Taste and smell function in pediatric blood and marrow transplant patients.

BACKGROUND: The intensive conditioning regimens of a pediatric blood and marrow transplant (BMT) can limit voluntary intake leading to a risk of malnutrition. Poor dietary intake is likely multi-factorial with a change in taste and smell function potentially being one contributing factor limiting intake, though this is not well studied. This research aimed to assess the taste and smell function of a cohort of pediatric BMT patients. METHODS: A total of ten pediatric BMT patients (8-15 years) were recruited to this study. Smell function was assessed using a three-choice 16-item odour identification test. Taste function was assessed using five concentrations of sweet, sour, salty and bitter tastants. All tests were completed at admission to transplant and monthly until taste and smell function had normalised. RESULTS: At the 1-month post-transplant assessment, one third of participants displayed some evidence of taste dysfunction and one third smell dysfunction, but there was no evidence of dysfunction in any patient at the 2-month assessment. CONCLUSION: Contrary to reports of long-term loss of taste and smell function in adults, dysfunction early in transplant was found to be transient and be resolved within 2 months post-transplant in children. Further research is required to determine the causes of poor dietary intake in this population.

Taste disorders in Australian Aboriginal and non-Aboriginal children.

AIM: To assess the prevalence and type of taste disorders in Aboriginal and non-Aboriginal children matched for age, gender and living in the same general and educational environment. METHODS: Taste function was assessed in 432 Aboriginal (n = 166) and non-Aboriginal (n = 266) children aged 8-12 years from six public schools in a rural township using a three-choice taste identification test and a cross-sectional design. RESULTS: The prevalence of taste disorders was very high and significantly more common in Aboriginal (20/166; 12.0%) than in non-Aboriginal (21/266; 7.9%) children. Forty-one children had quality-specific disorders, of whom 27 (65.9%) had sweet disorders. Children often had more than one quality disorder. CONCLUSION: The prevalence of taste disorders in children was high and exceeded the level (4%) designated by the World Health Organisation as requiring immediate action by health authorities. As the cause of the disorders is unknown, there is a need for a wider investigation of the causes and the consequences.

Intranasal trigeminal function in children.

The aim of the study was to investigate trigeminal function in children compared with that of adults. Trigeminal sensitivity was assessed using a lateralization task where participants were requested to identify the side of the nose to which an odorous stimulus was presented. The ability to localize the sensation is largely based on trigeminal function. A total of 344 people participated (191 females, 153 males; mean age 12 y [SD 7 y 9 mo], range 5-54 y). Eucalyptol (EUC) was administered as a mixed olfactory-trigeminal stimulant; phenylethyl alcohol (PEA) was used as a control stimulant with minimal trigeminal impact. In addition, sensitivity to vibration was assessed as a somatosensory control. With regard to all age groups, PEA could not be localized whereas this was easily possible for EUC. However, the ability to localize EUC increased with age, which was not the case for PEA. No sex-related difference was found for odour localization. These results provide data for normal intranasal trigeminal function in children. They also indicate that trigeminal sensitivity is already well-developed in 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.

A psychophysical study of the relationship between temporal processing in odor mixtures and transduction pathways.

Depending on the odorant, transduction during the olfactory reception process is reported to be mediated by the second messengers cyclic adenosine 3',5'-monophosphate (cAMP) or inositol 1,4,5-triphosphate (IP(3)). The present study with humans investigates the relationship between temporal processing in mixtures and the type of transduction process used. The most common outcomes were reciprocal temporal interactions which were primarily dependent on odorant concentration and independent of the type of transduction process. The results are consistent with the bulk of evidence that each receptor neuron commonly has only one type of receptor.

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.

The analysis of odor mixtures by humans: evidence for a configurational process.

