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Biomedical subjects

R Ferstl

Publications and source records attributed to R Ferstl.

At least 19 recordsLinked to original sources
PubMed2006

Grasp effects of the Ebbinghaus illusion are ambiguous.

The assumption that the Ebbinghaus/Titchener illusion deceives perception but not grasping, which would confirm the two-visual-systems hypothesis (TVSH) as proposed by Milner and Goodale (The visual brain in action, 1995), has recently been challenged. Franz et al. (Exp Brain Res 149:470-477, 2003) found that the illusion affects both perception and grasping, and showed that the effect of the illusion on the peak grip aperture (PGA) cannot be accounted for by different sizes of the gap that separates the central target disk from the surrounding flankers. However, it is not yet clear if the presence of flankers per se influences grasping. We therefore compared kinematic parameters of prehension, using the Ebbinghaus illusion, and a neutral control condition where normal subjects grasped a disk without any flankers. In accordance with the well-known effects of the illusion on perceived size, the PGA was smaller when the target disk was surrounded by large flankers, and larger when it was encircled by small flankers. However, the largest PGA values were reached in the neutral control condition. Hence the presence of flankers leads to a general reduction of the PGA, possibly because the flankers are regarded as obstacles. This 'reduction effect' casts doubts on how appropriate it is to directly compare perceptual measures and PGA values when using the Ebbinghaus illusion. Even smaller effects of the illusion on the PGA compared to larger perceptual effects cannot be unequivocally interpreted.

Adult↗
PubMed2001

Olfactory event-related potentials in patients with brain tumors.

OBJECTIVE: The aim of the study was to determine how odor processing is altered in patients with unilateral supratentorial brain tumors. METHODS: Olfactory event-related potentials (OERPs) were evaluated in 10 patients with unilateral brain tumors of the frontal or temporal lobe in response to linalool and allylcaproate. Both odors were presented monorhinally by a constant-flow olfactometer. In addition, 20 healthy subjects were examined. While sniffing, the subjects were asked to discriminate the two odors. EEG was recorded from 7 electrode positions (Fz, Cz, Pz, F3/4, P3/4). Amplitudes and latencies of 3 peaks (N1, P2, P3) were measured. To control for effects of modality-non-specific alterations on the olfactory components acoustic event-related potentials (AERPs) were registered by use of an oddball paradigm. RESULTS: Patients with right-sided lesions showed distinct deficits in the discrimination task after stimulation of the right and left nostril. In contrast, patients with left-sided lesions only had an attenuation of correct reactions after left-sided stimulation. In the OERPs, patients with right-sided lesions showed P2- and P3-components with decreased amplitudes at parietal electrode positions. These alterations appeared after ipsi- and contralateral stimulation. Patients with left-sided lesions showed a significant effect of the side of stimulation. Their OERP-amplitudes were decreased after left-sided stimulation but not after right-sided stimulation. After right-sided olfactory stimulation a correlation between the olfactory and the acoustic ERP was seen in patients with right-sided lesions. CONCLUSIONS: Olfactory performance of the participating patients was markedly reduced. Patients with right-sided lesions showed bilateral impairment, which would support the importance of the right hemisphere in olfaction. The alteration of the topographic distribution of P2- and P3-amplitudes in patients with right-sided lesions might reflect an impairment of early and late olfactory processing steps.

Acyclic Monoterpenes↗
PubMed2001

Children's spatial behavior is differentially affected after traumatic brain injury.

Spatial behavior in 20 children with severe traumatic brain injury (TBI) and 20 healthy controls was investigated using the Kiel Locomotor Maze. Children had to remember defined locations in an experimental chamber with completely controlled intra- and extra-maze cues until learning criterion was reached. In a second experiment, spatial orientation strategies were assessed. Children with TBI were shown to be impaired in spatial learning and spatial memory. Spatial orientation was found to be deficient even in cases where spatial learning and memory proved to be unimpaired, especially in tasks that demanded the use of relational place strategies. Children who suffered a TBI at an early age proved to be more severely impaired in spatial learning and orientation than older children.

Brain Injuries↗
PubMed1999

Is odor processing related to oral breathing?

