Biomedical subjects

B Röder

Publications and source records attributed to B Röder.

At least 19 recordsLinked to original sources

PubMed2001

Auditory memory in congenitally blind adults: a behavioral-electrophysiological investigation.

Blind people must rely more than sighted people on auditory input in order to acquire information about the world. The present study was designed to test the hypothesis that blind people have better memory than sighted individuals for auditory verbal material and specifically to determine whether memory encoding and/or retrieval are improved in blind adults. An incidental memory paradigm was employed in which 11 congenitally blind people and 11 matched sighted controls first listened to 80 sentences which ended either with a semantically appropriate or inappropriate word. Immediately following, the recognition phase occurred, in which all sentence terminal words were presented again randomly intermixed with the same number of new words. Participants indicated whether or not they had heard the word in the initial study phase. Event-related brain potentials (ERPs) were recorded from 28 electrode positions during both the encoding and the retrieval phase. Blind participants' memory performance was superior to that of sighted controls. In addition, during the recognition phase, previously presented words elicited ERPs with larger positive amplitudes than new words, particularly over the right hemisphere. During the study phase, words that would subsequently be recognized elicited a more pronounced late positive potential than words that were not subsequently recognized. These effects were reliable in the congenitally blind participants but could only be obtained in the subgroup of sighted participants who had the highest memory performance. These results imply that blind people encode auditory verbal material more efficiently than matched sighted controls and that this in turn allows them to recognize these items with a higher probability.

Adult↗

PubMed2000

Inhibition of return and oculomotor control in the blind.

Our attentional systems orient reflexively to novel environmental stimuli. Such attentive orienting is typically followed by a prolonged period of inhibition, known as inhibition of return (IOR), thought to be linked to the eye movement system. It is widely believed that IOR may provide a tagging mechanism that prevents perseveration, and thus facilitates attentional search. Using a tactile variant of the peripheral spatial cuing paradigm, we show IOR in congenitally blind adults and in an individual who had no eyes. These results demonstrate for the first time that spatial IOR can occur in the absence of oculomotor control.

Adult↗

PubMed2000

Event-related potentials during auditory language processing in congenitally blind and sighted people.

While behavioral studies have documented delayed language acquisition in blind children, other studies have revealed better speech discrimination abilities for blind than sighted adults. Several brain imaging studies have provided evidence for cortical reorganization due to visual deprivation but the cerebral organization of language in blind humans is not known yet. We hypothesized that the increasing specialization of language systems normally observed during development may not take place to the same degree in blind individuals since posterior visual areas do not receive their adequate input. On the other hand, we hypothesized that blind people, due to their greater reliance upon the auditory language signal, may process speech faster than sighted people. To test these assumptions, event-related potentials were recorded while 11 congenitally blind and 11 sighted adults matched in age, gender, handedness and education were engaged in a language task. Participants listened to sentences in order to decide after each sentence if it was meaningful or not. Incongruous sentence-final words elicited an N400 effect in both groups. The N400 effect had a left-lateralized fronto-central scalp distribution in the sighted but a symmetric and broad topography in the blind. Furthermore, the N400 effect started earlier in the blind than in the sighted. Closed class compared to open class sentence middle words elicited a more pronounced late negativity in the blind than in the sighted. These results suggest that blind people process auditory language stimuli faster than sighted people and that some language functions may be reorganized in the blind.

Adult↗

PubMed2000

Photophysical studies of the pheophorbide a dimer.

This work reports on a monomer-dimer equilibrium state of pheophorbide a in solution. A methodology for controlling the equilibrium constant by use of temperature and solvent variation is described. The absorption spectrum of the dimer is calculated, using different prepared equilibria of monomer and dimer in solution. We propose that these aggregates provide a good model for understanding the dimerization process in tetrapyrroles.

Absorption↗

PubMed1999

Spatial attention to central and peripheral auditory stimuli as indexed by event-related potentials.

