James M. Weiffenbach

Genetic variation and inferences about perceived taste intensity in mice and men.

The study of genetic variation in taste produces parallels between mice and men. In mice, genetic variation across strains has been documented with psychophysical and anatomical measures as well as with recordings from whole nerves. In humans, the variation has been documented with psychophysical and anatomical measures. Whole-nerve recordings from animals and psychophysical ratings of perceived intensities from human subjects have a similar logical limitation: absolute comparisons across individuals require a standard stimulus that can be assumed equally intense to all. Comparisons across whole-nerve recordings are aided by single-fiber recordings. Comparisons across psychophysical ratings of perceived intensity have been aided by recent advances in methodology; these advances now reveal that the magnitude of genetic variation in human subjects is larger than previously suspected. In females, hormones further contribute to variation in taste. There is evidence that the ability to taste (particularly bitter) cycles with hormones in women of child-bearing age, rises to a maximum early in pregnancy and declines after menopause. Taste affects food preferences, which in turn affect dietary behavior and thus disease risks. Valid assessment of taste variation now permits measurement of the impact of taste variation on health. Advances in psychophysical methodology were essential to understanding genetic variation in taste. In turn, the association of perceived taste intensities with tongue anatomy now provides a new tool for psychophysics. The ability of a psychophysical scale to provide across-subject comparisons can be assessed through its ability to show the fungiform papillae density-taste association.

Association Between 6-n-Propylthiouracil (PROP) Bitterness and Colonic Neoplasms

Inadequate vegetable intake appears to increase colon cancer risk. Since genetic variation in taste influences vegetable preference, we tested associations between bitterness of 6-n-propylthiouracil (PROP), a measure of taste genetics, and number of colonic polyps, a measure of colon cancer risk, in 251 men who underwent screening lower endoscopy. Patients used the general Labeled Magnitude Scale to rate bitterness of 1.6 mg PROP delivered via filter paper. A subset of 86 patients reported weekly vegetable intakes, excluding salad or potatoes. PROP bitterness correlated significantly with polyp number, an effect separate from age-associated increases in polyp number. The PROP–polyp relationship was strongest in men over 66 years, and older men with polyps were most likely to be overweight or obese. In the subset reporting vegetable intake, men who tasted PROP as more bitter consumed fewer vegetables. These preliminary findings suggest that taste genetics may influence colon cancer risk, possibly through intake of vegetables.

Taste intensity performance in patients irradiated to the head and neck

Decrements in taste-detection thresholds during radiotherapy and subsequent recovery in the months after therapy are well documented. However, few studies have explored suprathreshold taste intensity perception in radiation patients. This cross-sectional study compared taste function in 15 men postradiation with a group of 23 healthy, nonirradiated male volunteers. A direct-scaling procedure was used to assess taste intensity perception of the four basic taste qualities. Patients performed nearly as well as control subjects on objective measures of suprathreshold functioning. Postradiation intensity judgments of salty (sodium chloride), sweet (sucrose), and bitter (quinine sulfate) solutions were not significantly reduced. Subtle, age-related taste impairments were identified for sour perception (citric acid) postradiotherapy. Younger patients judged citric acid to be more intense than did age-appropriate control subjects, whereas older patients judged it to be less intense. Moreover, younger patients were likely to be midly dysgeusic, whereas older patients appeared to be hypogeusic for citric acid. This study provides evidence for near normal suprathreshold taste intensity perception in patients who have received head and neck irradiation.

Clinical examination of motor and sensory functions of the adult oral cavity

Alterations in oral motor and sensory performance are common. A traditional head and neck examination, however, does not fully assess these functions of the oral-facial region. This article presents an examination that emphasizes the clinical evaluation of oral motor and oral sensory abilities. These procedures should be considered as an addition to a routine assessment of the head and neck. An uncomplicated summary severity rating scale was developed to express the results of this examination. Two case reports demonstrate the utility of the examination in diagnosis and management of patients with oral complaints.