This paper addresses two questions related to the inherent association between breathing and odor perception: Does central nervous processing of odors change when an artificial breathing technique (velopharyngeal closure) is introduced and secondly, does odor processing vary with the oral breathing phase (inhalation or exhalation)? Chemosensory event-related potentials (CSERP) were obtained from eight female subjects while they were smelling an odor mixture (citral, eugenol, linalool, menthol and isoamylacetate). Each subject was required to perform spontaneous mouth breathing (120 trials) as well as the velopharyngeal closure technique (120 trials). Simultaneously, a thermistor monitored the phase of the respiratory cycle. The results reveal that the central nervous correlates of odor processing change with the breathing technique but not with the oral breathing cycle. The findings that early stimulus processing is faster (N1 latency) and late stimulus processing more pronounced (P3 amplitudes) when the subjects are breathing spontaneously are discussed with regard to attentional effects. The reduction of the N1 amplitude during the spontaneous breathing condition may be caused by larger latency variations and longer stimulus rise-times. Furthermore, it is concluded that the oral breathing cycle is less important than the nasal breathing cycle for olfactory information transmission.

Adult↗
PubMed1999

[Inducibility of olfactory sensitivity by odor exposure of persons with specific anosmia].

Insensitivity to single odors, called specific anosmia, has been repeatedly reported in the literature. The main question of the present study was whether olfactory sensitivity is inducable in subjects with specific anosmia. For this reason the olfactory sensitivity of women with specific anosmia to the volatile steroid androstenone was investigated by threshold measurements at two times, before and after repeated odor exposure. Androstenone is a compound that contributes to human body odor and is found at a higher concentration in male axillary sweat than in female sweat. The results show that in more than 80% of the odor exposed anosmics olfactory perception of androstenone could be induced.

Adult↗
PubMed1998

Central nervous correlates of chemical communication in humans.

The recording of chemosensory event-related potentials (CSERPs) has been established as an objective method in the assessment of central odor processing in humans. In the present study CSERPs were used to investigate whether human body odor is genetically determined by the major histocompatibility complex (MHC), referred to in humans as the human leukocyte antigen (HLA). The immunological function of the MHC is the discrimination of self/nonself within the immune system. In rodents it has been shown that body odor is significantly influenced by the MHC and that it can be discriminated by members of different species. To create a sufficiently large subject pool, 144 subjects were screened for their HLA class I loci A and B. During the electroencephalography (EEG) session the subjects (n = 40/20 women) were confronted with the body odor (axillary hair) of three different donors. Two donors (d1 and d2) were HLA-similar but had a different HLA type than the third donor (d3) and the perceiving subject. The third donor and the perceiver shared a similar HLA type. Half of the perceivers received odors from donors of the same sex, the other half smelt odors from donors of the opposite sex. In the EEG session subjects were presented with 200 trials. The odors were delivered through a constant flow olfactometer non-synchronously to breathing. The odor of d1 appeared frequently (p = 0.6) whereas the odors of d2 and d3 appeared each at a rate of p = 0.2. During half the trials the subjects were instructed to respond to the odor of d2, during the other half to the odor of d3. The EEG was recorded from Fz, Cz, Pz, F3, P3, F4 and P4 in reference to linked mastoids. First results show that male perceivers show enhanced potentials in response to male donors of a similar HLA type (d3). The CSERP results of the other groups as well as valence and attractiveness ratings will be discussed.

Adult↗
PubMed1998

Attentional modulation of central odor processing.

Two studies were conducted to investigate the influence of attention on the components of the chemosensory event-related potential (CSERP). In the first study the odors linalool and eugenol were delivered to six male subjects, in the second study three male and two female subjects were presented with their own body odor (axillary hair) and the body odor of a same sex donor. In both studies the odors were presented in an oddball paradigm under ignore and attend conditions via a constant-flow olfactometer. In the ignore condition attention was diverted from the odors with a distractor task, while in the attend condition the subjects were asked to respond to the infrequently occurring odor. In both studies the allocation of attention led to a decrease in the latency of the early components (N1, P2, N2) and to an increase in the amplitude of the late positivities. The modulation of the early components suggests that attentional gating in olfaction might already be effective at an early processing level.

Acyclic Monoterpenes↗
PubMed1998

Development of spatial memory and spatial orientation in preschoolers and primary school children.