Young adult subjects attended selectively to brief noise bursts delivered in free-field via central and peripheral arrays of four loudspeakers each that were arranged along a semi-circle extending from the midline to 90 degrees right of center. Frequent "standard" stimuli (90%) and infrequent "target/deviant" stimuli (10%) of increased bandwidth were delivered at a fast rate in random order and equiprobably from all eight speakers. In separate runs, the subject's task was to selectively attend to the center or rightmost speaker, and to press a button to the infrequent "target" stimuli occurring at the designated (spatial) location. Behavioral detection rates and concurrently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended source. The attentional gradients were steeper for the central than the peripheral array, indicating that attention can be more sharply focused upon sound sources directly in front of the listener. The ERP data suggested that selection for location is accomplished in two distinct stages, with an initial broadly tuned filtering, followed by a more narrowly focused selection of attended-location deviants.

Acoustic Stimulation↗

PubMed1999

Improved auditory spatial tuning in blind humans.

Despite reports of improved auditory discrimination capabilities in blind humans and visually deprived animals, there is no general agreement as to the nature or pervasiveness of such compensatory sensory enhancements. Neuroimaging studies have pointed out differences in cerebral organization between blind and sighted humans, but the relationship between these altered cortical activation patterns and auditory sensory acuity remains unclear. Here we compare behavioural and electrophysiological indices of spatial tuning within central and peripheral auditory space in congenitally blind and normally sighted but blindfolded adults to test the hypothesis (raised by earlier studies of the effects of auditory deprivation on visual processing) that the effects of visual deprivation might be more pronounced for processing peripheral sounds. We find that blind participants displayed localization abilities that were superior to those of sighted controls, but only when attending to sounds in peripheral auditory space. Electrophysiological recordings obtained at the same time revealed sharper tuning of early spatial attention mechanisms in the blind subjects. Differences in the scalp distribution of brain electrical activity between the two groups suggest a compensatory reorganization of brain areas in the blind that may contribute to the improved spatial resolution for peripheral sound sources.

Adult↗

PubMed1999

Effects of interstimulus interval on auditory event-related potentials in congenitally blind and normally sighted humans.

To test the hypothesis of auditory compensation after early visual deprivation, congenitally blind and sighted adults performed an auditory discrimination task. They had to detect a rare target tone among frequent standard tones. Stimuli were presented with different interstimulus intervals (ISIs) (200, 1000, 2000 ms) and the auditory-event related potentials to all tones and reaction times to targets were recorded. Increasing ISIs resulted in an increasing amplitude of the vertex response (N1-P2) in both groups, but this amplitude recovery was more pronounced in the blind. Furthermore, targets elicited larger and more posteriorly distributed N2 responses in the blind than in the sighted. Since target detection times were shorter in the blind as well, these findings imply compensatory adaptations within the auditory modality in humans blind from birth.

Acoustic Stimulation↗

PubMed1998

13(2)-hydroxy-bacteriopheophorbide a methyl ester pharmacokinetics measurements with fluorescence versus absorption spectroscopy. Is there a difference?

OBJECTIVE: Quantification of photosensitizer concentration in tissue improves the planning and, subsequently, the outcome of photodynamic therapy. This study was designed to determine if the method of photosensitizer evaluation influences the accuracy of pharmacokinetic results. MATERIALS AND METHODS: In vivo 13(2)-Hydroxy-bacteriopheophorbide a methyl ester (13(2)-OH-BPME) pharmacokinetics in mice bearing LEWIS lung carcinoma was studied using fluorescence in situ and absorption spectroscopy (following photosensitizer chemical extraction) as photosensitizer quantification methods. The correlation of 13(2)-OH-BPME fluorescence intensity and its concentration using the absorption spectroscopy were determined for each tissue. RESULTS: The parenchymatous organs showed maximum 13(2)-OH-BPME concentration and fluorescence intensity at 2 h post-injection (lung, liver, spleen), and at 2 h post-injection in the kidney with both quantification methods (identical correlation). There was a difference in the time of maximum photosensitizer fluorescence intensity and its concentration in tumor, muscle, and skin (low correlation). The time of maximum fluorescence intensity in muscle, skin, and tumor was at 4 h, 12 h, and 12 h post injection respectively while its maximum concentration was at 2 h, 4 h, and 8 h post-injection. CONCLUSION: The method of photosensitizer evaluation affects the accuracy of its pharmacokinetic results.

