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Biomedical subjects

W Gruber

Publications and source records attributed to W Gruber.

At least 19 recordsLinked to original sources
PubMed2005

Intelligence related upper alpha desynchronization in a semantic memory task.

Recent evidence shows that event-related (upper) alpha desynchronization (ERD) is related to cognitive performance. Several studies observed a positive, some a negative relationship. The latter finding, interpreted in terms of the neural efficiency hypothesis, suggests that good performance is associated with a more 'efficient', smaller extent of cortical activation. Other studies found that ERD increases with semantic processing demands and that this increase is larger for good performers. Studies supporting the neural efficiency hypothesis used tasks that do not specifically require semantic processing. Thus, we assume that the lack of semantic processing demands may at least in part be responsible for the reduced ERD. In the present study we measured ERD during a difficult verbal-semantic task. The findings demonstrate that during semantic processing, more intelligent (as compared to less intelligent) subjects exhibited a significantly larger upper alpha ERD over the left hemisphere. We conclude that more intelligent subjects exhibit a more extensive activation in a semantic processing system and suggest that divergent findings regarding the neural efficiency hypotheses are due to task specific differences in semantic processing demands.

Adolescent↗
PubMed2005

Oscillatory EEG correlates of episodic trace decay.

Recent studies suggest that human theta oscillations appear to be functionally associated with memory processes. It is less clear, however, to what type of memory sub-processes theta is related. Using a continuous word recognition task with different repetition lags, we investigate whether theta reflects the strength of an episodic memory trace or general processing demands, such as task difficulty. The results favor the episodic trace decay hypothesis and show that during the access of an episodic trace in a time window of approximately 200-400 ms, theta power decreases with increasing lag (between the first and second presentation of an item). LORETA source localization of this early theta lag effect indicates that parietal regions are involved in episodic trace processing, whereas right frontal regions may guide the process of retrieval. We conclude that episodic encoding can be characterized by two different stages: traces are first processed at parietal sites at approximately 300 ms, then further processing takes place in regions of the medial temporal lobe at approximately 500 ms. Only the first stage is related to theta, whereas the second is reflected by a slow wave with a frequency of approximately 2.5 Hz.

Adult↗
PubMed2002

The interplay between theta and alpha oscillations in the human electroencephalogram reflects the transfer of information between memory systems.

The exchange of information between the working and long-term memory system (WMS and LTMS) was investigated. We analyzed evoked theta and upper alpha desynchronization in a special memory task, designed to study the transfer of information between both memory systems. The results show that during attempts to retrieve information from the LTMS, evoked theta oscillations spread from anterior to posterior recording sites. When information actually is retrieved, the direction reverses and theta spreads to frontal sites. This time point--when direction reverses--varies between subjects to a large extent but is significantly correlated with memory performance and the onset of upper alpha desynchronization. We conclude that this phenomenon reflects the transfer of information between the WMS and LTMS

Adult↗
PubMed2002

Laser acupuncture in children and adolescents with exercise induced asthma.

BACKGROUND: Laser acupuncture, a painless technique, is a widely used alternative treatment method for childhood asthma, although its efficacy has not been proved in controlled clinical studies. METHODS: A double blind, placebo controlled, crossover study was performed to investigate the possible protective effect of a single laser acupuncture treatment on cold dry air hyperventilation induced bronchoconstriction in 44 children and adolescents of mean age 11.9 years (range 7.5-16.7) with exercise induced asthma. Laser acupuncture was performed on real and placebo points in random order on two consecutive days. Lung function was measured before laser acupuncture, immediately after laser acupuncture (just before cold dry air challenge (CACh)), and 3 and 15 minutes after CACh. CACh consisted of a 4 minute isocapnic hyperventilation of -10 degrees C absolute dry air. RESULTS: Comparison of real acupuncture with placebo acupuncture showed no significant differences in the mean maximum CACh induced decrease in forced expiratory volume in 1 second (27.2 (18.2)% v 23.8 (16.2)%) and maximal expiratory flow at 25% remaining vital capacity (51.6 (20.8)% v 44.4 (22.3)%). CONCLUSIONS: A single laser acupuncture treatment offers no protection against exercise induced bronchoconstriction in paediatric and adolescent patients.

Acupuncture Therapy↗
PubMed2001

Theta synchronization during episodic retrieval: neural correlates of conscious awareness.

The neural correlates of conscious awareness during successful memory retrieval were examined. In a recognition test, subjects indicated whether they consciously recalled the event in which a word was earlier presented (Remembering), or whether they recognized it on the basis that it was familiar in the absence of recollection (Knowing). An early EEG synchronization in the theta band predicted knowing, and a later remembering. Moreover, early and late event-related potentials were also found to predict knowing and remembering, respectively. The results indicate that the temporal dynamics of theta synchronization are related to the particular conscious experiences associated with memory retrieval.

Adult↗
PubMed2001

Alpha and beta band power changes in normal and dyslexic children.

