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Animal Olfaction -
Quantifying Capabilities
Background:
Jim Walker began his
work on what is termed animal olfactory psychophysics as a graduate
student. He was blessed with having something of a triumvirate of
professors. Jim Smith, who began his career a bit before Jim entered
the world, transmitted a great deal of knowledge and practical insight
as to the core principles of obtaining solid data for a wide variety
of combinations of species and sensory modalities. From Dr. Smith, Jim
also learned a great deal about the need to know the scientific
literature extremely well, to listen closely to the insights of animal
learning/behavior colleagues, to be scrupulously attentive to all
experimental details and to take pains to write with clarity and to
“let the data speak for themselves”. From Mike Rashotte, Jim
learned an enormous amount about theory and practice in the animal
learning area; much of the insight gleaned under Mike’s tutelage
made its way into animal methods Jim went on to develop. Don Tucker
taught Jim about the structure and function of the vertebrate
olfactory system, the principles underlying air dilution olfactometry,
the technique of recording activity from the olfactory nerve and the
art of picking apart manuscripts and published work in all areas of
olfaction.
In chronological order, some key accomplishments of Jim’s in this
area may be noted:
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Use of
conditioned suppression procedure to determine if odor quality
discrimination is possible in pigeons deprived entirely of
olfactory input to the brain.
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Development and
use of operant task (symmetrical response contingencies, no
aversive stimulation, animal’s nares kept in stimulus airstream)
to measure odor sensitivity in pigeons and then track return of
normal sensitivity with nerve reconstitution and reinnervation
following transection.
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Development and
use of cardiac conditioning approach to quantify odorant
sensitivity to several odorants in pigeons before vs. after
resection (removal) of the olfactory nerve (leaving only
trigeminal input to mediate detection).
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Development
(with R. J. O’Connell) and use of automated procedures for
training and testing of odor sensitivity in mice. (This study was
the first report in which quantitative thresholds were determined
in mice).
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Development and
use of new methodology that, for the first time, quantified
sensitivity in dogs that were treated the same as those used in
applied settings (no food or water deprivation, housed with owners
vs. lab-housed, dog and handler working together in team manner).
NOTE: At b-Noses, the only line of experimental data collection
planned is that outlined in item #5.
Sample (hypothetical)
Projects/Issues:
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Our laboratory
would like to establish the capability to quantify olfactory
prowess in rats in a set of tasks that include threshold testing
and 2-odor quality discrimination. This is needed so that we can
study the effects of various pharmacological agents on each
olfactory task and generate new information needed to advance the
field of sensory coding. It is essential that no aversive
stimulation be employed in training or testing, that symmetrical
response contingencies be employed, that training be completely
automated and that the data be transparently comparable to those
from other species (including humans). We seek assistance in
establishing the basic methodology, working out procedures for
data processing (including assessment of variation) and
interpretation of drug effects.
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Our laboratory
has been asked to participate in a team effort to relate odor
processing ability to odorant receptor (OR) genes in mice, dogs
and humans. Our laboratory is to be in charge of the mice and dog
data. We seek assistance in setting up training and testing
procedures in both species so that: a) techniques used for control
of stimulus concentration (and other parameters) are highly
precise for both species and provide control comparable to that to
be achieved with human participants; b) behavioral procedures for
determining the limits of various olfactory functions in dogs and
mice are such that comparisons between these two species are may
be made with confidence (“apples to apples”) and data from
both are easily related to humans.
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For largely
applied reasons, my research group needs to quantify the
sensitivity of the trigeminal nerve in several species of birds to
a set of 20 compounds presented in vapor phase. It is extremely
important that: a) we select a psychophysical or
psychophysiological (e.g. cardiac conditioning) procedure that is
useful with all species in providing a whole organism measure of
trigeminal nerve activation; b) the concentration of each compound
be precisely controlled within and between species; c) we
determine the threshold of each bird to at least ½ of the set of
20 compounds; and d) the results be related to other measures of
nasal irritation (including in humans) and to physicochemical
parameters (e.g., in a QSAR modeling program). We seek help in
selecting and applying all aspects of the methodology, writing up
and executing the research plan, developing optimal approaches for
data processing and interpretation as well as the
presentation, publication and dissemination of results.
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I am in charge
of R&D for a company that performs detector dog services for
government and industry and supplies dogs for use by a
variety of organizations. I have been tasked with devising and
implementing a program that our company will use to: a) verify
that each dog meets a variety of performance standards when
presented with precisely controlled odor stimuli; b) characterize
each dog in terms of stability of performance over days as well as
the amount of time it can be expected to work at odor tasks of
varying difficulties; iii) identify dogs that do not perform at
criterion levels of reliability; iv) establish an advantage over
our competitors; v) compare breeds of dogs as well as dogs within
breed on a variety of tests; and vi) assess the merits of various
training approaches as ways to improve field performance. I seek
assistance with all aspects of this important new effort.
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I represent a
research organization that wishes to exploit the plasticity of the
olfactory system of the bird to shed some light on sensory coding
questions. We would like to be able to characterize each bird on a
range of odor psychophysical tests, then do a variety of surgical
manipulations, repeat the pre-surgical testing and then sacrifice
the animal to describe the pattern of reinnervation of olfactory
bulb by reconstituted olfactory neurons. For example, we want to
determine which capabilities are affected by various kinds of
“abnormal” rearrangements of the connections between the
olfactory periphery and bulb and by reductions in the amount of
total input to the bulb. We would like assistance with the
selection of the testing protocols, the control of odorant
concentrations, the processing of psychophysical data, the
surgical procedures to produce various “rewirings” of the
system and techniques to verify that these rearrangements took
place.
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I represent an
international entity that does cooperative research to optimize
the value of animal olfaction for applied uses such as mine
detection, drug detection and search and rescue operations. We
have become interested in two related questions: i) Can we use
exposure to selected odorants to increase or decrease sensitivity
to those odorants?; and ii) Can we do the same thing via
“vascular smell” (causing odorants to be more or less
continuously present in the bloodstream)? Our hope is that we can
first determine the direction of the change, if any, that exposure
(whether via the air or via vascular route) causes and then use
that to improve performance of animals used to detect, recognize
and localize odor sources in the field. We would like to be able
to compare both methods, on a within-species basis, in terms of
the effect on performance, with respect to particular chemicals.
We seek assistance with the selection of animals for this work,
the methods used to control chemical concentrations as well as
circulating levels of chemicals, the psychophysical methods used
to assess performance and methods for processing and interpreting
data.
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I am the head of
a group that has received a great deal of funding to take work
over the past 2-3 decades on the synaptic organization and
neurochemistry of the mammalian olfactory bulb, develop hypotheses
as to which pharmacological agents will alter different aspects of
information processing in this structure, design a range of
psychophysical tests of a variety of aspects of olfactory function
and then conduct work to quantify effects of each agent on each
olfactory capability. It is essential that this work be of such
quality that it will stand up well to any intellectually honest
scrutiny. Thus we must be scrupulous in stimulus control, wise in
the selection of behavioral/psychophysical methods and careful in
our experimental design and statistical procedures. We seek
assistance with all aspects of the planning, execution and
presentation/publication of this project.
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