Humans have a limited capacity to analyze odor mixtures with three to four being the maximum [Physiol Behav 46 (1989) 809.]. This study investigates the large loss of information about odor identity that occurs in mixtures and aims to determine the information on which identification and failure to identify is based. In Experiment 1, 14 subjects used a selective attention procedure to identify odorants in stimuli consisting of one to four components. As expected, substantial difficulties were encountered in identifying more than two odorants, and chance level scores were obtained for the group for each of the odorants in the quaternary mixture. In Experiment 2, 21 subjects used a profiling procedure consisting of 146 descriptors to describe the odor qualities perceived in the same stimuli used in Experiment 1. The results indicated that for some odorants, loss of a major characteristic quality occurred even in binary mixtures, but that many of the features of some odorants remained in the quaternary mixture. Comparison of the data from the two experiments indicated that identification of most of the prominent qualities of an odorant was not necessarily sufficient for identification of the odorant in a mixture. In contrast, the loss of some prominent features did not always result in non-identification. A configurational hypothesis of olfaction, analogous to that for facial and object recognition, is proposed to account for the data and the processes underlying odor identification in mixtures.

Analysis of taste mixtures by adults and children.

Children at mid-childhood (8-9 years), have limited perceptual-attentional skills to analyze complex stimuli (Shepp, Barrett, & Kolbet, 1987), and little is known of their skills to analyze chemosensory stimuli. Accordingly, this study investigated the ability of adults and 8-9 year old children to perceive tastes in binary mixtures. In Experiment 1, subjects used a selective attention procedure to indicate whether sweet, salty, and sour tastes were present in stimuli consisting of sucrose (sweet), sodium chloride (salty), citric acid (sour), and all possible binary mixtures of these tastants. Adults correctly recognized the two tastes in all mixtures, whilst children recognized only one in each mixture. Children were successful in recognizing sweet in both sweet-containing mixtures and salty in the sodium chloride-citric acid mixture. In Experiment 2, subjects used a similar selective attention paradigm to assess the perceived intensity of the three tastes in the above single and two-component stimuli. Suppression of one or both components was recorded with most mixtures by both age groups. However, with the mixture sodium chloride-citric acid, only the children recorded suppression of sourness, whilst for adults only saltiness was suppressed. In neither mixture containing sourness did children report suppression of sweetness or saltiness. It is concluded that at mid-childhood humans have difficulty analyzing taste mixtures into their components, due to attentional and possibly gustatory shortcomings.

Temporal processing reveals a mechanism for limiting the capacity of humans to analyze odor mixtures.

Humans have great difficulty in analyzing odor mixtures. The present study investigates the role of temporal processing in mixture perception and its impact on human performance. The results indicate that in contrast to binary mixtures, the temporal order of the perception of components and their identity cannot be discerned in ternary mixtures. It is proposed that the primary cause of this inability is slow processing in olfactory working memory which limits the analysis of mixtures to about three components.

The development of meat-eating habits during childhood in Australia.

The development of meat-eating habits of 999 Australian children between 1 and 16 years of age stratified across socioeconomic groups, was determined using a 4-day diary and measurement procedures to document intake. The results indicated that a stable pattern of meat-eating behaviour, as regards the frequency and type of meat eaten was established during the period 1-4 years of age and remained until 10-12 years for males and until at least 14-16 years for females. In contrast, the amount of meat consumed increased with age, the greatest increases occurring with adolescent males who ate the largest amounts of beef, chicken and pork. It is suggested that the early establishment of meat-eating habits may reflect a more general effect that may occur with other types of food.

Perception of sweetness in simple and complex taste stimuli by adults and children.

Currently, there is little information on the ability of children to analyse complex chemosensory stimuli in terms of the presence and magnitude of the components. The present study investigates this question by comparing the ability of 95 adults and 8- to 9-year-olds to estimate the sweetness of several concentrations of sucrose in water and in three foods, namely, orange drink, custard and shortbread biscuits, using a magnitude estimation procedure. The results indicated that similar response functions were produced by adults and children for the sweetness of aqueous solutions of sucrose, custard and biscuits, but not for orange juice, where the functions produced by both female and male children were significantly flatter than those of the adults. Stimulus context may have influenced the ratings of children in the no-sucrose and highest sucrose concentration conditions with two of the foods. The absence of differences between the response functions of the female and male children with all types of stimuli indicated that gender had no influence on their responses. It is concluded that, at mid-childhood, humans are capable of estimating the sweetness of sucrose in foods, but that they have a tendency to limit the range of numbers used in their estimates of sweetness at high concentrations of sucrose in some foods.

