Chem. Senses 27: 23-29,
2002
© Oxford University Press 2002
Olfactory Discrimination Ability for Aromatic Odorants as a Function of Oxygen Moiety
Department of Medical Psychology, University of Munich Medical School, Goethestraße 31, D-80336 Munich, Germany
Correspondence to be sent to: Matthias Laska, Institut für Medizinische Psychologie, Ludwig-Maximilians-Universität, Goethestraße 31, D-80336 München, Germany. e-mail: laska{at}imp.med.uni-muenchen.de
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Abstract |
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 Top Abstract IntroductionExperiment 1: discriminability...Experiment 2: trigeminality of...DiscussionReferences |
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To assess the significance of the type of oxygen moiety on odor quality of aromatic compounds, I tested the ability of human subjects to distinguish between odorants sharing a benzene ring and the same total number of carbon atoms but differing in their functional groups. Phenyl ethanol, phenyl acetaldehyde, phenyl methyl ketone, methyl benzoate and phenyl acetic acid, were employed. In a forced-choice triangular test procedure 20 subjects were repeatedly presented with all possible binary combinations of the five odorants, and asked to identify the bottle containing the odd stimulus. I found (i) that as a group, the subjects performed significantly above chance level in six of the tasks whereas they failed to do so with the four other tasks; (ii) marked interindividual differences in discrimination performance, ranging from subjects who were able to significantly distinguish between all 10 odor pairs to subjects who failed to do so with the majority of the tasks; and (iii) that odor pairs that involved methyl benzoate or phenyl methyl ketone were significantly easier to discriminate than those that involved phenyl acetaldehyde or phenyl ethanol, and thus there was a clear dependence of discriminability on type of functional group. Additional tests of the degree of trigeminality of the five aromatic substances indicated that the discriminability of the odor pairs is indeed due to differences in odor quality. A comparison of the present results with those of an earlier study that employed aliphatic odorants suggests that functional oxygen-containing groups may generally be an important determinant of the interaction between the stimulus molecule and the olfactory receptor, and thus may generally be a molecular property affecting odor quality in a substance class-specific manner. The poorer discriminatory performance of the subjects with aromatic odorants compared with corresponding aliphatic substances suggests that the structure of the alkyl rest attached to a functional group may also play a crucial role for recognition of ligands at the olfactory receptor and thus for odor quality.
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Introduction |
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TopAbstractIntroductionExperiment 1: discriminability...Experiment 2: trigeminality of...DiscussionReferences |
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The multidimensionality of the chemical world presents a real challenge to the olfactory system of any species. However, most of the animal species investigated so far are capable of perceiving and discriminating between a large variety of odors (Hildebrand and Shepherd, 1997
). This raises the question of how the olfactory
system achieves this—in some cases amazingly well
developed—ability to recognize different odor qualities.
It is now widely agreed that the cascade of events leading to odor
recognition begins with differential interaction of odor molecules with
different types of olfactory receptors
(Malnic et al.,
1999). It is also widely accepted that both the overall shape and
size of an odor molecule as well as the nature and disposition of its
functional group(s) play a crucial role in the interaction occurring between
stimulus and receptor (Weyerstahl,
1994; Rossiter,
1996).
Although a considerable number of psychophysical studies have tried to
reveal, and have generally reported, some correlations between odor quality
and molecular properties (Pilgrim and
Schutz, 1957; Moskowitz and
Barbe, 1977; Dravnieks,
1985; Jeltema and Southwick,
1986; Cain et al.,
1998), most of these studies have failed to provide quantitatively
useful data as they have usually relied on enumerative description and thus
have a strong subjective component, have an unproven ability to discern small
differences and are indeterminate regarding the extent of individual
differences (Wise et al.,
2000).
