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PubMed2005

[Psychophysiological basis of smells].

There has been an increase in the use of psychophysiological techniques, especially event-related potentials (ERPs) to evaluate the effects of odor on the central nervous system. In the study of ERPs related to odor, there are two main methods of the odor presentation: (1) to investigate the olfactory ERP (OERP) or chemosensory ERP (CSERP), that is to calculate electrophysiological responses to odor stimulation as a trigger; (2) to compare ERP of mental functioning during the odor exposed condition with that of no odor exposure. The amplitude of contingent negative variation (CNV) varies with the odorant being present, when the odor is presented as a trigger and when it is administrated during a task. It is suggested that CNV changes depend on not only the odorant but the anticipation, expectation and emotion of the subject. The latency of the N1 component becomes shorter with increasing concentrations of odors. The N1 amplitude does not depend on the odor concentration while the amplitude of the auditory N1 strongly depends on the stimulus intensity. There is only one report that the olfactory mismatch negativity (MMN) is present in the CSERP. On the other hand, auditory MMN is not affected by odor administration. In relation to the P3 component, rare odors evoked a larger amplitude in contrast to frequent odors, as well as P3 evoked by other modalities. These ERP studies with odors are expected to be applied to such clinical settings as the differentiation between the anosmic patients and normosmic persons, the functional evaluation of patients with brain tumors, the earlier detection of dementia, and the objective evaluation of aromatherapy.

Aromatherapy↗
PubMedDate not supplied

Initial events in stimulation of taste and smell receptor cells.

Analysis of the initial interactions of chemicals with olfactory and taste receptor cells is complicated by problems in controlling stimulus presentation. These interactions arise from chemicals diffusing through an unstirred layer to reach the cell surfaces and, in the case of olfaction, partitioning into mucus from air. In many instances, the odorants are metabolized to products that may be stimulants. In such cases, the analysis is further complicated by uncertainty about which chemical species actually stimulate. Stimulation of chemoreceptors can be thought of as originating from specific and nonspecific interactions of stimuli with the cells. Specific interactions involve receptor proteins in or on the cell membranes. These interactions are probably important in initiating sweet taste but not in detecting salty or sour stimuli. There are many reported preparations including putative olfactory receptor proteins, and evidence exists that the proteins comprise a structurally similar class. In some, the proteins are demonstrated to have olfactory function, but blocking their interaction with odorants only partially inhibits olfactory responses. The remainder of the responses presumably occur by general irritant effects of odorants and their metabolites.

Animals↗
PubMed1991

[Development of the sense of smell, a review].

The pre- and postnatal development of human olfaction is described. Data from animal experiments a partially reviewed as a base for understanding of the results of olfactory testing of babies and children. In rat fetuses the vomero-nasal-organ is used as detector of molecules in the amnion fluid. The perinatal aeration of the nasal cavity allows the adequate stimulation of the olfactory epithelium. The early postnatal olfaction is a brainstem function; later the olfactory cortical area are used for the discrimination between odorants. There are only a few investigations about the olfactory function in childhood, so that the testing of olfaction for detecting abnormal brain developments is just in the beginning.

Animals↗