The present study addresses the question of what kind of information children use when orientating in new environments, if given proximal and distal landmarks, and how spatial memory develops in the investigated age groups. Ten 5-year-old, ten 7-year-old and ten 10-year-old children were presented with the 'Kiel Locomotor Maze', containing features of the Radial Arm Maze and the Morris Water Maze, in order to assess spatial memory and orientation. Children had to learn to approach baited locations only. Task difficulty was equated with respect to the children's age. Training was given until the children reached criterion. During testing, the maze configuration and response requirements were systematically altered, including response rotation, cue rotation, cue deletion and response rotation with cue deletion in order to assess the spatial strategies used by the children. During training and testing, working-memory errors (WM), reference-memory errors (RM) and working-reference memory errors (WR) were recorded. As expected, no difference between age groups appeared during training, thus confirming comparable task difficulty across age groups. During testing, age groups differed significantly with regard to the orientation strategy used. The 5-year-olds were bound to a cue strategy, orientating towards local, proximal cues. The 10-year-olds mastered all tasks, thus displaying a place strategy, being able to use distal cues for orientation, and were even able to do so after being rotated 180 degrees. The 7-year-olds proved to be at an age of transition: five of them were bound to a cue strategy, five children were able to adopt a place strategy. The differences in the orientation strategies used by children of different age groups was reflected by the sum of errors they made, also by RM. WM were found to be rare, especially in older children. We conclude that preschoolers use a cue strategy, that the development of place strategies occurs during primary school age and seems to be complete by the age of 10 years.

Age Factors↗
PubMed1997

Fractionation and bioassay of human odor types.

Human urine samples were fractionated to examine the contribution of volatiles to the individual body odor. The samples were obtained from 4 male donors and fractionated using a vacuum technique. The volatiles from the chemical fractions were analyzed using the CLSA technique and gas chromatography. Thereafter, these fractions were tested in a computer-controlled olfactometer by trained rats. Although the rats were able to discriminate the distillation residue, they could not recognize the urine odor in the distilled fraction. The results of gas chromatography indicate a continuous release of volatile constituents in the distillation residue.

Adult↗
PubMed1997

Central processing of odor concentration is a temporal phenomenon as revealed by chemosensory event-related potentials (CSERP).

Chemosensory event-related potentials (CSERP) can be used to examine central nervous odor processing. An important question for understanding odor perception is how different concentrations are processed. In the present study two odors were chosen which activate either the olfactory (linalool) or the trigeminal (menthol) system. Both odors were presented to 11 subjects in four different concentrations. Four subjects had to attend actively to the odors while the others perceived the odors under passive attention. The results showed that increased concentrations of the olfactory stimulus resulted in shorter latencies of the N1 component but did not affect the amplitudes of the CSERP. However, the amplitudes of the stimulus dependent, exogenous components (N1, P2) increased with higher concentrations of the trigeminal stimulus. The amplitude of the late positive complex, which reflects endogenous processes, was usually larger when the odorous stimuli had to be attended to actively. It is concluded that olfactory intensity coding results in a qualitatively different but not in a stronger neuronal response of the human brain.

Adult↗
PubMed1996

Olfactory information processing during the course of the menstrual cycle.

In the present study we examined whether olfactory information processing depends on the phase of the menstrual cycle. Five female subjects were investigated during three phases (follicular, ovulatory, luteal) of their menstrual cycle. In each session chemosensory (olfactory) event-related potentials (CSERP) were recorded and olfactory thresholds and the hedonic tone of the test stimulus (citral) were determined. Threshold values were correlated with the salivary cortisol level. The results show that olfactory perception changes during the menstrual cycle. After the first stimulus presentations in a recording session, odors were perceived as more complex or novel during the ovulatory period (enhanced amplitude of P3-1). With continued stimulation, odor processing became faster (reduced latency of NI, P2 and P3-2) around ovulation and slower during the follicular phase. Moreover, odors were described more differentially during the ovulatory period. Olfactory sensitivity was correlated positively with the peripheral cortisol level.

Adult↗
PubMed1996

MHC-associated and MHC-independent urinary chemosignals in mice.

The chemosensory identity of mice, rats, and humans is determined partly by polymorphic genes of the major histocompatibility complex (MHC). In inbred strains of mice as well as in seminatural populations MHC-associated mating preferences selectively influence reproductive success. To explore MHC-associated chemosignals in relation to otherwise genetically determined chemosignals a first study was conducted on seven trained rats' responses to the odors of inbred strains of mice. Results of the first study confirmed that neither the MHC nor genes in the genetic background dominate in determining urine odor specificity of mice and that specific olfactory cues associated with either the MHC or the genetic background can be identified by olfaction. In a second study, these specific olfactory cues were analyzed by means of gas chromatography. The results indicate that specific volatile components associated with either the MHC or the genetic background can be found in mouse urine odor, and that profiles of ubiquitous volatile components show some association with either the MHC or the genetic background. Furthermore, results show that a small number of specific compounds as well as a profile of some few ubiquitous volatiles constitute MHC-associated odor cues and that influences of the MHC and genes in the genetic background interact in constituting urine odor specificity in mice.