Recently, Laska and colleagues have begun to systematically assess odor
structure—activity relationships using discrimination procedures which
avoid the disadvantages of subjectivity, context dependence and poor
resolution, allow for examination of individual differences and yield
non-negotiable answers with potential archival value
(Laska and Freyer, 1997; Laska
and Teubner, 1998,
1999a,
b; Laska et al.,
1999,
2000). With regard to the
first structural feature determining the degree of interaction between
stimulus and olfactory receptor—overall size and shape of the
molecule—they could show a significant negative correlation between
olfactory discrimination performance (and thus odor quality) and structural
similarity of odorants in terms of differences in carbon chain length in all
major classes of oxygen-containing aliphatic compounds.
With regard to the second structural feature affecting the strength and
character of odorants—nature and disposition of functional
group(s)—Laska et al.
(Laska et al., 2000)
have recently shown human subjects to have a well-developed ability to
discriminate between aliphatic odorants sharing the same number of carbon
atoms but differing in their oxygen moieties. Further, they demonstrated that
functional groups affected odor quality in a substance class-specific
manner.
In an extension of this study I decided to test the ability of human subjects to distinguish between aromatic odorants that are identical in structure except for their oxygen moieties. The aim of this was to help clarify whether the correlation between type of functional group and olfactory discriminability found with aliphatic odorants could also be found with substances sharing a benzene ring rather than a linear and unbranched carbon chain. Further, a comparison of the results of the present study and the earlier one should help to evaluate the impact of the structure of the alkyl rest on discriminability and thus odor quality.
Thus, the aims of the present study are twofold: (i) to provide data on the olfactory discrimination ability of human subjects for aromatic odorants sharing the same number of carbon atoms but differing in their functional groups; and (ii) to assess whether the effect of type of oxygen moiety on discriminability and thus odor quality of aromatic odorants is substance-class specific.
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Experiment 1: discriminability of odorants |
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TopAbstractIntroductionExperiment 1: discriminability...Experiment 2: trigeminality of...DiscussionReferences |
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Materials and methods
Human subjects
A total of 20 healthy, unpaid volunteers (two males and 18 females), 23-39
years of age (median = 28 years), participated in the study. None of the
subjects had any history of olfactory dysfunction. They were informed as to
the aim of the experiment and provided written consent. The study was
performed in accordance with the Declaration of Helsinki/Hong Kong.
Odorants
A set of five odorants was used (Table
1). They comprised aromatic substances sharing the same number of
carbon atoms but differing in their oxygen moiety (alcohol, aldehyde, ketone,
carboxylic acid and ester, respectively). All substances were obtained from
Merck (Darmstadt, Germany) and had a nominal purity of at least 99%. They were
diluted using diethyl phthalate (Merck) as the solvent. In an attempt to
ensure that the odorants were of approximately equal strength when presented
in squeeze bottles, intensity matching was performed by a panel of six
subjects using a 8.7 g/l solution of isoamyl acetate as the reference and
adopting a standardized psychophysical procedure
(ASTM, 1975).
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Test procedure
A 20 ml aliquot of each odorant was presented in a 250 ml polyethylene
squeeze bottle equipped with a flip-up spout. Subjects were instructed as to
the manner of sampling and at the start of the first session were allowed time
to familiarize themselves with the bottles and the sampling technique. Care
was taken that the flip-up spout was only a short distance (1-2 cm) from the
nasal septum during sampling of an odorant in order to allow the stimulus to
enter both nostrils.
In a forced-choice triangular test procedure 20 subjects were asked to
compare three bottles and identify the one containing the odd stimulus
(Lawless and Heymann, 1998).
Additionally, after each decision, subjects were asked whether their choice
was based predominantly on perceived differences in odor quality or on
perceived differences in odor intensity. Each bottle could be sampled twice,
with an inter-stimulus interval of 10 s. Sampling duration was restricted to 1
s per presentation in order to minimize adaptation effects. The sequence of
presentation of the stimulus pairs was systematically varied between sessions
and individual subjects, while taking care that the presentation of a given
odorant as the odd or even stimulus was balanced within and between sessions.
