Odorant quality perception: a metric individual differences approach.

Perceptual spaces, in which similar stimuli are located close to each other and dissimilar stimuli are located far apart, have aided in the understanding of the physiological and psychological bases for sensory quality coding. Differences in perception between individuals should be reflected by differences in the spatial relationships between stimuli. If the dimensionality of the perceptual space is small (e.g., color space), individual differences that reflect specific pathologies are readily apparent from visual inspection. On the other hand, if the dimensionality of the perceptual space is large (as is proposed for odor space), visual inspection alone may not reveal individual differences in quality perception. The present work presents an information-theory-based method for quantifying individual differences in quality perception from perceptual confusion matrices. The ability of this method to quantify individual differences in quality perception is shown in a hypothetical example of specific anosmia. Finally, the method is applied to the examination of intrasubject consistency of odorant quality perception.

Olfactory dysfunction in diabetes mellitus.

Olfactory dysfunction has been reported in individuals with diabetes mellitus, but the etiology is unknown. Diabetes is often complicated by serious medical conditions which could be related to the development of decreased olfactory ability. Overall, our 111 subjects with diabetes showed deficiencies in their ability to identify odorants measured with the Odorant Confusion Matrix (mean = 67.8% correct). The presence of macrovascular disease was found to be associated with olfactory dysfunction. Glycemic control as well as the type and duration of diabetes were not related to olfactory ability. Also, there was no distinct association with the presence of neuropathy, retinopathy, nephropathy, hypertension, or impotence. Consistent with previous studies utilizing measures of odorant identification, performance decreased with increased age, females were somewhat superior to males, and smoking had a deleterious effect. Other nondiabetes-related medical conditions and medications had no apparent effect on the olfactory ability of our subjects. These results suggest that the sequelae associated with macrovascular disease, such as perhaps, ischemia, to the olfactory area, impact negatively on olfactory ability.

Olfactory performance during childhood. I. Development of an odorant identification test for children.

Because there has been no suitable diagnostic instrument for evaluation of olfaction in children, we designed an odorant identification test for that purpose. We screened 40 microencapsulated odorants ("scratch 'n' sniff" cards) by randomly grouping them into 40 overlapping sets of five odorants each. Forty-one children, 4 and 5 years of age, tried to identify each test odorant, selecting their responses from among five photographs depicting the substances in the set of odorants. We used the results to select a subset of five odorants (baby powder, bubble gum, candy cane, fish, and orange). To determine how well these odorants could be identified by normal children, we tested another 134 subjects, 3 1/2 to 13 years of age. For children 3 1/2 years to 5 years 4 months of age, the mean (+/- SEM) percentage of correct responses increased from 66% +/- 8% to 92% +/- 2%. Thereafter the mean percentage of correct responses remained at a plateau of about 90%. The 10th percentile for the percentage of correct responses tended to be higher for girls than for boys throughout childhood. We concluded that this set of five odorants can be correctly identified by most normal children 5 years of age or older. The performances of three older subjects with Kallmann syndrome were all subnormal, but the overall efficacy of the test for evaluating children with olfactory deficits needs to be determined.

Successful treatment of phantosmia with preservation of olfaction.

A 26-year-old woman had an 8-year history of phantosmia in her left nostril. The phantosmia could be eliminated by nostril occlusion or cocainization of the olfactory epithelium on the involved side. Because her symptoms and testing suggested a peripheral problem, a full-thickness "plug" of olfactory epithelium from under the cribriform plate (including all the fila olfactoria) was excised. At 5 weeks postoperatively, the phantosmia was completely gone, and her olfactory ability had returned to preoperative levels. Either the removal of abnormal peripheral olfactory neurons from the nose or the interruption of incoming signals to the olfactory bulb eliminated the phantosmia. This form of therapy for phantosmia offers an alternative to more radical procedures such as olfactory bulbectomy and may offer a significant sparing of olfactory ability.

Fish-odor syndrome presenting as dysosmia.

We describe a patient who had perceived an unpleasant odor or taste for at least 20 years. Several other physicians had unsuccessfully treated her for infections, mucus membrane dryness and inflammation, chronic tonsillitis, and psychiatric disorders. Her workup at the State University of New York Health Science Center at Syracuse Olfactory Referral Center included a thorough history, examinations (including endoscopic studies of her nose, pharynx, and lungs), roentgenograms, taste testing, olfactory testing, and selective anesthesia of her chemosensory areas. The perception occurred only during exhalation, and appeared to be binasal. These findings, together with her morning mucus sample having a strong fishlike odor, prompted us to suspect a metabolic problem. Further testing at the Monell-Jefferson Chemosensory Clinical Research Center, Philadelphia, Pa, confirmed that she had trimethylaminuria. It is important to consider this and other treatable conditions when evaluating individuals with olfactory complaints.

