Biomedical subjects

J Frasnelli

Publications and source records attributed to J Frasnelli.

8 recordsLinked to original sources

PubMed2007

The neural representation of odor is modulated by the presence of a trigeminal stimulus during odor encoding.

OBJECTIVES: Odor perception does not simply consist in hierarchical processing from transduction to a single "true" cerebral representation. Odor sensation may be modulated by available sensory information during encoding. The present study set out to examine whether the presence of a pure trigeminal stimulus during odor encoding may modulate odor perception at both behavioral and cortical levels. METHODS: Participants were tested in a 2-session within-subject design: first, an odor encoding session included a delay conditioning procedure in which relatively selective olfactory stimulants (phenyl ethyl alcohol or vanillin, Conditioned Stimulus+, CS+) were presented either with a pulse of CO(2) (Unconditioned Stimulus, US), or alone (Conditioned Stimulus-, CS-); then, in the second session, both pure odorants (CS+ and CS-) were presented alone. During this second session, olfactory event-related potentials were simultaneously recorded and analyzed at different electrode sites including Cz and Pz (sites known to have maximal amplitudes for trigeminal and olfactory stimuli, respectively). After each trial, subjects were asked to rate odor intensity and hedonics. RESULTS: The results showed that CS+ intensity ratings increased in 8 subjects and decreased in 6. Cortically, a group effect was observed for P2 amplitude, which increased in the "CS+ intensity increase" group vs. the "CS+ intensity decrease" group at Cz (p<0.05) but not at Pz (p>0.05). CONCLUSIONS: This result suggests that the presence of a pure trigeminal stimulus (CO(2)) during odor encoding alters the neural representation of a pure odor. SIGNIFICANCE: The neural representation of odors comprises not only the odor itself but also contextual information (trigeminal in the present case) presented during encoding.

Adult↗

PubMed2006

Chemosensory specific reduction of trigeminal sensitivity in subjects with olfactory dysfunction.

Humans with olfactory loss have been found to exhibit a decreased sensitivity of the chemosensory trigeminal system. It is not clear, whether the reduced trigeminal sensitivity is restricted to the chemosensitive properties of the trigeminal nerve, or whether it reflects a general decrease of trigeminal sensitivity which is also found for cutaneous afferents. To investigate the relationship between cutaneous somatosensory and intranasal chemosensory trigeminal sensitivity, 91 subjects were investigated. Forty-five of them were considered healthy controls, whereas 46 subjects had olfactory dysfunction. Subjects with olfactory dysfunction were found to have higher thresholds for CO2 than controls indicating lower trigeminal chemosensory sensitivity in subjects with olfactory dysfunction. Both etiology and degree of olfactory dysfunction appeared to have an impact on CO2 thresholds. In contrast, no such differences were found with regard to detection thresholds for electrical cutaneous stimulation. These results indicate that the decrease of trigeminal sensitivity in subjects with olfactory dysfunction is specific for chemosensory sensations.

Adult↗

PubMed2006

Subjects with congenital anosmia have larger peripheral but similar central trigeminal responses.

Most odorants not only stimulate olfactory receptor neurons but also activate the intranasal trigeminal nerve. The simultaneous activation of the olfactory and the trigeminal system leads to an interaction in the brain. Therefore, assessment of the trigeminal impact of odorants may be difficult in subjects with a normal sense of smell. To obtain a deeper insight into both, mechanisms of changes in trigeminal sensitivity in anosmic patients and interactions between the olfactory/trigeminal systems in healthy subjects, 21 patients with isolated congenital anosmia (ICA) were investigated in this series of explorative, hypothesis-generating experiments and compared with 35 healthy controls. Trigeminal sensitivity was measured by psychophysical (lateralization task, intensity ratings) and electrophysiological (trigeminal event-related potential, negative mucosal potential) means. ICA patients were found to have higher peripheral activation than controls. On central levels, however, similar responsiveness to trigeminal stimuli was found in ICA patients when compared with healthy subjects. The results of the study are discussed by proposing a model of mixed sensory adaptation/compensation in the interactions between olfactory and the trigeminal system.

Adolescent↗

PubMed2006

Euosmia: a rare form of parosmia.

