Biomedical subjects

S Roscher

Publications and source records attributed to S Roscher.

17 recordsLinked to original sources

PubMed1998

Relation of olfactory event-related potentials to changes in stimulus concentration.

OBJECTIVE: The aim of this study was to investigate the influence of odorant concentration on the olfactory event-related potential (OERP). METHODS: OERP were evaluated in 8 men and 8 women (17-34 years of age) in response to 4 concentrations of vanillin (7, 28, 56 and 84% v/v). Sixteen presentations of each concentration (stimulus duration 200 ms, interval 40 s, flow 81/min) were applied in a randomized order. EEG recordings were made at 3 midline sites (pos. Fz, Cz, Pz). Amplitudes and latencies of four peaks were measured (latencies in ms at Pz after stimulation with 84% v/v vanillin): P1 (277), N1 (348), P2 (412) and P3 (496). Statistical analysis was performed with MANOVAs ('concentration', 'recording site' = within-subject-factors; 'age' as covariate). RESULTS: With increasing stimulus concentration amplitudes became significantly larger; this was most pronounced for P3 (P1N1: F = 2.90, P < 0.05; N1P2: F = 5.15, P < 0.01; N1P3: F = 35.7, P < 0.001; P3: F = 38.6; P < 0.001). Correspondingly, latencies shortened with increasing concentrations (P1: F = 25.2; N1: 17.51; P2: 14.8; P3: 13.4; all P < 0.001). While there was no correlation between OERP amplitudes and butanol odor detection thresholds, latencies were the shorter the lower the subjects' thresholds (coefficients of correlations for peak latencies at Cz for 84% v/v: P1 rl5 = -0.59; N1 rl5 = 0.58; P2 r15 = -0.55; P3 r15 = -0.45). CONCLUSIONS: The results indicated that both OERP amplitudes and latencies are related to the concentration of olfactory stimuli. They also suggested that latencies exhibit a stronger relation to changes in stimulus intensity compared to OERP amplitudes.

Adolescent↗

PubMed1996

Intranasal chemoreception in patients with multiple chemical sensitivities: a double-blind investigation.

Multiple chemical sensitivities (MCS) has become an increasingly frequent diagnosis assigned to patients with symptoms associated with exposures to environmental chemicals. Since the characteristic symptoms of MCS are triggered by very low concentrations of chemicals, in the range of olfactory thresholds, it is widely believed that the intranasal chemoreceptive senses are involved in the pathophysiology of MCS. Thus, the present study addressed both the olfactory and trigeminal systems: using a double-blind approach we investigated whether MCS patients show differences in responses after exposure to either room air or low concentrations of a widely used chemical agent (2-propanol). A total of 23 patients participated in the experiments (mean age 47 years; 13 female, 10 male). MCS was diagnosed according to Cullen's criteria Performance of the nasal chemical senses was established by means of chemosensory event-related potentials (CSERP) and subjective measures of olfactory function (odor discrimination, phenylethyl alcohol odor thresholds). CSERP were recorded in response to olfactory (H2S), and trigeminal (CO2) stimuli. The study provided three major results: (1) Approximately 20% of patients diagnosed with MCS presented symptoms regardless of the type of challenge, suggesting the susceptibility of MCS patients to unspecific experimental manipulations. (2) Changes in CSERP latencies indicated a change in the processing of both olfactory and trigeminal stimuli. (3) While odor threshold remained unchanged, the patients' ability to discriminate odors decreased after exposure to room air. In contrast, this decrease was less pronounced after exposure to 2-prop. Summarily, MCS patients respond to challenge with 2-prop with changes of chemosensory perception which might increase their susceptibility to environmentally volatile chemicals. Changes in the pattern of event-related potentials are interpreted as the possible change of the orientation of cortical generators, i.e., neuronal populations that were involved in the processing of chemosensory information. However, investigations in healthy controls are needed in order to draw further conclusions.

1-Propanol↗

PubMed1996

Assessment of analgesia in man: tramadol controlled release formula vs. tramadol standard formulation.

