Olfaction, taste and trigeminal function are three distinct modalities. However, in daily life they are often activated concomitantly. In health and disease, it has been shown that in two of these senses, the trigeminal and olfactory senses, modification of one sense leads to changes in the other sense and vice versa. The objective of the study was to investigate whether and (if so) how, the third modality, taste, is influenced by olfactory impairment. We tested 210 subjects with normal (n = 107) or impaired (n = 103) olfactory function for their taste identification capacities. Validated tests were used for olfactory and gustatory testing (Sniffin' Sticks, Taste Strips). In an additional experiment, healthy volunteers underwent reversible olfactory cleft obstruction to investigate short-time changes of gustatory function after olfactory alteration. Mean gustatory identification (taste strip score) for the subjects with impaired olfaction was 19.4 +/- 0.6 points and 22.9 +/- 0.5 points for those with normal olfactory function (t = 4.6, p < 0.001). The frequencies of both, smell and taste impairments interacted significantly (Chi(2), F = 16.4, p < 0.001), and olfactory and gustatory function correlated (r (210) = 0.30, p < 0.001). Neither age nor olfactory impairment cause effects interfered with this olfactory-gustatory interaction. In contrast, after short-lasting induced olfactory decrease, gustatory function remained unchanged. The present study suggests that longstanding impaired olfactory function is associated with decreased gustatory function. These findings seem to extend previously described mutual chemosensory interactions also to smell and taste. It further raises the question whether chemical senses in general decrease mutually after acquired damage.

The study was designed to provide a topographical map of the sensitivity of the human nasal respiratory epithelium towards trigeminal chemosensory stimuli. As an electrophysiological measure of intranasal trigeminal activation at the level of the epithelium, we used the so-called negative mucosa potential (NMP), a measure that represents the sum of generator potentials of trigeminal receptor neurons after chemical stimulation. Sixty subjects participated (30 men and 30 women; mean age 23.5 years). Measurements were made in response to stimulation with menthol, CO(2), ethanol, and cinnamaldehyde, which are known to activate trigeminal receptors to various degrees. Recordings of the NMP were made from five intranasal sites: the anterior septum, the posterior septum, the tip of the middle turbinate, the tip of the lower turbinate, and the lateral side wall of the posterior nasal cavity. The recording electrode was positioned under endoscopic control. The largest NMP amplitudes were recorded at the anterior septum in response to stimulation with CO(2). Comparing all recording sites, significant differences were observed between responses at the posterior septum and the lateral side wall of the posterior nasal cavity in response to stimulation by ethanol, menthol, and CO(2). These findings suggest that the presence of topographical and chemosensory differences in the responsiveness of the nasal mucosa to irritants.

To investigate how nasally applied substances distribute in the nose depending on the form of application.

No abstract

Sex differences in olfactory sensitivity have been reported since the late 1800's with women typically outperforming men on tests of odor detection, discrimination or identification. It is not known whether women adapt differently than men to olfactory and trigeminal stimuli. Seventeen healthy volunteers participated (9 female, 8 male, mean age 22 years) in the study. As established by an odor identification test (UPSIT, score > or =38) all subjects had normal olfactory function. Event-related potentials (ERPs) were recorded in response to olfactory (25% v/v phenyl ethyl alcohol) and trigeminal (44% v/v CO(2)) stimuli using a computer controlled olfactometer (flow 8 L/min; stimulus duration 200 ms). Stimuli were applied at four intervals (5, 10, 20, and 60 s). Amplitudes and latencies of ERP peaks P1, N1, and P2 were measured. Stimulus intensity also rated using visual analogue scales subjects. When compared to phenyl ethyl alcohol, the slightly more intense CO(2) produced larger amplitudes and shorter latencies. Both, ratings and ERP amplitudes P2 decreased with decreasing interval between stimuli. Responses to the trigeminal and olfactory stimuli changed similarly in relation to repetitive stimulation. Women had larger ERP amplitudes P2. No sex-related difference for ratings and ERP in relation to repeated stimulation amplitudes was observed. Although women exhibit larger ERP amplitudes to chemosensory stimuli compared to men, the present data indicate on both psychophysical and electrophysiological levels that there is no major difference between young, healthy men and women in relation to short-term adaptation to suprathreshold chemosensory stimulation.