Animals↗

PubMed1997

Slow negative brain potentials as reflections of specific modular resources of cognition.

The paper summarizes a series of experiments in which the topography and the amplitude of slow event-related brain potentials (slow ERPs) was studied in cognitive tasks which imposed different amounts of load on functionally distinct processing modules. The results suggest that the topography of slow ERPs reflects the relative activation/inactivation of distinct cortical cell assemblies while the absolute amplitude of the negative maximum seems to reflect how much a particular cell assembly is activated at a particular time. Translated into the terminology of cognitive resource theories one could say that tasks which evoke distinct slow wave patterns draw on independent resources. Likewise, the amplitude of a slow wave pattern could be related to the construct of resource allocation, i.e. the larger the amplitude of a slow wave pattern the more resources of a particular type are allocated to a task. These findings are discussed with respect to possible generator mechanism of slow waves and in relation to possible causes of capacity limitations of the human information processing system.

Brain↗

PubMed1997

Pharmacokinetic analysis of octa-alpha-butyloxy-zinc phthalocyanine in mice bearing Lewis lung carcinoma.

OBJECTIVE: In this study, the pharmacokinetics of octa-alpha-butyloxy-zinc phthalocyanine (8-alpha-bo-ZnPc) was studied with regard to Lewis lung carcinoma in mice after intravenous administration of 7.8 mumole/kg body weight at different incubation intervals. SUMMARY BACKGROUND DATA: The newly synthesized potential photosensitizer 8-alpha-bo-ZnPc is characterized by a high absorption coefficient at the far red wavelength (735 nm) with a good singlet oxygen quantum yield. METHODS: After intravenous administration of 7.8 mumole/kg body weight in mice bearing Lewis lung carcinoma, the accumulated photosensitizer was chemically extracted (at incubation intervals of 2, 6, 12, 24, 48, and 168 hours) from selected tissues, and the concentrations were measured by absorption spectroscopy. RESULTS: The parenchymatous organs, liver, and spleen showed maximum 8-alpha-bo-ZnPc concentrations after 6 hours of incubation. An extensive uptake was detected in lung extracts taken at 6, 12, 24, and 48 hours. The malignant tissue did not accumulate high 8-alpha-bo-ZnPc during the entire investigation period. The photosensitizer extracted from muscle, representing normal tumor-surrounding tissue and skin, was even lower. CONCLUSIONS: Because of the extremely low accumulation rate of the tumor, 8-alpha-bo-ZnPc is suggested to be administered topically or in combination with a suitable carrier system in order to increase the photosensitizer concentration in the target tissue, as well as to decrease the loss of dye to other tissues.

Animals↗

PubMed1997

Different cortical activation patterns in blind and sighted humans during encoding and transformation of haptic images.

In this study, we investigated whether the occipital cortex of blind humans is activated during haptic perception and/or transformation of a haptic image. Slow event-related brain potentials were monitored from 18 electrodes in 12 sighted and 15 congenitally blind participants while they were engaged in a haptic mental rotation task. In both groups, slow negative shifts appeared over (a) the frontal cortex at the beginning of each processing episode, (b) the left-central to parietal cortex during encoding and maintaining of a haptic image, and (c) the central to parietal cortex during image transformation. A pronounced slow negative potential over the occipital cortex emerged only in the blind individuals and was time-locked to the processing epochs. Its amplitude increased with the amount of processing load. The slow wave effects observed in the blind individuals could indicate that occipital areas participate in specific, nonvisual functions or they could reflect a coactivation of these areas whenever the activation level of task-specific processing modules located elsewhere in the cortex is raised by nonspecific thalamocortical input.

Adult↗

PubMed1997

[Memory traces in EEG].