Animals↗
PubMed1996

Analgesic effect of ceruletide in men is limited to specific pain qualities.

Cholecystokinin (CCK) and related peptides are supposed to be potent analgesic neuropeptides. Studies in rodents suggest a dose-dependent biphasic effect. The present study aimed to examine the pain modulating effect of different doses (0.5 microgram and 5 micrograms) of ceruletide (CRL), infused i.v. for 30 min. Pain thresholds were obtained for ischemic, mechanical, and thermal pain. In addition, pain tolerance was measured for mechanical pain. According to a placebo-controlled double-blind within-subject design 25 healthy men attended three experimental sessions each. Pain perception was measured as a baseline and twice after the infusion. The effect of both doses of CRL to enhance the pain threshold for thermal stimuli is in line with former studies. However, perception of heat stimuli above or below the threshold was not substantially affected by CRL treatment. Algesic properties of CRL are also indicated, because the tolerance for mechanical pain decreased after administration of the high dose of CRL. Perception of ischemic pain was not obviously influenced by any of the treatments. The role of CRL in human pain modulation seems to vary, depending on the type of experimental pain.

Adult↗
PubMed1996

Effects of modality shift and motor response shift on simple reaction time in schizophrenia patients.

The modality shift effect (MSE) shows that the reaction time (RT) of schizophrenia patients is longer when successive imperative stimuli are of different modality (e.g., light followed by sound) than when they are identical (e.g., sound followed by sound). The authors analyzed the RTs of 49 men: 21 had schizophrenia, 13 were alcoholic, and 15 were controls. The results from a standard paradigm to provoke the MSE indicated a considerably more pronounced MSE in schizophrenia patients than in the comparison groups. Another experimental condition was used to test whether the effect is due to the longer activity of neural traces in sensory pathways in schizophrenia patients or to changes in an entire stimulus response cycle. Results suggest that only a shift in modality and not in the required motor response lengthened the RTs of the schizophrenia patients more than of the other groups.

Adult↗
PubMed1996

The nature of the late positive complex within the olfactory event-related potential (OERP).

The olfactory event-related potential (OERP) has been described as being dependent on exogenous stimulus features, but no effort has been made to examine possible endogenous determinants. We wanted to separate exogenous and endogenous components of the OERP by using an olfactory oddball paradigm. A high concentration of citral was used as the target stimulus, and a low concentration was used as the standard stimulus. Odors were presented within a constantly flowing air stream. We found that the early components of the OERP (N1, P2) are modulated by the stimulus concentration, whereas the late positive components (P3-1, P3-2) vary depending on the subjective stimulus significance and stimulus probability. It is concluded that the positive component of the OERP, which has been formerly explained by chemical and physical stimulus features, is actually determined by endogenous processes.

Acyclic Monoterpenes↗
PubMed1994

Soluble MHC class I molecules in human body fluids.

Apart from their well-known function of antigen presentation in the form of peptides, major histocompatibility antigens (MHC) have been found to be unique markers of individual body odors in murine experimental models. In the current study we examined the nature and expression of soluble human MHC class I molecules in body fluids. Biochemical analysis of affinity purified serum class I molecules revealed a variety of molecules within the molecular weight region of 45 to 21 kD. SDS-Western blotting of HLA derived from hepatocytes and spleen cells suggested that much of the small molecular mass fraction of sHLA (< 45 kD) found in serum is derived from the liver. sHLA were detected and quantitated in serum, plasma, urine, cerebrospinal fluid, and sweat. No sHLA were detectable in cerebrospinal fluid (n = 20). In addition, sHLA was measured in serum of women during the menstrual cycle. A significant increase in sHLA was observed during the first half of the cycle, suggesting that sexual hormones may increase sHLA concentration. The observed increase was most prominent in women that were HLA-A24.

Adult↗
PubMed1994

Is the modality-shift effect specific for schizophrenia patients?

Several studies have found that the reaction time of schizophrenia patients is longer when successive imperative stimuli are of different modality (e.g., light followed by sound) than when they are identical (e.g., sound followed by sound). This effect is called the modality-shift effect. In this study, the reaction times of 175 persons were analyzed: 54 schizophrenia patients, 33 patients with mood disorders, 13 alcoholics, 17 patients with rheumatoid arthritis, 13 patients with internal diseases, and 45 normal controls. The results indicated that a shift from light to sound stimuli lengthened the reaction time for schizophrenia patients considerably more than for alcoholics, patients with rheumatoid arthritis, patients with internal diseases, or normal controls. No difference was found between the reaction times of schizophrenia patients and patients with mood disorders.

Adult↗