In order to control for possible cross-adaptation effects, the order in which
the stimuli of a given triad were sampled was systematically varied between
sessions. Approximately 30 s were allowed between trials and no feedback
regarding the correctness of the subjects' choice was given.
Ten different stimulus pairs, i.e. all possible binary combinations of the five odorants, were presented twice per session, and testing was repeated in four more sessions each 1-3 days apart, enabling 10 judgements per stimulus pair and panelist to be collected.
Data analysis
The criterion for an individual subject to be regarded as capable of
discriminating a given odor pair was set at seven or more out of 10 decisions
correct (two-tailed binomial test, P < 0.05). Accordingly, the
criterion for the group of subjects to be regarded as capable of
discriminating a given odor pair was set at 13 or more out of 20 subjects
performing significantly above chance (two-tailed binomial test, P
< 0.01).
Comparisons of group performance across tasks were made using the Friedman
two-way analysis of variance (ANOVA). When the ANOVA detected differences
between tasks, this was then followed by pairwise Wilcoxon signed-rank tests
for related samples to evaluate which tasks were involved
(Siegel and Castellan, 1988).
Frequencies in discrete categories were compared using the 
2
test. All data are reported as mean ± SD.
Results
General discrimination performance
Figure 1. summarizes the
mean performance of 20 subjects in discriminating between the 10 odor pairs.
As a group, the human subjects performed significantly above chance level in
six of the 10 tasks, whereas they failed to do so with the remaining four
tasks. Interindividual variability was high, particularly in odor pairs that
more than a few of the panelists were unable to distinguish above chance (cf.
SDs in Figure 1). However, the
ANOVA detected significant differences in the group's performance between
tasks (Friedman, P < 0.001) and subsequent pairwise tests revealed
that the four odor pairs that were not discriminated above chance at the group
level (1-2, 1-5, 2-5 and 3-4; cf. Table
1) were significantly more difficult to distinguish compared with
the six odor pairs which the group of subjects were able to discriminate
(Wilcoxon, P < 0.05 for all pairs). Accordingly, only 1-5 out of
20 subjects failed to significantly distinguish between the latter group of
odor pairs, whereas 9-17 out of 20 subjects were unable to discriminate the
former group of odor pairs. With only few exceptions (which always involved
odor pair 2-3), the odor pairs that were significantly discriminated at the
group level did not differ significantly from each other in their degree of
discriminability (Wilcoxon, P > 0.05). Similarly, with only few
exceptions (which always involved odor pair 1-5), the odor pairs that were not
significantly discriminated at the group level did not differ significantly
from each other in their degree of discriminability (Wilcoxon, P >
0.05).
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Discriminability of the individual odorants
Figure 2 illustrates the
discriminability of the individual odorants. The number of times that a given
odorant was involved when subjects failed to significantly discriminate an
odor pair (Figure 2, lower
panel) ranged from only 14 with odor no. 4 (methyl benzoate) to 39 with odor
no. 2 (phenyl acetaldehyde) and thus differed significantly between stimuli
(2, P < 0.05). Likewise, the mean scores of
correct decisions across the four tasks that involved a given odorant
(Figure 2, upper panel)
differed significantly between stimuli (Friedman, P < 0.05).
Subsequent pairwise comparisons revealed that odor no. 4 (methyl benzoate) was
more readily discriminated than the four other odorants (Wilcoxon, P
< 0.05), and that odor no. 3 (phenyl methyl ketone) was more readily
discriminated than odors no. 1 (phenyl ethanol) and no. 2 (phenyl
acetaldehyde).
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Interindividual differences
Interindividual differences in subjects' ability to discriminate between
the 10 odor pairs were quite large. The percentage of errors ranged from only
11% for the best-performing subject up to 41% for the worst. Accordingly, the
best panelist was able to significantly distinguish all 10 odor pairs whereas
the poorest-performing subject failed to do so with six of the 10 tasks.
Training effects
The mean performance of the group of 20 subjects across the five test
sessions was quite stable. Error rates did not differ significantly between
sessions (Friedman, P > 0.05), and thus no training or learning
effects at the group level were found.