Characterization of olfactory dysfunction.

Management of dysosmic patients frequently is hampered by an incomplete description of their chief complaint and sometimes inadequate qualitative analysis of their symptoms. Qualitative analysis of olfactory dysfunction by an Odorant Confusion Matrix helps to characterize more fully sense of smell in the dysosmic patient. It is well grounded in psychophysical theory, thereby permitting physiological inferences about specific neural dysfunctions. The quantitative measure derived from the matrix correlates well with another quantitative measure of olfactory ability, the Smell identification Test, and provides the opportunity for valid comparisons among and within patients. Examination of illustrative case reports demonstrates that the qualitative features of the Odorant Confusion Matrix offer additional insights to support etiologic diagnoses of disturbances in sense of smell.

The initial evaluation of dysosmia.

Patients with disturbances in their sense of smell often represent a bewildering array of alternative diagnoses. The existing knowledge of olfactory disorders has been schematized into a systematic history approach toward the development of a differential diagnosis for dysosmic patients. Its components should elicit essential elements of the history which, according to the literature, have been associated with dysosmia. The ability to update the details of specific components permits it to be adapted to the needs of the individual practitioner.

Olfactory dysfunction in humans with deficient guanine nucleotide-binding protein.

The guanine nucleotide-binding stimulatory protein (Gs) couples hormone-receptor interaction to the activation of adenylate cyclase and the generation of cyclic AMP. Studies using frog neuroepithelium indicate that the sense of smell is mediated by a Gs-adenylate cyclase system, and this prompted us to test olfaction in the only known model of Gs deficiency in the animal kingdom, Gs-deficient (type 1a) pseudohypoparathyroidism (PHP), which occurs in humans. Such patients are resistant to the cAMP-mediated actions of several hormones. (Although Henkin has reported disturbances in the sense of smell in six patients with PHP, currently available biochemical measurements such as the cAMP response to parathyroid hormone (PTH) and determination of Gs activity were not reported and olfactory testing was limited.) In the present study, we found that all Gs-deficient patients had impaired olfaction when compared with PHP patients who had normal Gs activity (type 1b PHP, in which patients are resistant only to the action of PTH in the kidney). This is the first evidence of human olfactory impairment which can be related to Gs deficiency and suggests that Gs-deficient PHP patients may be resistant to cAMP-mediated actions in other non-endocrine systems.

The influence of probe-tone parameters on the shape of psychophysical tuning curves in normal-hearing listeners.

Psychophysical tuning curves have become increasingly important in furthering the interpretation of traditional masking data. Although a substantial amount of relatively new information is available on psychophysical tuning curves, the analysis and interpretation of this information are difficult because of the lack of consistency among the probe-tone parameters used. This study investigated the shape of psychophysical tuning curves under simultaneous masking as a function of three frequencies--500, 1000, and 4000 Hz; three levels--5, 20, and 40 dB SL; and two durations--10 msec and 200 msec, of the probe tones. The results indicate that the general shape of psychophysical tuning curves is consistent throughout the 18 combinations of parameter values studied. Irregularities such as notches and CF shifts, inconsistently noted in previous investigations, were observed in the shape of psychophysical tuning curves. However, they were shown to depend on unique combinations of probe-tone parameters. These results are compared to previous investigations of simultaneous-masking psychophysical tuning curves with respect to the specific effects of probe-tone parameter values on the shape of the curves. Irregularities in the shape of psychophysical tuning curves are discussed in relation to aural combination tones and other nonlinearities.

Brief-tone audiometry in pseudohypacusis.

Brief-tone audiometry was administered to two groups of listeners. The first group consisted of five sophisticated subjects with normal hearing, who were tested under normal and simulated hearing-loss conditions. The second group consisted of five patients with true pseudohypacusis. Results under simulated and true pseudohypacusic conditions were similar, but were different from those obtained from the normal listeners under normal conditions, which further extends the diagnostic value of brief-tone audiometry.

Auditory temporal summation in presbycusis and noise exposure.

Threshold-duration functions were obtained at 250, 1000, and 4999 Hz by Brief-Tone Békésy Audiometry. Results for an older group (51-57 yrs.) with no otological abnormalities showed the presence of depressed threshold-duration functions with a decreased constant of temporal summation when compared to a young normative group. The effect is frequency dependent and is most pronounced at 4000 Hz. The older group, divided into noise exposed and non-noise exposed subsamples, showed identical threshold-duration functions and resembled those for a young noise exposed group. Auditory temporal summation appears to be affected by the neuorphysiological disturbances of presbycusis and at least from 51 to 57 years is independent of noise exposure.