Pamela M. Eller

Fast and accurate measurement of taste and smell thresholds using a maximum-likelihood adaptive staircase procedure.

This paper evaluates the use of a maximum-likelihood adaptive staircase psychophysical procedure (ML-PEST), originally developed in vision and audition, for measuring detection thresholds in gustation and olfaction. The basis for the psychophysical measurement of thresholds with the ML-PEST procedure is developed. Then, two experiments and four simulations are reported. In the first experiment, ML-PEST was compared with the Wetherill and Levitt up-down staircase method and with the Cain ascending method of limits in the measurement of butyl alcohol thresholds. The four Monte Carlo simulations compared the three psychophysical procedures. In the second experiment, the test-retest reliability of ML-PEST for measuring NaCl and butyl alcohol thresholds was assessed. The results indicate that the ML-PEST method gives reliable and precise threshold measurements. Its ability to detect malingerers shows considerable promise. It is recommended for use in clinical testing.

Postviral Olfactory Dysfunction

Seventeen patients with varying degrees of olfactory dysfunction were studied at the Rocky Mountain Taste and Smell Center in Denver, Colorado. Detailed chemosensory testing was carried out, followed by biopsy of the olfactory mucosa. Ultrastructural study of the biopsies revealed near-complete degeneration of the ciliated olfactory receptors of anosmic patients and reduced populations of ciliated olfactory receptors in the hyposmic patients. Based upon these observations, it is postulated that upper respiratory infection can produce a spectrum of histopathologic change in the olfactory epithelium which can be correlated with afunctional deficit. The clinical implications of these observations are discussed.

Calbindin-like immunoreactivity in two peripheral chemosensory tissues of the rat : taste buds and the vomeronasal organ

In the rat, calbindin-like immunoreactivity was observed at both the light and electron microscopic levels within the chemoreceptor neurons of the vomeronasal organ (VNO) and both intragemmal cells and associated nerve fibers of the circumvallate taste buds. All VNO neurons were immunoreactive. Only a subset of intragemmal taste cells was immunoreactive; associated immunoreactive nerve fibers were apposed to both labeled and unlabeled cells but no synaptic contacts were observed.

Steroid-Dependent Anosmia

In steroid-dependent anosmia (nasal polyps, inhalant allergy, anosmia), high doses of steroids will temporarily restore the sense of smell, a diagnostic test. Appropriate surgery can then be carried out, followed by low-dose, long-term steroid therapy to maintain the sense of smell. Olfactory biopsy specimens taken during the course of evaluation and treatment show electron-optically normal olfactory receptors, meaning that the probable pathogenesis of the sensory deficit is an obstruction, mechanical and possibly biochemical. Two cases of steroid-dependent anosmia are presented to detail a fully reversible anosmia using state-of-the-art techniques.

Ultrastructural Changes of the Olfactory Epithelium in Alzheimer's Disease

Recent studies have demonstrated an association between abnormalities in the sense of smell and Alzheimers disease (AD). In our laboratory we have shown that olfactory dysfunction is accompanied by histopathological changes in the olfactory epithelium. These findings led us to believe that there were changes in the olfactory epithelium in AD that resulted in altered olfactory function. In the present study we have done biopsies of tissue from 12 patients who have been screened thoroughly and diagnosed with probable AD. Olfactory epithelium from 10 of these patients has been examined at the electron microscopic level. The overall appearance of the epithelium is altered from that seen in normosmic, age-matched controls. The ultrastructural appearance of olfactory receptor cells and support cells is disrupted. In addition, a crystallinelike material has been observed over the surface of the olfactory epithelium in six patients. This material was not observed in the respiratory epithelium of the same patients and has not been seen by us in any other pathological or normal tissues we have examined. The overall appearance of the olfactory epithelium in these probable AD patients seems to be unique when compared with other pathological states examined so far. The present study suggests that olfactory epithelium biopsy may be useful in the early detection of AD.