annu Rev Entomol, 53:161-78
Dacks AM Christensen TA Hildebrand JG. Oct 2006. Phylogeny of a serotonin-immunoreactive neuron in the primary olfactory center of the insect brain. J Comp Neurol, 498:727-46
Davis NT, Hildebrand JG. Mar 2006. Neuroanatomy of the sucking pump of the moth, Manduca sexta (Sphingidae, Lepidoptera). Arthropod Struct Dev, 35:15-33
Dacks AM, Christensen TA, Agricola HJ, Wollweber L, Hildebrand JG. Aug 2005. Octopamine-immunoreactive neurons in the brain and subesophageal ganglion of the hawkmoth Manduca sexta. J Comp Neurol, 488:255-68
Reisenman CE, Christensen TA, Hildebrand JG. Aug 2005. Chemosensory selectivity of output neurons innervating an identified, sexually isomorphic olfactory glomerulus. J Neurosci, 25:8017-26
Lei H, Christensen TA, Hildebrand JG. Dec 2004. Spatial and temporal organization of ensemble representations for different odor classes in the moth antennal lobe. J Neurosci, 24:11108-19
Gibson NJ, Hildebrand JG, Tolbert LP. Aug 2004. Glycosylation patterns are sexually dimorphic throughout development of the olfactory system in Manduca sexta. J Comp Neurol, 476:1-18
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