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At least 451 records · Page 25Linked to original sources

Retronasal and orthonasal olfactory function in relation to olfactory bulb volume in patients with posttraumatic loss of smell.

OBJECTIVE: The aims of this study were to evaluate olfactory function with orthonasal and retronasal testing in patients with posttraumatic olfactory loss and to investigate the relation between residual olfactory function and olfactory bulb (OB) volume. METHOD: A retrospective study of 25 patients with posttraumatic olfactory loss was performed. Orthonasal olfactory function was assessed with the Sniffin' Sticks test kit; retronasal olfactory function was assessed with intraorally applied odors. Magnetic resonance imaging was used to determine OB volume and cortical damage in the frontal and temporal areas. RESULTS: The main outcomes of the present study were the demonstration of a correlation between olfactory function and OB volume, which was more pronounced for retronasal than for orthonasal olfactory function; retronasal olfactory function was most affected in the patients with the most extensive cerebral damage and was least compromised in patients without such damage; OB volumes were smaller in patients with parosmia compared with those without; and the presence of parosmia was clearly associated with the presence of cerebral damage. CONCLUSION: The data confirm that OB volume is an indicator of olfactory function but, interestingly, in this study, it is largely determined by retronasal olfactory sensitivity. In addition, these results emphasize the role of higher cortical centers in olfactory function, and especially in parosmia, which may, at least in some cases, be related to lesions in the fronto-orbital and anterior temporal cortices. It would be of interest to investigate OB volume further in relation to the prognosis of the disorder.

Adult↗

Smells are no surer: rapid improvement in olfactory discrimination is not due to the acquisition of a learning set.

The claim that rats can demonstrate the 'primate-like' learning capacity of learning set formation when trained with olfactory cues, rather than visual or auditory cues, has generated considerable interest in recent years. In this study, the claim is evaluated in detail by using a series of experimental and control procedures to determine whether rats do indeed develop the abstract 'win-stay, lose-shift' strategy which underlies learning set formation in monkeys. We report here that although exposure to a series of novel olfactory discrimination problems gives rise to progressive improvement in the rate of learning, it is not a necessary condition for the development of that rapid learning. Furthermore, even rats which fail to display progressive improvement in olfactory reversal learning show rapid learning on novel olfactory discrimination problems. Each of these findings suggests that although olfactory learning may be rapid, learning set formation does not occur over a short series of problems.

Animals↗

The smell of cancer.

A middle aged man presented reluctantly to his General Practitioner with the complaint of offensive body odour and he was referred for a dermatological opinion. On examination a malignant looking ulcer emitting a foul odour was found in the site of his penis.

Anemia↗

Smell perception during early pregnancy: no evidence of an adaptive mechanism.

OBJECTIVE: It has been suggested that nausea and vomiting in pregnancy is an evolutionary adaptive mechanism to avoid the ingestion of potentially harmful foods. It has also been suggested that the mechanism that triggers nausea and vomiting in pregnancy may be olfaction and that olfactory senses are invoked to provide this protection. This study aimed to test this theory in a systematic design. DESIGN: Cross sectional study. SETTING: The antenatal department of a maternity hospital in the north of England. SAMPLE: Three groups of participants: pregnant women (n= 55), non-pregnant women (n= 42) and men (n= 48). METHODS: Sensitivity was tested towards the odours of six standard stimuli (half safe and half associated with potentially harmful compounds). MAIN OUTCOME MEASURES: Odour rating of likeness, strength and pleasantness. RESULTS: Pregnant women rated safe and odours with potentially harmful compounds differently but not more so than men or non-pregnant women. There was no evidence that pregnancy changed the olfactory processes from the non-pregnant state and only slight differences between pregnant women and men were recorded. CONCLUSIONS: There was no evidence that olfactory processes had undergone any adaptation during pregnancy. The ability to differentiate safe from potentially harmful compounds was common to all three groups studied.

Adaptation, Physiological↗

Detection of single and mixed VOCs by smell and by sensory irritation.

UNLABELLED: We have measured complete concentration-detection (i.e., psychometric or detectability) functions to study the olfactory and ocular/nasal chemesthetic (a term that includes sensory irritation) impact of VOCs presented singly and in various binary mixtures. Such functions provide considerably more information than that provided by measuring only a "threshold". The outcome for single VOCs confirmed the much higher absolute sensitivity of olfaction compared to chemesthesis, but also demonstrated that the detection of ocular and nasal sensory irritation increases as a function of vapor concentration at a much higher rate than that for the detection of odor. The outcome for the binary mixtures revealed that, for both olfaction and chemesthesis, complete additivity of detection of individual components held at relatively low levels of detectability but broke down at higher levels. The breakdown for odor detection, compared to that for sensory irritation detection, was, first, more extensive, and, second, dependent to a larger extent on the degree of structural and chemical similarity/dissimilarity between the mixed VOCs. PRACTICAL IMPLICATIONS: Concentration-detection functions for the chemesthetic and olfactory detectability of VOCs have shown that, even when nasal pungency and eye irritation begin to be evoked at concentrations orders of magnitude larger than those evoking odor, they sharply increase in detectability to become clearly noticeable. In contrast, odor detectability increases with concentration at a much lower rate. As a result, any fixed reduction (e.g., 10-times) in the concentration of a VOC will reduce detectability of sensory irritation much more dramatically than detectability of odor, within their respective ranges. Concentration-detection functions are particularly informative when employed to probe into the rules of dose- and response-additivity in mixtures. Our results for olfaction, and to a lesser extent for chemesthesis, indicate that additivity of detection of individual VOCs in mixtures is level-dependent: as detectability increases, the degree of additivity decreases. This suggests that a substantial improvement of perceived air quality could follow from control of just the few dominating chemosensory sources.

Adolescent↗