A limit in the processing of components in odour mixtures.

We investigated the hypothesis that physiological limitations restrict the ability of humans to identify components in an odour mixture. Subjects were trained to identify the test odours, and were required to detect a single highly familiar odorant in stimuli consisting of one, four, eight, twelve, and sixteen odorants by using a selective-attention procedure. The stimuli were delivered by a computer-controlled sixteen-channel air-dilution olfactometer which provided samples of each of the sixteen odorants to be of equal perceived intensity for each subject. Identification fell to chance level when sixteen odorants were present. It is proposed that the profound loss of information was primarily due to inhibition of olfactory receptor cells by the odorants through competitive mechanisms, and the subsequent loss of odour identity through changes in the spatial code that may be used to identify odorants.

The influence of odor type on the discrimination and identification of odorants in multicomponent odor mixtures.

Using a limited set of odorants, previous studies have indicated that the ability of humans to discriminate and identify the components of olfactory mixtures is limited to approximately four. However, the ability to generalize these results may have been limited by specific neural or cognitive interactions among the particular odorants used. In the present experiment, 41 subjects examined the influence of odor type (different individual odorants), from two very different odor sets, on the perception of the components of complex mixtures. One set contained odors that were selected by an expert panel to blend well in mixtures (good blenders), whereas the other contained odors that blended poorly in mixtures (poor blenders). The stimuli were common, dissimilar odorants of equivalent, moderate intensity, each of which was a single chemical. A computer-controlled air dilution olfactometer delivered a single odorant or a mixture containing up to eight odorants. Although the poor blenders were more easily discriminated, this superiority was displayed within a narrow range, and the ability of subjects to identify mixture components with either odor set was limited to approximately four. The results indicate that, whereas odor type can alter which odorants will be perceived in a mixture, the limited capacity to discriminate mixture components is independent of the type of odorants. These findings are discussed in terms of their implications for olfactory coding.

Infants' consumption of a new food enhances acceptance of similar foods.

The number of feedings needed to increase intake of a novel target food was investigated, and whether exposure effects generalized to other foods in a sample of 4 to 7-month-old infants (N=39). Other foods varied in their similarity to the target food, including the same food prepared by another manufacturer, similar foods (other fruits for infants receiving a target fruit) and a different food (e. g. vegetables for infants receiving a target fruit). Infants were fed the target food once a day for 10 days. Intake was used to indicate acceptance. Results revealed that exposure dramatically increased infants' intake of the target food, from an average of 35-72 g. Intake of the different food was unchanged. Same and similar food intake increased with target food exposure. Intake of the target, same and similar foods nearly doubled to 60 g after one exposure to the target food. These rapid increases in intake contrast the slower changes seen in young children. Results for the other foods suggest that infants may have difficulty discriminating among many foods.

The influence of chemical complexity on the perception of multicomponent odor mixtures.

The present study investigates the hypothesis that complex object odors (odors that emanate from flowers, foods, sewage, etc.) that consist of dozens of odorants are processed and encoded as discrete entities, as if each was a single chemical odor. To test this hypothesis, the capacity of trained subjects to discriminate and identify the components of stimuli consisting of one to eight object odors was determined. The results indicated that subjects could only identify up to four object odors in a mixture, which is similar to earlier findings with mixtures that contained only single chemical odors. The limited capacity was also reflected in the number of odors selected, regardless of whether the choices were correct or incorrect, in confidence ratings, and in decision times. The identification of a limited number of object odors in every mixture that was presented suggests that both associative (synthetic) and dissociative (analytic) processes are involved in the perceptual analysis of odor mixtures.

Temporal processing of odor mixtures reveals that identification of components takes precedence over temporal information in olfactory memory.

