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RESEARCH INTERESTS
Neuroethology
Neurophysiology of insect olfaction
Evolution of pheromone production and perception in heliothine moths
Odor-mediated behaviors of moths and other insects
PUBLICATIONS
Poster
Flying electroantennograms: eyes in the sky
For many species of animal the sense of smell is
incredibly important in many life-sustaining activities.
Animals use odors to identify receptive mates, distinguish
friend from foe, and locate suitable prey or host plants.
The ability of male moths to detect minute amounts of
female pheromone and repond by flying upwind is an
extraordinary demonstration of the role that smell can
play in shaping behavior. The existence of an olfactory
system that is accessible to electrophysiological
recording, well-characterized odors, and stereotypical
odor-mediated behaviors make moths a powerful system in
which to investigate the biologically important
phenomenon of olfaction.
The basis for our neuroethological approach is to combine
studies of odor-mediated flight behavior with
neurophysiological investigations of the olfactory system
in several related species of moth. The species that we
use are important agricultural pests raising the
possibility that new understandings arising from our
research will lead to more effective and environmentally
sensitive means of pest control.
Behavioral Studies of Odor-mediated Flight.
As adults, much of the behavioral repertoire of moths
involves odor. Females locate suitable host plants for
oviposition; males and females visit flowers for the
purposes of nectar feeding; and males locate females (and
then often court the female with odor contained in brush
structures located on various parts of their body or
wings). Many of these odor-mediated activities occur over
large distances and involve flight. Because much of the
flight activity is nocturnal, long distance visual cues are
typically unavailable. Instead, odor plays a central role in
modulating and guiding the flight behavior. We use both
wind tunnel and field studies to investigate the behavioral
mechanisms that underlie upwind flight and location of
odor sources. Our studies have revealed that moment to
moment contacts with the odor plume are significant in
shaping male responses to female pheromone. In addition
to the importance of plume structure, upwind flight
behavior is strongly influenced by the chemical content of
the odor signal. Odors are often blends of two or more
different molecules, the ratios of which can be crucial in
determining attractiveness. Furthermore, females of one
species may employ compounds in their pheromone blends
that disrupt the behavior of males of another species. The
manipulation of chemical and temporal features of odor
signals has provided us with important insights into the
behavioral mechanisms that result in upwind flight and
these studies serve as the context for examining the
underlying olfactory neurobiology.
Neurobiology of Olfactory Systems
In the animal kingdom, nose shape and appearance varies
widely. Despite this morphological diversity, the
underlying neuroanatomical organization of the olfactory
epithelium and primary processing center for olfactory
input in the brain is essentially similar. Receptor neurons
located on the periphery (the antenna of many insects)
send axons to a primary processing area in the brain called
the antennal lobe (the functional equivalent of the
olfactory bulb in many other animals). Within this
structure receptor neurons synapse with local and
projection interneurons. Synapses between neurons appear
to be restricted to spheroidal knots of neuropil called
glomeruli. Using glass micro electrodes, single projection
neurons can be impaled and their responses to different
odorants, puffed over the antenna, assayed. By injecting a
fluorescent dye into the neuron following physiological
recording, we can examine the structure of the cell, paying
particular attention to the olfactory glomerulus or
glomeruli that house the cellšs input region. In this way
we are able to correlate the physiological profile of the
neuron with its morphological features. Because
glomeruli are common anatomical features of olfactory
systems from widely divergent animals, we hope that by
understanding how a subset of glomeruli in the relatively
simple male moth olfactory system are organized to
represent the odor world, we will gain a better
understanding of their role in olfaction in general. In the
species of moth studied in our laboratory, we are
beginning to understand that the glomerular organization
of the antennal lobe forms a spatial representation of
chemical content in the olfactory environment. By
monitoring neuronal activity within and across different
subsets of glomeruli, moths appear able to discriminate
between attractive and antagonistic odor blends. In the
future, we hope to ascertain how olfactory information is
integrated in higher brain centers with input from other
sensory modalities, such as vision.
Selected Publications
Hillier, N.K. and Vickers, N.J. 2004. The role of heliothine hairpencil compounds in female Heliothis virescens (Lepidoptera: Noctuidae) behavior and mate acceptance. Chemical Senses 29:499-511.
Baker, T.C., Ochieng', S.A., Cossé, A.A., Lee, S.G., Todd, J.L., Quero, C. and Vickers, N.J. 2004. A comparison of responses from olfactory receptor neurons of Heliothis subflexa and Heliothis virescens to components of their sex pheromone. Journal of Comparative Physiology A. 190:155-165.
Vickers, N.J., Poole, K., and Linn Jr., C.E. 2003. Consequences of interspecies antennal imaginal disc transplantation on organization of olfactory glomeruli and pheromone blend discrimination.
Journal of Comparative Neurology 466:377-388.
Ochieng, S.A., Poole, K., Linn Jr., C.E., Vickers, N.J., Roelofs, W.L., and Baker, T.C. 2003. Unusual pheromone receptor neuron responses in heliothine moth antennae derived from inter-species imaginal disc transplantation. Journal of Comparative Physiology A. 189:19-28.
Vickers, N.J. and Christensen, T.A. 2003. Functional divergence of spatially conserved olfactory glomeruli in two related moth species. Chemical Senses 28:325-338.
Vickers, N.J. 2002. Defining a synthetic pheromone blend attractive to male Heliothis subflexa under wind tunnel conditions. Journal of Chemical Ecology 28: 1267-1279.
Vickers, N.J., Christensen, T.A., Baker, T.C. and Hildebrand, J.G. 2001. Odour-plume dynamics influence the brain's olfactory code. Nature 410: 466-470.
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