The paper gives a brief overview of five experimental approaches in which memory processes were studied by means of event-related brain potentials (ERPs). Some of the results were already published in English (Study 1), while others are new and will be reported in greater length as full paper elsewhere (Studies 2, 3, 4, and 5). Study 1 revealed that retrieval of information from episodic long-term memory is accompanied by a systematic slow negative potential. The topography of this slow wave depends on the quality of the reactivated information (spatial vs. verbal), and its amplitude reflects the difficulty of the retrieval process. In experiment 2 ERPs were recorded while subjects acquired either explicit or implicit knowledge about a sequential stimulus-response pattern. The data suggest that explicit learners who posses verbalizable knowledge about sequential dependencies have formed both perceptual and motor representations, while implicit learners have formed motor representations only. In study 3 fact retrieval in mental arithmetic was activated by a verification task. Incongruent solutions evoked an arithmetic N400-effect whose amplitude varied with the associative distance between an expected and an actually perceived solution to a multiplication problem. In study 4 ERPs were recorded during mental rotation tasks. A set of experiments revealed that mental rotation is always accompanied by a systematic negative variation over the parietal cortex. The amplitude of this "rotation specific negativity" increases with an increasing angular disparity between a perceived sign and its normal upright template. It was shown that this negativity is functionally distinct from a P300-complex which is often superimposed on it within the same latency window. Finally, study 5 examined ERPs in a sentence reading task in which grammatically legal but infrequent sentence constructions had to be processed. A left-anterior negativity was observed whenever an explicit case marker (the definite article in German) signalled a nominal phrase at a noncanonical position. The LAN phenomenon appears to be a manifestation of a syntax processor which performes a first-pass formal analysis of a sentence and which possibly allocates working memory resources whenever a word cannot be assigned immediately to an expected propositional role.

Brain↗

PubMed1996

Event-related potentials during auditory and somatosensory discrimination in sighted and blind human subjects.

The objective of the present study was to test if and to what extent phasic and tonic event-related potentials of the human EEG may reflect phenomena of cortical plasticity. In particular, it was tested if the occipital cortex of blind subjects participates in the processing of non-visual stimuli. To this end, 12 blind and 12 blindfolded sighted subjects were tested in an auditory and a somatosensory discrimination task with 2 levels of discrimination difficulty. Slow and fast event-related potentials were recorded from 18 scalp electrodes. In addition to the negative slow waves found in sighted subjects over frontal and central sites during auditory and somatosensory discrimination, a pronounced negative wave was revealed in the blind also over occipital brain areas. These negative shifts were time-locked to the train of stimuli which had to be monitored with sustained attention, i.e. they rised and resolved with the beginning and the end of a 20-s discrimination time epoch. The P300 complex, on the other hand, which is a slow positive deflection over the posterior part of the scalp and which follows rare and task-relevant events 200-800 ms after stimulus onset was significantly smaller at occipital electrodes in the blind than in the sighted subjects. Combined with neurophysiological and neuronanatomical evidence originating from studies with visually deprived animals, these data suggest that the occipital cortex of blind human subjects is coactivated whenever the system is engaged in a task which requires sustained attention and is less effectively inhibited at the end of a perceptual time epoch. In total, the data cast doubt on the hypothesis that the occipital cortex of blind subjects participates in modality-specific non-visual information processing.

Adult↗

PubMed1995

[Epidemiological characterization of a pestivirus isolate from a viremic pig out of a mixed pig-cattle herd].

A pestivirus isolated from a healthy pig out of a mixed pig-cattle holding was identified by use of monoclonal antibodies as a porcine virus related or identical to bovine viral diarrhoea (BVD) virus. About 7% of the pigs of this herd showed neutralizing antibodies (nab) against BVD and Border Disease (BD) virus and against the homologous porcine nonclassical swine fever (CSF) pestivirus isolate 10421/Han94. The nab titres against this virus were clearly higher than against CSF virus strain Alfort/187. Amongst the cattle kept in the farm no BVD viraemic animal was detected. About 13% of them showed nab to BVD virus with higher titres against the BVD virus strain NADL than against the porcine pestivirus virus isolate 10421/Han94. There was no of a BVD virus transmission from the cattle to the pigs within this herd. The problem of misinterpretation of non-CSF virus isolation from pigs is discussed. The necessity of identifying pestiviruses of porcine origin by use of species-specific monoclonal antibodies is stressed in order to prevent erroneous declarations of CSF outbreaks.

