Anthony L Jinks

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.

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.

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.

Rapid quantitative assessment of fungiform papillae density in the human tongue

Fungiform papillae density, which can be used in a variety of circumstances as an indicator of taste function [L.M. Bartoshuk, V.B. Duffy, I.J. Miller, PTC/PROP tasting: anatomy, psychophysics and sex effects, Physiol. Behav. 56 (1994) 1165-1171; I.J. Miller, F.E. Reedy, Variation in human taste bud density and taste intensity perception, Physiol. Behav. 47 (1990) 1213-1219; J.R. Zuniga, N. Chen, C.L. Phillips, Chemosensory and somatosensory regeneration after lingual nerve repair in humans, J. Oral Maxillofac. Surg. 55 (1997) 2-13], was measured on the dorsal surface of the anterior tongue of living humans using a digital camera and a videomicroscope. Both procedures provided similar results, with the camera providing a more rapid, portable and flexible imaging procedure. Subsequently, the camera was successfully used to identify small regions of the anterior tongue which provide reliable measures of fungiform papillae density that correlate highly with the total number of fungiform papillae on the anterior tongue.

The limited capacity of humans to identify the components of taste mixtures and taste-odour mixtures

The capacity of humans to identify the components of taste mixtures and odour – taste mixtures was investigated in two experiments. Subjects were trained to identify the components presented alone and to use a ‘yes/no’ procedure to identify them in mixtures. All stimuli were presented with a retronasal (by mouth) technique. A maximum of three tastants were identified in both types of mixtures, only one tastant was identified in five-component taste mixtures, and no component was identified in four-component odour – taste mixtures. Importantly, in no instance was the olfactory stimulus identified in any mixture with tastes, including binary mixtures. Loss of identity of the odorant in binary and ternary mixtures may have been due to suppression as a consequence of temporal processing, or to the absence of an association between the odorant and tastants that had established an identifiable percept. In contrast, poor identification of the components of the quaternary odour – taste mixture and quinternary taste mixture is attributed to the limited capacity of working memory. Overall, the poorer ability to identify components in odour–taste mixtures than in taste mixtures indicates that interactions occurred between the two senses, challenging the proposal that odours and tastes are processed independently when present in complex chemosensory stimuli.

A quantitative study of fungiform papillae and taste pore density in adults and children

Male children (8-9 years) are reported to have a higher sensitivity than male adults to the sweet tastant sucrose when small regions of the anterior tongue are stimulated. The present study investigated the hypothesis that the higher sensitivity was due to a greater density of fungiform papillae and taste pores (buds), since it has been reported in adults that increased densities of these two structures correlates with increased taste suprathreshold sensitivity [Physiol. Behav. 47 (1990) 1213]. Quantitative measures of the number and size of papillae and pores in two areas of the tongue that had been shown to have a higher sensitivity for sucrose were achieved in 20 male children 8-9 years of age and 20 adults 18-30 years of age, using videomicroscopy and NIH Image software. Customized templates and a red food dye were used to define the equivalent tongue locations across the 40 subjects and taste pores were stained with methylene blue. Children were found to have substantially smaller papillae than adults but significantly higher papilla densities in both areas. Similar numbers of taste pores per papilla were found for both groups, resulting in children having much higher taste pore densities in each area than adults. Other differences included smaller taste pore diameters in children compared to adults, and the papillae tended to be rounder in children. Overall, the results support the hypothesis that the higher densities of fungiform papillae and taste pores in children underlie their greater sensitivity for sucrose in the two areas. In addition, the anatomical differences between adults and children indicate the sense of taste is in a state of development during mid-childhood.

Flavour perception mechanisms

Perception of the flavour of foods is a complex process that involves the senses of smell and taste, and chemesthesis (the common chemical sense; also called pungency or irritation). Each sense contributes special characteristics to a flavour through its ability to interact with different types of chemical stimuli, or through neural interactions that may modulate the responses of the other senses. In this overview, we describe the major features of flavour perception in the context of the production of flavour during the eating process, the mechanisms of flavour reception and perception, the interactions of the chemical senses and, briefly, the influence or role of flavour in food acceptance and nutrient intake, and the possibility of replacing humans with instruments for the objective measurement of flavour.

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.

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.

Taste development: differential growth rates of tongue regions in humans

There is a paucity of information about the anatomical and functional development of the human gustatory system. Although the anatomical development of the taste-sensitive fungiform, circumvallate and foliate papillae in the respective anterior, posterior and latero-posterior regions of the dorsal surface of the tongue has been well documented in the fetus, there is limited information about how these regions grow and when they exhibit adult function. The present study is concerned with determining when the growth of one of these taste-sensitive regions becomes adult in size, namely, the anterior region, and how this growth compares with that of the remaining posterior region. Two-hundred and thirty-two living subjects aged between 4 and 32 years participated. Following the identification and marking of a series of landmarks on the dorsal surface of the tongue with blue food dye, five measurements of the width and length of various parts of the tongue allowed calculation of the growth of the anterior and posterior regions. The results indicate that the fungiform papillae-rich anterior region attains adult-size by 8-10 years of age whilst the posterior region continues to grow until 15-16 years. Interestingly, this early development is not matched by achievement of adult function [Dev. Brain Res. 82 (1994) 286] or adult size papillae or taste pores [Dev. Brain Res., submitted]. Finally, the findings of the present study will allow studies of the development of taste function in humans to be conducted using equivalent tongue areas in subjects of different ages.