Biomedical subjects

Matthias Laska

Publications and source records attributed to Matthias Laska.

24 records · Page 2Linked to original sources

PubMed2003

SURE, why not? The SUbstitution-REciprocity method for measurement of odor quality discrimination thresholds: replication and extension to nonhuman primates.

Recently, Olsson and Cain (2000, Chem. Senses, 25: 493) introduced a psychometric method which, for the first time, allows the standardized determination of odor quality discrimination (OQD) thresholds. The method defines a threshold value that is an average fraction by which one odorant has to be substituted with another to reach a criterion level of discrimination. This measure of discrimination is reciprocal in the sense that it is a result of two separate psychometric functions involving two different standards but the same comparison stimuli. Using the same odor stimuli as Olsson and Cain, with six human subjects but adopting a slightly different experimental design, we were able to replicate their finding that the proportion of correct discriminations changes monotonically with the proportion of adulterant in mixtures of eugenol and citral. As the SURE (SUbstitution-REciprocity) method is based on discriminative responses, it should also be applicable with nonhuman species which can be trained to give unequivocal discriminative responses at the behavioral level. Using an olfactory conditioning paradigm, we therefore trained four squirrel monkeys to discriminate between exactly the same pairs of odor stimuli as our human subjects. We found the psychometric functions of the monkeys to be similar to those of the human subjects. Our results show that the SURE method can successfully be employed with nonhuman primates and thus offers a new approach to study the odor spaces of nonhuman species. Future studies should elucidate whether the SURE method allows for direct comparisons of OQD thresholds and of similarities and differences between odor quality perception of different species.

Acyclic Monoterpenes↗

PubMed2002

Olfactory sensitivity for aliphatic esters in squirrel monkeys and pigtail macaques.

Using a conditioning paradigm, the olfactory sensitivity of four squirrel monkeys and three pigtail macaques for a homologous series of aliphatic esters (ethyl acetate to n-octyl acetate) and isomeric forms of some of these substances were investigated. With only few exceptions, all animals of both species significantly discriminated concentrations below 1 ppm from the odorless solvent, and in several cases, individual monkeys even demonstrated thresholds below 1 ppb. The results showed (a) both primate species to have an unexpectedly high olfactory sensitivity for aliphatic esters, which for the majority of substances matches or even is better than that of species such as the rat, the mouse, or the dog; (b) squirrel monkeys to generally perform better than pigtail macaques in detecting aliphatic esters; and (c) a significant negative correlation between perceptibility in terms of olfactory detection thresholds and carbon chain length of the n-aliphatic esters in both species tested. These findings support the assumptions that between-species comparisons of neuroanatomical features are a poor predictor of olfactory performance and that general labels such as 'microsmat' or 'macrosmat'--which are usually based on allometric comparisons of olfactory brain structures--are inadequate to describe a species' olfactory capabilities.

Animals↗

PubMed2002

Deviant olfactory experiences, magical ideation, and olfactory sensitivity: a study with healthy German and Japanese subjects.

Little is known about the relationship between olfactory hallucinations and olfactory sensitivity in psychiatric populations. However, in healthy subjects, a 'psychotic-like' feature, namely magical ideation, has been linked to deviant olfactory experiences. We thus assessed olfactory sensitivity, magical ideation and deviant olfactory experiences in 42 healthy subjects (21 Germans and 21 age- and gender-matched Japanese). The results show that: (1) Germans had significantly higher magical ideation scores and a higher frequency of deviant olfactory experiences than Japanese, and more Germans than Japanese reported having had deviant olfactory experiences at least once in their lives; (2) in Germans, the occurrence of deviant olfactory experiences was correlated with higher magical ideation scores; and (3) there was no relationship between olfactory sensitivity (olfactory thresholds) and either deviant olfactory experiences or magical ideation, respectively. We conclude that: (1) the lack of deviant olfactory experiences in Japanese may best be explained by cultural differences in the response attitude towards questionnaires requiring self-disclosure; (2) the positive relationship between magical ideation and deviant olfactory experiences strengthens the supposed link between 'psychotic-like' features in healthy populations and real hallucinations of psychiatric patients; and (3) the absence of a relationship between olfactory sensitivity and deviant olfactory experiences suggests that their anatomical-functional correlates within temporo-limbic regions may differ.

Adult↗

PubMed2002

Gustatory responsiveness to food-associated saccharides in European rabbits, Oryctolagus cuniculus.

Taste preference thresholds for six food-associated saccharides and relative sweet-taste preferences were assessed in 12 European rabbits using two-bottle choice tests of brief duration (3 min). In Experiment 1, the animals were found to significantly prefer concentrations as low as 30 mM maltose, 50 mM polycose and sucrose, 75 mM glucose, 150 mM fructose, and 175 mM lactose over tap water. In Experiment 2, the rabbits were given a choice between all binary combinations of the same six saccharides presented in equimolar concentrations of 100 and 200 mM. Preferences for individual saccharides were stable across the concentrations tested and indicate the following order of relative effectiveness: maltose=polycose>sucrose>glucose>fructose > or =lactose. The results showed rabbits to display a pattern of taste preference thresholds and relative taste preferences for food-associated saccharides similar to that found in rodents but differing markedly from that found in human and nonhuman primates. The results support the assumptions that rabbits, unlike most primates, but similar to rodents, may have specialized taste receptors for starch, and that the gustatory responsiveness of Oryctolagus cuniculus to food-associated saccharides might reflect an evolutionary adaptation to its dietary habits.

Animals↗

PubMed2002

Olfactory discrimination ability for aromatic odorants as a function of oxygen moiety.

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.

Adult↗

PubMed2002

Olfactory sensitivity for aliphatic alcohols in squirrel monkeys and pigtail macaques.

The view that primates are microsmatic animals is based mainly on an interpretation of neuroanatomical features, whereas physiological evidence of a poorly developed sense of smell in this order of mammals is largely lacking. Using a conditioning paradigm, we therefore assessed the olfactory sensitivity of three squirrel monkeys (Saimiri sciureus) and of four pigtail macaques (Macaca nemestrina) for a homologous series of aliphatic alcohols (ethanol to 1-octanol) and isomeric forms of some of these substances. In the majority of cases, the animals of both species significantly discriminated concentrations below 1 part per million from the odourless solvent, and with 1-hexanol individual monkeys even demonstrated thresholds below 10 parts per billion. The results showed (i) that both primate species have a well-developed olfactory sensitivity for aliphatic alcohols, which for the majority of substances matches or even is better than that of species such as the rat, (ii) that both species generally show very similar olfactory detection thresholds for aliphatic alcohols, and (iii) that a significant negative correlation between perceptibility in terms of olfactory detection threshold and carbon chain length of both the aliphatic 1- and 2-alcohols exists in both species. These findings support the idea that across-species comparisons of neuroanatomical features are a poor predictor of olfactory performance and that general labels such as 'microsmat' or 'macrosmat', which are usually based on allometric comparisons of olfactory brain structures, are inadequate to describe the olfactory capabilities of a species. Further, our findings suggest that olfaction may play an important and hitherto underestimated role in the regulation of behaviour in the species tested.

1-Butanol↗