The nature of qualitative olfactory disorders such as phantosmia and parosmia is a matter of debate. Parosmia and phantosmia mainly occur in combination with post-traumatic or post-infectious olfactory loss. Rare causes of these disorders such as brain tumors, side-effects of drugs, paraneoplastic syndromes, psychiatric disorders or intracerebral haemorrhage have been reported. Parosmias are distorted sensations of smell elicited by an odor, whereas phantosmias persist permanently or occur without the presence of an odor source. Phantosmias differ widely in terms of their nature. In contrast, parosmias always seem to be unpleasant. We report the case of a female with post-infectious hyposmia who reported a pleasant parosmia to selected odorants. We have called this rare clinical presentation euosmia.

Antioxidants↗

PubMed2006

Post-infectious olfactory dysfunction exhibits a seasonal pattern.

HYPOTHESIS: We investigated whether olfactory dysfunction following infections of the upper respiratory tract (post-URTI) has an incidence matching the seasonality of URTIs. STUDY DESIGN: Retrospective study. METHODS: In total, 457 patients (126 male, 331 female) with post-URTI olfactory loss were examined during a 6-year-period (1999-2004). Their records were assessed for age, sex, and time of onset of the disease. The severity of olfactory dysfunction was assessed using the "Sniffin' Sticks" (odour threshold, odour discrimination, and odour identification). RESULTS: Incidence of post-URTI olfactory dysfunction exhibited seasonal fluctuations with deviations from the winter seasonality of URTIs. The overall incidence of the disease differed significantly between months. March (12.7%) and May (12.6%) were the months with the highest incidence of the disease throughout the year. The lowest incidence was observed in September (5.6%). Significant differences were found between these months and months with a high incidence of URTIs. DISCUSSION: The peak incidence of post-URTI olfactory loss in March may be explained by the high incidence of influenza at this time. However, it is unclear why the incidence of the disease presents a second peak in May, when the incidence of respiratory viruses is relatively low. Climate conditions at this time might play a role in the susceptibility of the nasal epithelia towards certain viral infections, e.g. parainfluenza type III. CONCLUSION: Post-URTI olfactory dysfunction exhibits spring seasonality with peaks in March and May and possible causative factors being influenza and parainfluenza viruses (type III), respectively.

Adult↗

PubMed2005

Gustatory function in chronic inflammatory middle ear diseases.

HYPOTHESIS: Changes of gustatory function after ear surgery have been studied extensively. However, little is known on the influence of repeated/chronic inflammation within the middle ear on taste. STUDY DESIGN: Prospective study. MATERIALS AND METHODS: Forty-six patients suffering from either cholesteatoma (n = 25) or chronic otitis media mesotympanalis (n = 21) received quantitative gustatory tests. None of these patients had been operated on before these investigations. RESULTS: Side by side comparison showed a significantly lower taste function on the anterior two thirds of the tongue ipsilateral to the site of inflammation, regardless of the diagnosis. Further analyses exhibited a trend toward greater impairment in relation to the severity of the inflammatory process. CONCLUSION: These data are proof that taste function changes in relation to chronic middle ear diseases. It further shows that many of these alterations go unnoticed by the patients.

Cholesteatoma, Middle Ear↗

PubMed2003

Clinical presentation of qualitative olfactory dysfunction.

Many patients with olfactory dysfunction not only experience quantitative reduction of olfactory function, but also suffer from distorted olfactory sensations. This qualitative dysfunction is referred to as parosmia (also called "troposmia") or phantosmia, with the major difference that distorted olfactory sensations are experienced in the presence or absence of an odor, respectively. Our clinical observations corroborate the literature in terms of a general underestimation of the incidence of olfactory distortions. Based on selected cases we try to show that olfactory distortions exhibit a large variance in their clinical appearance. Further, emphasis is placed on the fact that only a detailed and directed history of the patient can provide cues to the correct diagnosis.

Adult↗

PubMed2002

Comparison of lateralized and binasal olfactory thresholds.

We investigated whether dirhinal olfactory thresholds differ from monorhinal ones. Experiments 1 and 2 investigated butanol, Experiment 3 phenylethylalcohol. In Experiments 2 and 3 pen-like odor dispensing devices were used, in Experiment 1 odors were presented in glass bottles. Participants were in excellent health (Experiment 1: 14 female [f], 15 m [m], mean age [ma] 24 years; Experiment 2: 12 f, 19 m, ma 24 years; Experiment 3: 19 f, 19 m, ma 32 years). Thresholds were assessed for left, right, and both nostrils. No significant difference was found between dirhinal results and results for the best of two nostrils. Apart from this, thresholds were found to improve with repeated testing. In conclusion, using two odorants with different techniques of administration in studies performed at different sites, the present results indicated that there is no major difference between odor detection thresholds obtained for the best and both nostrils.

Adult↗