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Biomedical subjects

T Hummel

Publications and source records attributed to T Hummel.

152 records · Page 9Linked to original sources
PubMed1989

Is there directional smelling?

The aim of the present study was to establish the crucial precondition for directional smelling, i.e. the ability of humans to discriminate between odorous stimuli perceived either from the right or from the left side. When the 'pure' odorants hydrogen sulphide or vanillin were used as stimulants localization was random. On the other hand stimulation with carbon dioxide or menthol yielded identification rates of more than 96%. These results established the fact that directional orientation, considering single momentary odorous sensations, can only be assumed, when the olfactory stimulants simultaneously excite the trigeminal somatosensory system.

Adult↗
PubMedDate not supplied

Genetic analysis of axon pattern formation in the embryonic CNS of Drosophila.

The major axon tracts in the embryonic CNS of Drosophila are organised in a simple, ladder-like pattern. Each neuromere contains two commissures which connect the contra-lateral sides and two longitudinal connectives which connect the different neuromeres along the anterior-posterior axis. The commissures form in close association with only few cells located at the CNS midline. The formation of longitudinal connectives depends in part on the presence of specific lateral glial cells. To unravel the genes underlying the formation of the embryonic CNS axon pattern, we conducted a saturating F2 EMS mutagenesis, screening for mutations, which disrupt this process. The analyses of the identified mutations lead to a simple sequential model on axon pattern formation in embryonic CNS.

Animals↗
PubMedDate not supplied

Chemosensory event-related potentials in man: relation to olfactory and painful sensations elicited by nicotine.

The aim of this study was to investigate the topographical distribution of chemosensory event-related potentials in relation to stimulation with nicotine. The recognition thresholds of 3 different sensations elicited by nicotine (odor, burning, stinging) were determined. Subsequently, 3 concentrations of nicotine were applied which were just above mean threshold for each of the 3 sensations. Subjects rated the intensity of odor, burning, and stinging. Additionally, they tracked the time course of these sensations. Odor and stinging appeared immediately after stimulus onset. Burning started after several seconds. Intensity ratings of burning and stinging increased with rising stimulus concentrations, whereas the odorous sensation was strongest at medium concentrations. After low and medium stimuli largest mean amplitudes were parietally obtained, whereas following stimulation with the highest concentration, amplitudes peaked at Cz.

Adult↗
PubMedDate not supplied

Differences in human evoked potentials related to olfactory or trigeminal chemosensory activation.

The aim of the present study was to determine, whether there are differences in the topographical distribution of chemosensory evoked potentials (CSEPs) due to stimulation with different odorous substances. The odorants used in the study which mainly excited the olfactory nerve were vanillin and acetaldehyde; those which additionally excited the trigeminal nerve were sulphur dioxide and ammonia. Twelve subjects participated in the study. The subjects separately estimated the intensity of the odorous and of the painful/pricking sensation caused by the stimuli, and described the odorous qualities in their own words. CSEPs were recorded from 7 positions. After stimulation with "olfactory" substances maximum CSEP amplitudes were recorded at parieto-central sites, and after stimulation with "trigeminal" substances maximum amplitudes were obtained at the vertex. Following stimulation with ammonia and sulphur dioxide amplitudes were largest contralateral to the stimulated nostril. In contrast, little difference in CSEP amplitudes was observed between hemispheres after stimulation with vanillin or acetaldehyde. Thus, the topographical distribution of CSEP amplitudes may provide information with regard to the sensory system (olfactory or trigeminal) activated by the presentation of an odorous stimulus.

Acetaldehyde↗
PubMedDate not supplied

Decreased trigeminal sensitivity in anosmia.

The present study aimed to investigate intranasal trigeminal sensitivity in a large sample of patients with anosmia due to different etiologies. We investigated the trigeminal detection threshold for formic acid in healthy controls (n = 96) and patients with anosmia due to head trauma (n = 18) or sinonasal disease (n = 54). Anosmics exhibited higher thresholds compared with normosmics (p < 0.001). In addition, thresholds were found to be higher in patients with posttraumatic anosmia compared to anosmics with sinonasal disease (p < 0.001). The data indicate that (1) loss of olfactory sensitivity in humans may be associated with a decreased sensitivity towards trigeminal stimuli and (2) alteration of intranasal trigeminal function is stronger in patients with posttraumatic anosmia compared to patients with sinonasal disease. This may have implications for the medicolegal investigation of anosmic patients where trigeminal stimuli are frequently used to assess the patient's response bias.

Adolescent↗
PubMedDate not supplied

Chemosensory function and response in idiopathic environmental intolerance.

This chapter reviews the current literature on the possible role of olfactory and trigeminal chemosensory function in idiopathic environmental intolerances (IEI). Two general points emerge from the review. First, studies of chemosensory function in IEI patients indicate that, despite their self-reported "heightened sensitivity" and enhanced responsivity to environmental odors, when compared to healthy controls they generally are found to be equally or even less sensitive to odors as measured by objective psychophysical and electrophysiological measures of olfactory function. These studies point towards alterations in the cognitive processing of olfactory information as the major characteristic of IEI. Second, studies of the role of sensitivity and bias in olfactory and trigeminal chemosensory functioning indicate that nonsensory factors (e.g., attention, bias, personality) can dramatically alter the self-reported impact of exposure to volatile chemicals. Together, these general points suggest a perspective on IEI that views many symptoms of the disorder to primarily reflect the influence of nonsensory, cognitive processes on responses to environmental odors.

Chemoreceptor Cells↗
PubMedDate not supplied

Olfactory (chemosensory) event-related potentials.

Chemosensory event-related potentials (CSERPs) have found their way into a number of fields of research where they help to determine the function of both the trigeminal and the olfactory system. The investigation of chemosensory deficits in patients with Parkinson's or Alzheimer's disease is only one of the typical applications. It can be assumed that scientists involved in research on patients with multiple chemical sensitivities will also benefit from having access to objective data covering different aspects of the sense of smell.

Electrophysiology↗