OBJECTIVE: The present study tested analgesia produced by a new controlled release formulation of tramadol. The investigation employed an experimental pain model based on chemo-somatosensory event-related potentials (CSSERP) in response to painful chemical stimuli applied to the nasal mucosa. STUDY: Twenty healthy volunteers participated in the experiments, which followed a controlled, randomised, double-blind, 3-way cross-over design. Each of the three medications (tramadol 100 mg [T100], tramadol controlled release 100 mg [TCR100] and tramadol controlled release 150 mg [TCR150]) was administered orally to fasting subjects. There was at least a 6 day washout period between tests. Each experiment was divided into five sessions, which took place before and 2, 4, 6, and 12 h after drug administration. In addition to the assessment of CSSERP, subjects rated the intensity of both the tonic and phasic painful stimuli. Nonspecific drug effects were also monitored by means of frequency analysis of the spontaneous EEG, ratings of adverse effects, and the subjects' performance in a tracking task. RESULTS: The significant reduction of amplitude N1 at central recording positions indicated that TCR 150 was the most effective analgesic 12 h after administration. Both 6 and 12 h after administration TCR 100 was more effective in terms of analgesia compared to T100. In addition, TCR100 appeared to produce fewer adverse effects than the standard formulation of tramadol. CONCLUSIONS: The controlled release formulation can be expected to become a valuable tool in peroral therapeutic regimens for chronic pain.

Adult↗

PubMed1996

Loss of olfactory function leads to a decrease of trigeminal sensitivity.

Healthy controls were compared to patients with decreased olfactory sensitivity (n = 32) to investigate interactions between the olfactory and trigeminal systems. Amplitudes of chemo-somatosensory event-related potentials in response to suprathreshold trigeminal stimuli (CO2) were found to be smaller in patients (P < 0.05) indicating a decrease of trigeminally mediated sensations.

Action Potentials↗

PubMed1996

"Sniffin' sticks": screening of olfactory performance.

"Sniffin' Sticks" is a new test of nasal chemosensory performance based on pen-like odour-dispensing devices. This portable test is suited for repetitive, inexpensive screening of odour identification. The test includes a forced odour-identification task for seven odours performed by means of a list of four items (multiple-choice). In 146 subjects the basic screening test was compared to a down-scaled version of the UPSIT (CC-SIT). Sniffin' Sticks exhibited a relatively higher coefficient of correlation with the subjects' age; they also demonstrated the women's superior olfactory sensitivity more pronounced when compared to men. In addition, the coefficient of correlation between age and olfactory performance was slightly higher when the sticks were used. Preliminary investigations in nine patients with impaired olfactory function (i.e., anosmic or hyposmic patients) revealed significantly lower scores in patients compared to healthy controls matched for age and sex (p < 0.001). It is concluded that Sniffin' Sticks may be useful in the routine clinical assessment of olfactory performance where both time and costs matter.

Adult↗

PubMed1995

Tonic pain evoked by pulsating heat: temporal summation mechanisms and perceptual qualities.