OBJECTIVE: Previous research with healthy subjects suggests that the lower alpha band reflects attentional whereas the upper alpha band semantic processes. The aim of the present study was to investigate whether dyslexics show deficits in attentional control and/or semantic encoding. METHOD: The EEG was recorded while subjects were reading numbers, words and pseudowords and analyzed in a lower and upper alpha and two beta bands (spanning a range of about 8--16 Hz). A phasic response is measured in terms of a decrease in event related band power during reading with respect to a reference interval. Tonic power is measured in terms of (log) band power during a reference interval. RESULTS: In the lower alpha band dyslexics show an increased phasic response to words and pseudowords at right hemispheric sites but a lack to respond to words at O1. The upper alpha band exhibits a highly selective phasic response to words at left frontal sites but for controls only, whereas dyslexics show a general increase in tonic upper alpha power. Whereas the low frequency beta band (beta-1a) exhibits a rather diffuse pattern, a highly selective finding was obtained for the beta-1b band. CONCLUSIONS: Dyslexics have a lack of attentional control during the encoding of words at left occipital sites and a lack of a selective topographic activation pattern during the semantic encoding of words. Because only in controls reading of words is associated with a strong beta-1b desynchronization at those recording sites which correspond to Broca's area (FC5) and the angular gyrus (CP5, P3), we may conclude that this frequency band reflects the graphemicphonetic encoding of words.

Alpha Rhythm↗
PubMed2001

Theta band power changes in normal and dyslexic children.

OBJECTIVE: Tonic and phasic (event-related) theta band power changes were analyzed in a sample of 8 dyslexic and 8 control children. Previous research with healthy subjects suggests that electroencephalograph (EEG) theta activity reflects the encoding of new information into working memory. The aim of the present study was to investigate whether the processing deficits of dyslexics are related to a reduced phasic theta response during reading. METHOD: The EEG was recorded while subjects were reading numbers, words and pseudowords and analyzed in a lower and upper theta band (4--8 Hz). A phasic response is measured in terms of an increase in event related band power during reading with respect to a reference interval. Tonic power is measured in terms of (log) band power during a reference interval. RESULTS: Large group differences in tonic and phasic lower theta were found for occipital sites where dyslexics show a complete lack of pseudoword processing. For words, only controls show a highly selective left hemispheric processing advantage. CONCLUSIONS: Dyslexics have a lack to encode pseudowords in visual working memory with a concomitant lack of frontal processing selectivity. The upper theta band shows a different pattern of results which can be best interpreted to reflect the effort during the encoding process.

Child↗
PubMed2000

Traumatic brain stem lesions in children.

Glasgow Coma Scale (GCS) scores on admission may be predictors of outcome in patients with brain injuries. This study correlated the outcomes of children with traumatic brain stem lesions with their initial GCS scores and morphological patterns of injury as shown on computed tomography (CT) or magnetic resonance (MR) imaging. During the last 16 years, we have treated 1,108 children with brain injuries. The entire series included only 21 (1.9%) children who had clinical signs of brain stem lesions with morphological correlates on CT or MR imaging. Clinical findings were assessed according to the GCS and compared with scores on the Glasgow Outcome Scale (GOS). Of these 21 children, 16 (76%) had morphological lesions seen on CT scans. In 5 (24%) of the children only the MR images revealed brain stem lesions and their CT scans were negative. Generalized severe brain swelling was present in 6 cases (28%). There was a significant difference in GOS scores between patients with initial GCS scores of 3 and 4 and those with GCS scores between 5 and 7 (P < 0.02). Children with intracranial pressure higher than 40 mmHg had poorer outcomes than patients whose intracranial pressure was lower, but the differences were not significant. Outcome did not correlate significantly with morphological patterns of injury or the presence of extracranial injuries. The GCS is a reliable indicator of severity of injury and of outcome in children with brain stem injuries. MR imaging was more sensitive than CT in detecting brain stem lesions.

Adolescent↗
PubMed2000

Theta oscillations and the ERP old/new effect: independent phenomena?

OBJECTIVES: The hypothesis is examined whether a memory-related change in induced band power (oscillatory old/new effect) is functionally related to a memory-related increase in ERP positivity (ERP old/new effect). METHODS: In order to avoid a confounding on the measurement level, induced band power (IBP) was used as a measure that is devoid of the influence of evoked components. The EEG was recorded during a recognition memory task. RESULTS: The results show that compared to correctly rejected words, targets (remembered words) elicit a significantly larger P300. An oscillatory old/new effect was found for the delta and theta but not for the alpha band. It is manifested by an increase in delta and theta IBP which is significantly larger for targets than for correctly rejected words. It can be observed during the same time interval and shows the same topographic distribution as the ERP old/new effect. Most importantly, however, the ERP old/new effect (as well as the P300 itself) is generated by very slow frequencies which lie below the delta band. CONCLUSIONS: These findings demonstrate that the two types of old/new effects are functionally related. Possible physiological mechanisms underlying this relationship are discussed in terms of a threshold change in the cortex (generating the P300) that occurs during an increase in hippocampal theta activity (generating an increase in induced theta power).