Odor intensity
With all 10 odor pairs <16% of decisions were reported to be based upon
perceived differences in odor intensity rather than odor quality (cf. Test
procedure). Altogether, 91.0% of decisions were reported to be based upon
perceived differences in odor quality.
None of the statistical comparisons mentioned above led to significantly different results when the decisions reported to be based upon perceived differences in odor intensity rather than odor quality were removed from the data set.
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Experiment 2: trigeminality of odorants |
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TopAbstractIntroductionExperiment 1: discriminability...Experiment 2: trigeminality of...DiscussionReferences |
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The results of experiment 1 showed that the ability of human subjects to discriminate between aromatic substances on the basis of differences in oxygen moiety was substance specific.
In order to elucidate whether the nasal trigeminal system contributed to
this performance, I assessed whether the substances differ in their degree of
trigeminality by testing subjects' ability to localize the side of monorhinal
stimulation. This simple method has been shown adequate to reliably quantify
the trigeminal impact of odorants (Berg
et al., 2000).
Materials and methods
Subjects
A total of 10 healthy, unpaid volunteers (two males and eight females),
23-39 years of age (median = 27 years), participated in the study. All
subjects had already participated in experiment 1. They were chosen on the
basis of availability and not on the basis of their performance in the
previous experiment.
Odorants
The same set of five odorants as in experiment 1 was used
(Table 1). The substances were
diluted using diethyl phthalate (Merck) as the solvent to the same
concentrations as in experiment 1.
Test procedure
Using a custom-made squeezer, air from two 250 ml polyethylene squeeze
bottles was applied to the right and the left nostril of a subject. One bottle
contained 40 ml of an odorant whereas the other bottle contained 40 ml of the
odorless solvent. Both bottles were equipped with a flip-up spout which for
testing was fitted with a handmade Teflon nose-piece. Care was taken that the
nose-pieces were in direct contact with the nostrils during sampling in order
to ensure that each stimulus entered one nostril only. Presentation of an
odorant was synchronized with the subject's inhalation and the squeezer was
calibrated to deliver 20 ml of air to each nostril.
In a forced-choice test procedure 10 subjects were asked to identify the side of stimulation with an odorant. The sequence of presenting the stimuli was systematically varied between sessions and individual subjects while taking care that the presentation of a given odorant to the left or the right nostril was balanced within and between sessions. Approximately 30 s were allowed between trials and no feedback regarding the correctness of the subjects' choice was given. The five stimuli were presented five times per session and testing was repeated in three more sessions, each 1-3 days apart, enabling 20 judgements per stimulus and panelist to be collected.
Data analysis
The criterion for an individual subject to be regarded as capable of
localizing the side of monorhinal stimulation with a given odorant was set at
14 or more out of 20 decisions correct (two-tailed binomial test, P
< 0.05). Accordingly, the criterion for the group of subjects to be
regarded as capable of localizing a given odorant was set at eight or more out
of 10 subjects performing significantly above chance (two-tailed binomial
test, P < 0.05).
Comparisons of group performance across tasks and sessions were made using
the Friedman two-way analysis of variance. When the ANOVA detected differences
between tasks or sessions, this was then followed by pairwise Wilcoxon
signed-rank tests for related samples to evaluate which tasks or sessions were
involved (Siegel and Castellan,
1988). All data are reported as mean ± SD.
Results
General localization performance
Figure 3 summarizes the mean
performance of 10 subjects in localizing the side of monorhinal stimulation
with phenyl ethanol, phenyl acetaldehyde, phenyl methyl ketone, methyl
benzoate and phenyl acetic acid when presented at the same concentrations as
in experiment 1. As a group, the human subjects clearly failed to perform
significantly above chance in all five tasks, with 8-10 out of 10 individuals
not reaching the criterion of at least 14 out of 20 decisions correct.
Accordingly, an ANOVA failed to find significant differences in group
performance between tasks (Friedman, P > 0.05).