Optimizing sensation and perception in older adults

Age-related differences in adult sensory and perceptual function are reviewed for vision, hearing, taste and smell, using laboratory-based research as well as clinical, survey and field studies. In each area, ergonomic interventions aimed at optimizing the performance of older adults are explored. These optimization strategies include modifications to the environment, person and task design. Future research needs are also identified and discussed.

Assessment of Chemosensory Functioning in Aging: Subjective and Objective Procedures

Assessments of human sensory and perceptual functioning are meaningfully classified as either subjective or objective. Both subjective and objective measures have been employed in studies of age-related changes in chemosensory functioning. Subjective and objective assessments proceed from different philosophic assumptions, provide different types of information, and play different roles in understanding age-related change. Subjective assessment exploits each persons unique access to the functioning of his or her own sensory apparatus. It assumes that subjects can and will give an accurate account of their sensory experience and is distinguished by the attempt to directly communicate private experience. Objective assessment strategies circumvent the practical and philosophical problems of verifying and communicating private experience. Objective measures assume that sensory function is reflected in the subjects performance of tasks that require perception of the relevant sensory information. Subjective measures are primarily descriptive. They can be used to characterize chemosensory experience and may reveal the fullness and drama of age differences. Objective measures, while they may fail to capture the richness of perceptual experience, are directly relevant to the investigation of the underlying mechanisms. Thus, subjective measures serve to direct attention to the issues and phenomena of perceptual change in aging whereas objective measures are most useful for specifying and evaluating candidate mechanisms by which these changes might be generated.

Taste-quality recognition and forced-choice response

The Collings (1974) procedure for measuring taste-quality recognition thresholds controls adequately for bias caused by variation in the willingness of subjects to report perceiving a taste quality. However, it fails to control for bias due to the preference of subjects for one response over another. In the present study, preferential selection among the response alternatives was reflected in the disproportionate occurrence of the four taste-quality names among incorrect responses. Response preferences were idiosyncratic and grew stronger with repeated testing. They were not eliminated by informing subjects of the correctness of their responses. Use of this procedure for measuring recognition thresholds is discouraged.

Human Sensory Function for Taste Is Robust Across the Adult Life-Span

The persistent belief that taste function declines with age encourages the study of the relation of human taste to aging. Differences in taste function between younger and older individuals are inherently as interesting as those between individuals of different sexes or who differ with respect to some other characteristic. Age differences are, however, of particular personal relevance because all of us are growing older. To specify age differences in sensory function for taste requires resolution of three issues. One is the distinction between age-related and nonage-related differences between older and younger people. Another is the distinction between differences in experience or performance that reflect sensory differences and those that do not. Finally, the tyranny of the idea that sensory declines with aging are universal and inevitable must be addressed.

Touch and taste in the mouth: Presence and character of sapid solutions

Complex dynamic properties of a bolus in the mouth are specified by touch. Cooperation between touch and taste may help to specify the character of the bolus. The role of touch in specifying the presence of the oral bolus, in contrast to its characteristics, remains a theoretical and experimental challenge.

Quantitative Assessment of Oral Tactile Sensitivity in Pre-term and Term Neonates, and Comparison with Adults

The tongues of 34 infants between 31 and 40 weeks estimated gestational age were stimulated with filament esthesiometers. Stereotyped ipsilateral movements of the tongue were elicited in all infants. An assessment of tactile sensitivity based on this reflex is minimally affected by infant activity state and habituation to repeated stimulation. Small pre‐term infants (31 to 35 weeks gestation) and infants born near term (37 to 40 weeks gestation) were more sensitive to tactile stimulation than an intermediate group (35 to 37 weeks gestation). In infants followed longitudinally, a transient decrement in sensitivity occurred at two weeks postnatal age. The tactile sensitivity in 12 adults (as measured by their correct reports of stimulus location) was far greater than the sensitivity of the infants.