One mechanism possibly leading to olfactory dysfunction is a compromise in the ability to sniff or inhale air through the nose. Obviously, if odorant molecules cannot reach the olfactory region, there can be no olfactory perception. Furthermore, the extent to which the airflow towards the olfactory mucosa is altered may be reflected in the extent to which olfactory perception is compromised. Central to normal airflow through the nose is the sniffing strategy a subject uses while exploring the odorous environment. In this regard, perhaps one of the salient features of the olfactory system is the control the user exerts over his/her own sniffing behavior and consequently over his/her own olfactory information. Therefore, the long-term objective for this project is to quantitatively describe sniffing behavior and examine its importance in shaping the perception and discrimination of odors in animal models and humans. To this end, we will use a pneumotachometer to systematically study the sniffing strategies of animal models as well as humans in order to identify the significant features of sniffing behavior and how there features may differ for different olfactory tasks. Using standard operant techniques and a discrete-trials go-no-go successive discrimination paradigm, the sniffing strategies of rat and dogs performing an odor detection task, odor intensity discrimination, or a two-odor discrimination task will be examined. Likewise, the sniffing strategies of patient populations and normal controls will be examined while the subjects perform an odor detection task, magnitude estimation determination, or confusion matrix task. With the information provided by the animal behavioral studies we will examine the role of sniffing on the mode of odorant molecule dispersal in the nasal airways of the animal models under conditions duplicating the subject's own sniffing behavior. To accomplish this we will use radioactively-labelled odorants and an artificial sniff generator which duplicates the sniffing parameters actually produced by the behaving animal. In addition, we will use the behavioral information in conjunction with the artificial sniff generator to examine the role of sniffing on the processing of olfactory information. In this regard, systematic variations in the parameters of sniffing will be related to the electrophysiologically recorded activity from the olfactory nerves of rats.
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