Temporal processing of binary mixtures results in odorants being perceived in series separated by many hundreds of milliseconds. Since the odorant perceived first is the main suppressor, knowledge of the order of perception of two odorants can allow prediction of interactions in mixtures. The present study investigated the temporal coding of ternary mixtures composed of carvone, coniferan and triethylamine, and citralva, lillial and triethylamine using a specially constructed air-dilution olfactometer. The results indicated that even though each of the components could be readily identified in ternary mixtures, it was very difficult to indicate which odor was perceived first, with chance scores being recorded. The same outcome occurred even when the 'slowest' odorant was delivered 600 ms after the 'fastest' to the nose. It is proposed that olfactory memory gives precedence to identification of the components of mixtures rather than to their order of perception when more than two odorants are in a mixture.

A comparison of the ability of 8-9-year-old children and adults to detect taste stimuli.

Conflicting data exist in the literature regarding the maturity of the human sense of taste during childhood and if gender influences gustatory development. To investigate these 2 questions, taste detection thresholds for the 4 common tastants sucrose, sodium chloride, citric acid, and caffeine were established for 61 young adults and 68 children aged 8-9 years old, using a paired-comparison forced-choice procedure. No significant differences were found between the mean thresholds of women and men, or between those of female children and adults. In contrast, male children had significantly higher thresholds for all 4 tastants than adult females, for all tastants except caffeine than adult men, and for sucrose and sodium chloride than female children. It is concluded that the taste sensitivity of 8-9-year-old males, although well developed, has not fully matured, and that taste sensitivity is not affected by gender in young adults.

Detection and discrimination of propionic acid after removal of its 2-DG identified major focus in the olfactory bulb: a psychophysical analysis.

Prior 2-deoxyglucose and c-fos studies have demonstrated increased metabolic activity in a rostral dorsomedial area of the olfactory bulb in response to the vapor of propionic acid. We used psychophysical tests to assess the effect of removing this area of the bulb on odor sensitivity and discrimination. Normal rats, those with lesions of the rostral dorsomedial bulb or with control lesions of the lateral olfactory bulb were tested for propionic acid absolute detection and intensity difference thresholds and ability to discriminate propionic acid from other odors. There were no differences among groups for absolute or intensity difference threshold or on simple 2-odor discrimination tests but both groups with bulbar lesions made more errors than controls on a relatively difficult odor-mixture task. The results demonstrate that removal of an area of the bulb identified as responsive to propionic acid is essentially without effect on sensitivity to that odor or ability to discriminate it from other odors.

Influence of training and experience on the perception of multicomponent odor mixtures.

This study examined whether a previously established (D. G. Laing & G. W. Francis, 1989) limited capacity to discriminate and identify the components of olfactory mixtures resulted from the participants' lack of familiarity with the task, training designed to optimize cognitive and perceptual performance, or professional experience in odor discrimination. The participants were a trained panel of 10 women (23-43 years old), and an expert panel of 8 male professional perfumers and flavorists (25-55 years old). The individual chemical stimuli were 7 common dissimilar odorants of equal moderate intensity. An air dilution olfactometer delivered a single odorant or a mixture containing up to 5 odorants. The results indicated that for both panels only 3 or 4 components of a complex mixture could be discriminated and identified and that this capacity could not be increased by training. Therefore, the limit may be imposed physiologically or by processing constraints.

The influence of flavor and color on drink identification by children and adults.

This study investigated how color and flavor influences drink identification by children and adults. The children ranged in age from 2 to 18 years of age. Each subject tasted four drinks that differed in color and flavor. Each drink had an atypical color-flavor pairing (e.g., brown-pineapple) or a typical pairing (e.g., brown-chocolate). After tasting each drink, the subject chose which of four flavor names identified the drink. For the atypical drinks, the selection of color-associated names (e.g., chocolate for a brown drink) decreased, and the selection of flavor-associated names increased with age from the preschoolers to the adults. For the typical drinks, the selection of the correct name was greater than 80% for all ages. These results suggest that drink identification becomes more influenced by flavor as children get older because of an increase in the ability of children to focus on flavor as their perceptual-attentional skills mature.