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Interindividual differences
Interindividual differences in subjects' ability to localize the side of
monorhinal stimulation were comparatively small (cf. SDs in
Figure 3), and altogether there
was only one case of an individual subject scoring 80% correct choices
(corresponding to a 1% level of significance) with one of the five substances
(methyl benzoate). The percentage of overall correct choices ranged from 63%
for the best-performing subject to 44%. Even the best panelist was only able
to localize two out of five substances at a 5% level of significance, whereas
the majority of subjects failed to do so with all five tasks.
Training effects
The mean performance of the group of 10 subjects across the four test
sessions was quite stable. Error rates did not differ significantly between
sessions (Friedman, P > 0.05), and thus no training or learning
effects at the group level were found.
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Discussion |
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TopAbstractIntroductionExperiment 1: discriminability...Experiment 2: trigeminality of...DiscussionReferences |
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The results of this study demonstrate that the ability of human subjects to discriminate between aromatic odorants sharing the same number of carbon atoms but differing in their oxygen moieties is (i) clearly dependent on the type of functional group involved; and (ii) poorer than that for corresponding aliphatic substances (Laska et al., 2000
). Prior to a discussion of these findings, it seems appropriate to consider whether the performance of the human subjects shown in the present study was indeed based on the ability of the olfactory system to discern between odor qualities, or whether other sensory systems or other talents of the olfactory system may have been involved.
The possibility that the nasal trigeminal system might have contributed to
the discrimination of odorants (Doty,
1995) can be excluded for two reasons: firstly, recent
psychophysical studies have shown nasal pungency thresholds, mediated by the
trigeminal nerve, of human subjects to be generally at least two and up to
four orders of magnitude higher than odor thresholds, mediated by the
olfactory nerve (Cometto-Muniz and Cain,
1995; Cometto-Muniz et al.,
1998a,
b). Thus, although congenitally
anosmic subjects have been shown to possess at least a coarse ability to
distinguish between highly concentrated odorants using information provided by
their fifth cranial nerve (Laska et
al., 1997), the dilutions employed here (cf.
Table 1) are likely to prevent
trigeminal involvement in the discrimination of stimuli. Secondly, the results
of experiment 2 clearly demonstrate that the substances used here had little,
if any, trigeminal-stimulating properties at the concentrations tested and
that in any case the stimuli did not differ in their degree of
trigeminality.
Although the possibility that differences in perceived odor intensity might
have contributed to the discrimination performance cannot be ruled out
completely, this seems quite unlikely as the attempt to present stimuli at
equal subjective intensities was confirmed by the fact that in the critical
discrimination tasks >90% of the subjects' decisions were reported to be
based on perceived differences in odor quality rather than odor intensity (cf.
Test procedure). Further, the few instances in which perceived differences in
odor intensity were reported seem to mirror a subject's difficulty to
discriminate at all, as error rates in such cases tended to be higher than the
usually reported differences in odor quality. The same tendency for higher
error rates with reports of perceived differences in odor intensity rather
than odor quality as a choice criterion has been found in studies assessing
the discriminability of members of homologous series of aliphatic compounds
(Laska and Freyer, 1997; Laska
and Teubner, 1998,
1999b;
Laska et al., 1999)
and of terpenes (Laska and Teubner,
1999a). Therefore, it seems reasonable to assume that the
discrimination scores found here reflect the ability of the human olfactory
system to distinguish between odor qualities.
The most important finding of the present study is that the ability of human subjects to distinguish between aromatic odorants solely on the basis of oxygen-containing functional groups is clearly substance-class specific. It was apparent that the aromatic ester and ketone were more easily discriminated from the other stimuli than aromatic substances with the same number of carbon atoms but with a functional alcohol or aldehyde group (cf. Figures 1 and 2).