The properties of a newly developed tonic heat pain model (THPM), which makes use of pulsating contact heat, were investigated in 18 young men. The most important feature of this model is that repetitive heat pulses with an intensity of 1 degree C above the individual pain threshold are employed. This approach was used to tailor the tonic pain stimulation to the individual pain sensitivity. In the first of two experiments, the effects of pulse frequencies ranging from 5 to 30 pulses per minute (ppm) on ratings of pain intensity and pain unpleasantness (visual analogue scales) were examined. At all frequencies, both ratings increased steadily over the 5-min test period. Frequencies of 15 ppm or more appeared to enhance pain intensity throughout the test period compared to the lower frequencies, but did not appear to alter pain unpleasantness. This suggests that only pain intensity is influenced by slow temporal summation and that a sort of frequency threshold exists for this kind of summation. In the second experiment, the THPM was compared to a well-established form of tonic pain stimulation, the cold-pressor test (CPT); visual analogue scales were again used, and in addition the McGill Pain Questionnaire was employed. The CPT appeared to produce stronger tonic pain than the THPM. However, as is typical with tonic pain, both tonic pain models induced relatively higher values on the affective pain dimension than on the sensory pain dimension. The time course of pain was dynamic in the CPT, with an increase followed by a plateau phase, at least in those subjects who could tolerate the CPT for more than 60 sec. In contrast, as in the first experiment, the pain ratings in the THPM were characterized by a slow and steady increase over time. Moreover, there was absolutely no indication of a dichotomy between "pain-sensitive" and "pain-tolerant" individuals in the THPM, although such a dichotomy was evident in the CPT. This implies that the distinction between pain-sensitive and pain-tolerant individuals can be made only with the CPT, and that this distinction represents individual differences in peripheral vascular reactions to cold rather than in pain perception. In conclusion, the THPM appears to produce a stable and predictable temporal pattern of tonic pain with a predominant affective component, and to be suitable for application in the majority of individuals without causing undue discomfort.

Adult↗

PubMed1993

Theoretical and empirical considerations on the relation between 'body image', body scheme and somatosensation.

The authors first discuss possible interactions between the hitherto neglected neurophysiological and neuropsychological factors and the traditionally accepted cognitive and affective factors in 'body image' formation. They then report on a study of the relation between body size perception (video distortion technique, image marking procedure, kinaesthetic size estimation apparatus) and somatosensation (thermal, pain and vibration thresholds) in young women. Included in the study were questionnaires on eating behaviour and motivation, body attitude or body satisfaction, and depressive mood and thoughts. Neither the somatosensory nor the questionnaire variables explained the difference between 'overestimators' and 'underestimators' of body size. However, these variables did explain the difference between 'good perceivers' and 'poor perceivers' (degree of deviation from actual body size) in the video distortion technique, with a somewhat larger contribution by the somatosensory variables. The latter finding, although clearly preliminary, should stimulate further investigations of the relationship between somatosensory variables and body size perception.

Adult↗

PubMed1993

Pain sensitivity in recovered anorexics, restrained and unrestrained eaters.

The heat pain threshold and local skin temperature were assessed in 23 former anorexic in-patients with an 'intermediate' (N = 9) or 'good' outcome (N = 14) and in 21 restrained and 20 unrestrained eaters. All subjects were female. The group means of the pain thresholds did not differ significantly from each other, suggesting that the homogeneous increase in pain thresholds we had previously observed in acutely ill eating disorder patients is state dependent. However, a sizeable percentage of the restrained eaters (29%) had pain thresholds clearly above the normal range. Thus it may well be that restrained eating carries a risk of reducing pain sensitivity. Pain threshold and skin temperature correlated significantly (r = -0.63) only in the group of patients with an intermediate outcome, a finding resembling that obtained in acute anorexics. This suggests that peripheral thermoregulation and pain sensitivity are linked in the acute and moderately improved phases of anorexia nervosa.

Adult↗

PubMed1992

Body size perception and body satisfaction in restrained and unrestrained eaters.

In 21 restrained and 20 unrestrained eaters body size perception was measured using the video distortion technique (VDT), the image marking procedure (IMP) and the kinesthetic size estimating apparatus (KSEA). Body satisfaction was assessed by questionnaires (Body Shape Questionnaire, Dieting scale of the Eating Attitudes Test). Restrained eaters showed no systematic over- or underestimation of the body size but less perceptual accuracy (in VDT and KSEA). Furthermore, they were clearly more dissatisfied with their bodies than unrestrained eaters. Both findings were unrelated to each other. In both groups depressive mood or thoughts seemed to be associated with body dissatisfaction but not with body size misperception. Objective body measures (body mass index, body fat content) were not related to either body size perception or body satisfaction. The findings suggest that a perceptual uncertainty in regard to body size (either for visual or for somatosensory aspects) has already developed in restrained eaters, which may constitute a predisposition for more overt forms of body size misperception as found in eating disorder patients.

Behavior Therapy↗

PubMed1969