Animal Husbandry↗

PubMed1995

[Clinical experiences in the use of para-immunity inducers in cattle during animal exhibitions].

IBR positive cattle after vaccination with dead vaccine may excrete IBR/IPV (BHV-1) virus when facing a stress situation. On cattle exhibitions the share of such individuals may vary between 8 and 34%. Since 1988 in order to protect animals against infections IBR negative cattle and cows on 7 regional, one national and one international exhibitions were treated with Duphamun and Baypamun, respectively. After returning of animals to their owner IBR outbreaks were confirmed in 8 forms. This is low incidence compared with breeding exhibitions that where held in the same place or elsewhere. For protection against BHV-1 virus infection the use of a para-immunity-inducer is recommended. Nevertheless strict quarantine and following serological investigations are essential.

Adjuvants, Immunologic↗

PubMed1994

[Field infection with BVD virus in swine: epidemiology and diagnosis].

In a pig breeding herd in Lower Saxony infertility of breeding sows had been repeatedly observed. Growth retardation and post mortem findings in two piglets gave clinical indication to swine fever/hog cholera. A virus was isolated and typed by monoclonal antibodies as pestivirus not identical with hog cholera virus (HCV). In neutralization tests applying the field isolate, HCV and bovine viral diarrhea (BVD) virus the sera breeding sows and weaner pigs yielded high neutralizing antibody titres against the pestivirus field isolate but low titres against HCV. Specific antibodies against HCV were ruled out by a complex trapping blocking (CTB) ELISA. Intranasal inoculation of a weaner pig with spleen homogenate led to a short-termed viraemia without clinical signs but seroconversion with high antibody titres against the homologous pestivirus. In an in-contact pig no virus was detected and no antibody demonstrated within a period of 18 weeks.

Animals↗

PubMed1993

Topographic differences of slow event-related brain potentials in blind and sighted adult human subjects during haptic mental rotation.

Twelve blindfolded sighted, nine congenitally blind, and seven adventitiously blind subjects were tested in a haptic mental rotation task while slow event-related brain potentials in the EEG were recorded from 17 scalp locations. The overall topography of the slow wave pattern which prevailed during the task differed for sighted and for blind, but not for congenitally and adventitiously blind subjects. While the tactile stimuli were encoded, the blind showed a pronounced occipital and the sighted a pronounced frontal activation. The task-specific amplitude increment of a negative slow wave which can be understood as a manifestation of the process of mental rotation proper, showed a different topography for sighted and for blind subjects too. It had its maximum over central to parietal cortical areas in both groups, but it extended more towards occipital regions in the blind. In both groups, the effects were very similar to those observed in former studies with visual versions of the mental rotation task, i.e. the slow wave amplitude over central to parietal areas increased monotonously with an increasing angular disparity of the two stimuli to be compared. These results are discussed with respect to the question of whether visual deprivation in the blind can cause a reorganization of cortical representational maps.

Adult↗

PubMed1993

Synthesis and application of new microcarriers for animal cell culture. Part I: Design of polystyrene based microcarriers.

In this work (Part I), surface modified styrene polymers as new microcarrier material for animal cell culture were extensively investigated. The first synthesis steps--carried out by chloromethylation, sulphonation and nitration of the polystyrene matrix--resulted in precursors with a defined surface layer thickness. The obtained hydrophobic bulk phase showed a limited absorption of hydrophilic media components compared to polysaccharides matrices like dextran. By varying reaction conditions for microcarrier synthesis and/or by using similar styrene type polymer matrices like polyvinyltoluene, the specific density (1.028-1.05 g/cm3) of the microcarrier matrix was adjusted without problems. Chemical varying of the microcarrier surface by reaction of the precursors with different amines, saccharides or proteins led to new microcarriers with optimal conditions for cell adhesion and cell growth. All biological investigations were carried out with a BHK 21 (c-13) cell line. Detailed results will be discussed and summarized in Part II of this work.

Amines↗