A comparison of sniff bottle staircase and olfactometer-based threshold tests.

Olfactometers have been gaining popularity as research tools, but they have yet to replace established testing procedures in a variety of laboratory and clinical settings, including absolute threshold tests. In this research, we designed and operated a simple olfactometer with which to assess threshold. To do this, we used a method-of-adjustment test that was compared to the three-alternative forced choice ascending sniff bottle staircase method, which is currently a standard threshold test procedure. We found that the olfactometer threshold test correlated highly with the staircase method, and that it possessed suitable test-retest reliability. The advantages of the olfactometer threshold test include faster test time and reduced cleaning and reassembly demands. Future use of the olfactometer in olfactory identification and/or detection thresholds amongst odors is also outlined.

Evaluation of smoking on olfactory thresholds of phenyl ethyl alcohol and n-butanol.

The effect of smoking on the sense of smell remains inconclusive. Previous research suggests that this is due to idiosyncratic acuity dependent on the odorants used in testing. Specifically, it appears that smokers have reduced olfactory acuity to odorants found within cigarettes compared with odorants not within cigarettes. Given that some of these odorants are used in tomography and magnetic resonance imaging, an in-depth understanding of this phenomenon in smoking individuals is crucial. This study assesses the variation of olfactory thresholds in smokers based on selective impairment to two odors commonly used in olfactory testing - n-butanol and phenyl ethyl alcohol (PEA). We presented to 46 participants an 18 step, forced choice, three choice ascending staircase method sniff bottle threshold test using n-butanol and PEA. PEA is present in cigarettes while n-butanol is not. Therefore n-butanol is used as a covariate to control for variance explained by any general olfactory dysfunction. Using this method, we can focus solely on selective impairment. We discovered that n-butanol threshold scores were significantly different between smokers and nonsmokers. In addition, after using n-butanol as covariate, phenyl ethyl alcohol scores remained significantly different between groups. This data suggests that there is an extended impairment to odors within tobacco and this may explain a cause of the inconclusiveness of past research.

Tests for screening olfactory and gustatory function in school-age children.

OBJECTIVE: Determine the suitability of three tests based on the identification of familiar odors and tastes for the clinical assessment of olfaction and gustation in children. STUDY DESIGN AND SETTING: A total of 232 children aged 5 to 7 years from Sydney public schools and 56 adults aged 18 to 51 years participated in a cross-sectional study. RESULTS: The children demonstrated they can identify the majority of the 16 test odorants and 4 common tastes that describe gustatory function. The response distributions obtained for each test provide the basis for a set of normative data for young children. CONCLUSION: Olfactory and gustatory function can be determined in school-age children using the three tests described. SIGNIFICANCE: Currently no satisfactory clinical tests of olfaction and gustation for children or normative data are available. The present study resolves these shortcomings and provides normative data that can be used in the diagnosis of olfactory and gustatory impairment in school-age children.

Relationship between molecular structure, concentration and odor qualities of oxygenated aliphatic molecules.

Increasing the concentration of an odorant increases the number of receptor cells and glomeruli in the olfactory bulb that are stimulated, and it is commonly acknowledged that these represent increased numbers of receptor types. Currently, it is not known whether a receptor type is associated with a unique quality and a unique molecular feature of an odorant, or its activation is used by the brain in a combinatorial manner with other activated receptor types to produce a characteristic quality. The present study investigated the proposal that a molecular feature common to several aliphatic odorants and known to be the key feature required to stimulate the same mitral cells in the olfactory bulb results in a quality that is common to the odorants. Since the common structural feature may activate a specific receptor type possibly at a similar concentration, the qualities of the odorants were determined at seven concentrations where the lowest and highest concentrations were the detection threshold (DT) and 729DT of each subject. A list of 146 descriptors was used by 15 subjects to describe the qualities of each odorant at each concentration. The results indicate that each of the five odorants was characterized by different qualities and the qualities of four of the odorants changed with changes in concentration. Importantly, no quality common to each of the odorants that had the same molecular feature could be identified and it is proposed that identification of the odorants occurs via a combinatorial mechanism involving several types of receptors.

Identification of the components of taste mixtures by adults and children.

Recently, it was reported that cognitive factors may have impeded the analysis of binary taste mixtures by 8- to 9-year-old children, resulting in them identifying only the strongest component in each mixture compared to adults who identified both components (Oram, Laing, Freeman, & Hutchinson, 2001). The current study aimed to overcome this limitation by employing different training procedures and different instructions when conducting the task. In particular, the training involved familiarization with the two stimuli at several levels of perceived intensity to facilitate identification of the varying levels of each stimulus in mixtures. Using a selective attention procedure, adults and children were required to identify the components of stimuli that contained water, sucrose (sweet), sodium chloride (salty), or were binary mixtures of these two tastants. Both groups were successful in identifying the component(s) in each stimulus, demonstrating the importance of appropriate training and test procedures when studying the sensory responses of children. Together with data from the earlier study by Oram et al. (2001) it is concluded that 8- to 9-year-olds have the cognitive skills to analyze taste mixtures in terms of the identity of the components and their perceived strengths.

Modulation of anxiety-related behaviours following lesions of the prelimbic or infralimbic cortex in the rat.

A series of experiments examined behavioural and autonomic aspects of stress and anxiety in rats subjected to either: (1) electrolytic lesions of the infralimbic cortex subregion of the medial prefrontal cortex; (2) electrolytic lesions of the prelimbic cortex subregion of the medial prefrontal cortex; (3) sham lesions of infralimbic or prelimbic cortex (sham control); or (4) no lesions (control). In exploration-based models of anxiety, infralimbic- or prelimbic-lesioned rats spent less time in the centre of an open field and less time on the exposed arms of an elevated plus maze, indicating increased anxiety. Locomotor activity was normal in the lesioned rats when tested in a non-stressful enclosed environment. In a step-down passive avoidance task, infralimbic-lesioned rats stepped down more quickly than controls onto a grid floor where they had been shocked 24 h previously. Prelimbic-lesioned rats were no different to controls on this test, although they showed greater latencies to step down onto the grid floor during conditioning. In a final experiment, indirect calorimetry was used to show that both infralimbic- and prelimbic-lesioned rats have essentially normal alterations in oxygen consumption and energy substrate utilisation when exposed to brief footshock. Thus, the impaired passive avoidance in infralimbic-lesioned rats cannot be attributed to decreased nociception. It is concluded that both the prelimbic and infralimbic regions play a role in anxiety, and that this role may be subtly differentiated. In particular, the infralimbic cortex may have a specific role in mediating the inhibition of behaviours associated with aversive outcomes.