Exactly the same rank order of discriminability as in the present study,
ketone 
carboxylic acid > alcohol aldehyde, was found in a recent
study that employed the same paradigm with aliphatic (rather than aromatic)
odorants sharing the same number of carbon atoms and differing only in their
oxygen moiety (Laska et al.,
2000). Here, too, the odor pair ketone versus carboxylic acid was
most readily distinguished, and the odor pairs alcohol versus aldehyde and
aldehyde versus carboxylic acid yielded the lowest percentages of correct
discriminations. Unfortunately, esters were not included in that study.
However, in contrast to the earlier study, in which all odor pairs tested were
clearly discriminable above chance at the group level, the present study
showed that several combinations presented considerable difficulties to the
subjects and were not discriminated above chance (cf.
Figure 1). This suggests that
both the oxygen moiety and the molecular structure of the alkyl
rest—straight-chained in the case of the aliphatic substances, ring-like
in the case of the aromatic substances—affects discriminability and thus
odor quality of the stimuli. Recent studies using optical imaging techniques
lend support to this supposition as they, too, have reported both molecular
structural features mentioned to be important for odor recognition in
olfactory systems as diverse as those of mammals
(Uchida et al., 2000)
and insects (Sachse et al.,
1999) at the level of the first olfactory neuropil, i.e. the
olfactory bulb and the antennal lobe, respectively.
Although I cannot rule out completely the possibility that the poor discriminability of the odor pair phenyl acetaldehyde versus phenyl acetic acid may, at least in part, be due to the fact that the former substance is rather unstable in the presence of oxygen and easily converted to the latter substance, this seems unlikely as the subjects' discriminatory performance with this odor pair did not deteriorate across sessions but was poor from the start.
One hypothetical explanation for the corresponding substance
class-specificity of discriminability and thus qualitative similarity observed
with both aliphatic and aromatic substances is that the presence of certain
oxygen moieties, such as an ester or keto group, might lead to more specific
interactions with olfactory receptors, and/or that stimulus molecules bearing
such functional groups might interact with a smaller subset of receptors
compared with stimuli with functional alcohol or aldehyde groups. This idea is
supported by electrophysiological findings that show that certain odor
molecules interact with a larger number of olfactory receptors than others
(Sicard and Holley, 1984). The
molecular mechanism possibly underlying this phenomenon is related to
differences in the dipole qualities of the oxygen moieties, as keto or
carboxylic groups, for example, are stronger dipoles than alcohol groups when
attached to the same alkyl radical (Beets,
1982).
One possible means to test this hypothesis is to assess the molecular
receptive ranges of identified olfactory receptors for sets of substances that
are similar to the one employed here using cellular recording techniques. The
recently accomplished cloning, functional expression and characterization of
olfactory receptor types in rats (Zhao
et al., 1998) and humans
(Hatt et al., 1999)
provide the tool with which to perform such studies.
At the level of the olfactory bulb, Katoh et al.
(Katoh et al., 1993)
recorded responses from rabbit single mitral cells following stimulation with
a set of aromatic compounds with various substituents and found a clear
dependence of response patterns on type of functional group. Although the
authors mainly employed non-oxygen-containing substituents, their findings are
in line with the present results as they, too, point to a key role for dipole
quality of functional groups in the interaction between stimulus and
receptor.
The finding of the present study that the olfactory discriminability of
aromatic substances on the basis of oxygen moiety was markedly poorer than
that for corresponding aliphatic substances
(Laska et al., 2000)
may, at least in part, be explained by the fact that the ring-like structure
of aromatic compounds leads to more stable and thus less flexible molecular
conformations than the linear backbone of aliphatic compounds. As the
interaction of an odor molecule with an olfactory receptor is considered to be
a multipoint attachment process (Ohloff,
1994), the higher flexibility of a straight-chained alkyl rest
should allow for more options of hydrogen bonding than a stiff, ring-like
alkyl rest (Afshar et al.,
1998). This supposition is supported by theoretical considerations
that emphasize the role of both flexibility and overall structure of apolar
parts of an odor molecule for the specificity of the directed
dipole—dipole interaction or hydrogen bonding underlying the interaction
between stimulus and receptor (Yoshii and
Hirono, 1996; Chastrette and
Rallet, 1998).
Taken together, the findings of the present study provide evidence for a clear dependence of olfactory discriminability of aromatic substances on type of oxygen moiety. In agreement with an earlier study that employed aliphatic substances, the results support the assumption that functional oxygen-containing groups may generally be an important determinant of the interaction between stimulus molecule and olfactory receptor, and therefore may generally be a molecular property affecting odor quality in a substance-class-specific manner. At the same time, a comparison of the results of the two studies shows that the structure of the alkyl rest attached to a functional group may also play a crucial role in the recognition of ligands at the olfactory receptor and thus of odor quality.
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Acknowledgments |
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I thank the panelists for their willingness to participate in this study, and the Deutsche Forschungsgemeinschaft for financial support (La 635/10-1).
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References |
|---|
|
TopAbstractIntroductionExperiment 1: discriminability...Experiment 2: trigeminality of...DiscussionReferences |
|---|
Afshar, M., Hubbard, R.E. and Demaille, J. (1998) Towards structural models of molecular recognition in olfactory receptors. Biochimie, 80,129 -135.[Medline]
ASTM (1975) Standard recommended practice for referencing suprathreshold odor intensity. Am. Soc. Testing Materials (Phil.), E, 544-575.
Beets, M.G.J. (1982) Odor and stimulant structure. In Theimer, E.T. (ed.), Fragrance Chemistry—The Science of the Sense of Smell. Academic Press, New York, pp.77 -122.
Berg, J., Hummel, T., Huamg, G. and Doty, R.L. (2000) Trigeminal impact of odorants assessed with lateralized stimulation. Chem. Senses,25 , 793-794.
Cain, W.S., de Wijk, R.A., Lulejian, C., Schiet, C. and
See, L.C. (1998) Odor identification: perceptual and
semantic dimensions. Chem. Senses,23
, 309-326.
Chastrette, M. and Rallet, E. (1998) Structure—minty odour relationships: suggestion of an interaction pattern. Flavor Fragr. J., 13,5 -18.
Cometto-Muniz, J.E. and Cain, W.S.
(1995) Relative sensitivity of the ocular trigeminal, nasal
trigeminal and olfactory systems to airborne chemicals. Chem.
Senses, 20,191
-198.
Cometto-Muniz, J.E., Cain, W.S. and Abraham, M.H. (1998a) Nasal pungency and odor of homologous aldehydes and carboxylic acids. Exp. Brain Res.,118 , 180-188.[Web of Science][Medline]
Cometto-Muniz, J.E., Cain, W.S., Abraham, M.H. and Kumarsingh, R. (1998b) Trigeminal and olfactory chemosensory impact of selected terpenes. Pharmacol. Biochem. Behav., 60,765 -770.[Web of Science][Medline]
Doty, R.L. (1995) Intranasal trigeminal chemoperception. In Doty, R.L. (ed.), Handbook of Olfaction and Gustation. Marcel Dekker, New York, pp.821 -833.
Dravnieks, A. (1985) Atlas of Odor Character Profiles. American Society for Testing and Materials, Philadelphia, PA, Data Series 61.
Hatt, H., Gisselmann, G. and Wetzel, C. (1999) Cloning, functional expression and characterization of a human olfactory receptor. Cell. Mol. Biol.,45 , 285-291.[Web of Science][Medline]
Hildebrand, J.G. and Shepherd, G.M. (1997) Mechanisms of olfactory discrimination: converging evidence for common principles across phyla. Annu. Rev. Neurosci., 20,595 -631.[Web of Science][Medline]
Jeltema, M.A. and Southwick, E.W. (1986) Evaluation and applications of odor profiling. J. Sens. Stud., 1,123 -136.
Katoh, K., Koshimoto, H., Tani, A. and Mori, K.
(1993) Coding of odor molecules by mitral/tufted cells in
rabbit olfactory bulb. II. Aromatic compounds. J.
Neurophysiol., 70,2161
-2175.
Laska, M. and Freyer, D. (1997)
Olfactory discrimination ability for aliphatic esters in squirrel monkeys
and humans. Chem. Senses, 22,457
-465.
Laska, M. and Teubner, P. (1998)
Odor structure—activity relationships of carboxylic acids correspond
between squirrel monkeys and humans. Am. J. Physiol.,274
, R1639-R1645.
Laska, M. and Teubner, P. (1999a)
Olfactory discrimination ability of human subjects for ten pairs of
enantiomers. Chem. Senses, 24,161
-170.
Laska, M. and Teubner, P. (1999b)
Olfactory discrimination ability for homologous series of aliphatic
alcohols and aldehydes. Chem. Senses,24
, 263-270.
Laska, M., Distel, H. and Hudson, R.
(1997) Trigeminal perception of odorant quality in
congenitally anosmic subjects. Chem. Senses,22
, 447-456.
Laska, M., Trolp, S. and Teubner, P. (1999) Odor structure—activity relationships compared in human and non-human primates. Behav. Neurosci.,113 , 998-1007.[Web of Science][Medline]
Laska, M., Ayabe-Kanamura, S.,
Hübener, F. and Saito, S.
(2000) Olfactory discrimination ability for aliphatic
odorants as a function of oxygen moiety. Chem. Senses,25
, 189-197.
Lawless, H.T. and Heymann, H. (1998) Discrimination testing. In Lawless, H.T. and Heymann, H. (eds.),Sensory Evaluation of Food—Principles and Practices . Chapman & Hall, London, pp. 117-139.
Malnic, B., Hirono, J., Sato, T. and Buck, L.B. (1999) Combinatorial receptor codes for odors.Cell , 96,713 -723.[Web of Science][Medline]
Moskowitz, H.R. and Barbe, C.D. (1977) Profiling of odor components and their mixtures. Sens. Processes, 1,212 -226.[Web of Science][Medline]
Ohloff, G. (1994) Scent and Fragrances. The Fascination of Odors and their Chemical Perspectives. Springer, Berlin.
Pilgrim, F.J. and Schutz, H.G. (1957) Measurement of the quantitative and qualitative attributes of flavor. In Chemistry of Natural Food Flavors. Quartermaster Food Container Institute, Chicago, IL, pp.47 -58.
Rossiter, K.J. (1996) Structure—odor relationships. Chem. Rev., 96,3201 -3240.[Web of Science][Medline]
Sachse, S., Rappert, A. and Galizia, C.G. (1999) The spatial representation of chemical structure in the antennal lobe of honeybees: steps towards the olfactory code.Eur. J. Neurosci. , 11,3970 -3982.[Web of Science][Medline]
Sicard, G. and Holley, A. (1984) Receptor cell responses to odorants: similarities and differences among odorants. Brain Res., 292,283 -296.[Web of Science][Medline]
Siegel, S. and Castellan, N.J. (1988)Nonparametric Statistics for the Behavioral Sciences . McGraw-Hill, New York.
Uchida, N., Takahashi, Y.K., Tanifuji, M. and Mori, K. (2000) Odor maps in the mammalian olfactory bulb: domain organization and odorant structural features. Nature Neurosci., 3,1035 -1043.[Web of Science][Medline]
Weyerstahl, P. (1994) Odor and structure. J. Prakt. Chem., 336,95 -109.
Wise, P.M., Olsson, M.J. and Cain, W.S.
(2000) Quantification of odor quality. Chem.
Senses, 25,429
-443.
Yoshii, F. and Hirono, S. (1996)
Construction of a quantitative three-dimensional model for odor quality
using Comparative Molecular Field Analysis (CoMFA). Chem.
Senses, 21,201
-210.
Zhao, H., Ivic, L., Otaki, J.M., Hashimoto, M., Mikoshiba,
K. and Firestein, S. (1998) Functional expression
of a mammalian odorant receptor. Science,279
, 237-242.
Accepted September 6, 2001
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