Adult↗
PubMed2000

Assessment of bronchodilator responsiveness in infants with bronchiolitis. A comparison of the tidal and the raised volume rapid thoracoabdominal compression technique.

Whether bronchodilators should be used for the treatment of infants with bronchiolitis is subject to debate, partly because of the low sensitivity of the methods for assessing lung function changes in infants. In the present study, we compared the recently introduced raised volume (RVRTC) with the conventional end-tidal rapid thoracoabdominal compression (ETRTC) technique in infants with acute viral bronchiolitis. In 17 infants lung function was assessed by both methods, at baseline values and after salbutamol inhalation. Forced expiratory volumes (FEV(0.5), FEV(0.75), FEV(1.0)) were used for the quantification of RVRTC measurement, and maximal expiratory flow at functional residual capacity (Vmax (FRC)) for ETRTC measurements. A significant individual change was defined by a mean postbronchodilator value that differed from baseline value by more than twice the within-subject coefficient of variation (CV). Group mean intrasubject CVs ranged from 4.7% to 5.3% for FEV parameters; it was 14.0% for Vmax (FRC). For the group, post-bronchodilator measurements did not differ significantly from baseline measurements. For the majority of infants, however, the within-subject comparison of responses revealed substantial differences between both techniques; while no infant demonstrated a significant increase in Vmax (FRC), eight (47%) infants responded with significantly improved timed volumes. The RVRTC technique provides the investigator with a more sensitive diagnostic tool for documenting the effectiveness of therapeutic interventions on an individual basis. Furthermore, the findings of the present study provide a rationale for the application of bronchodilators in a subgroup of infants with acute bronchiolitis.

Administration, Inhalation↗
PubMed1999

Reproducibility of forced expiratory flow and volume measurements in infants with bronchiolitis.

The end-tidal rapid thoracoabdominal compression (ETRTC) technique is an established method for lung function testing in infancy. Previous work in healthy infants, however, has shown that measurements with the newly developed raised volume rapid thoracoabdominal compression (RVRTC) technique are more reproducible than those with the ETRTC technique. So far, reproducibility of the two techniques has not been compared in infants with acute airway disease. Twenty-three infants with acute viral bronchiolitis underwent lung function assessment with both the ETRTC and the RVRTC technique. A series of 8-10 measurements with each technique was done in randomized order. Forced expired volumes at 0.5, 0.75, and 1 sec after chest compression (FEV(0.5), FEV(0.75), and FEV(1.0)) were measured with the RVRTC technique; maximum expiratory flow at functional residual capacity (V'(maxFRC)) was measured with the ETRTC technique. Group mean intrasubject coefficients of variation (CV) were 4.84% for FEV(0.5), 5.01% for FEV(0.75), 5.43% for FEV(1. 0), and 13.79% for V'(maxFRC), respectively. Differences between FEV parameters were statistically insignificant, whereas the difference between each FEV parameter and V'(maxFRC) was highly significant (P < 0.001). In infants with acute viral bronchiolitis, RVRTC measurements have significantly less intraindividual variability than flow rates assessed with the conventional ETRTC technique. This finding provides the basis for assessing disease course and effects of therapeutic interventions on an individual basis.

Analysis of Variance↗
PubMed1999

Effect of specific immunotherapy with house dust mite extract on the bronchial responsiveness of paediatric asthma patients.

BACKGROUND AND OBJECTIVE: Allergic asthma is common in children, and house dust mite (HDM) is an important source of perennial allergens. Bronchial hyperresponsiveness is a functional hallmark of asthma. Specific immunotherapy (SIT) with HDM extracts were shown to decrease symptoms, but its effect on bronchial responsiveness, as measured by non-pharmacological challenges, has not been evaluated. METHODS: Twenty-six paediatric asthma patients allergic to HDM participated in this study. Fourteen patients received SIT with a HDM extract (Alavac, Bencard) for 2 years, and 12 served as controls. Bronchial responsiveness was assessed non-pharmacologically by cold dry air challenge (CACh) before and 3, 6, 12 and 24 months after SIT, and 12 months after termination of SIT. RESULTS: After 24 months, the SIT group showed a statistically significant reduction of the mean CACh-induced changes of both forced expiratory volume in one second (-21.8+/-2.7% vs. -13.7+/-2.4%; P = 0.03) and maximal expiratory flow at 25% remaining vital capacity (-48.9+/-4.9% vs. -27.9+/-6.2%; P = 0.01). In contrast, no significant changes of bronchial responsiveness were observed in the control group. In the SIT group more patients lost their bronchial hyperresponsiveness than in the control group (6/14 vs. 1/12; P<0.05). One year after terminating SIT, the treatment group showed a tendency towards returning bronchial hyperresponsiveness. CONCLUSION: These results demonstrate that during 2 years of SIT there was a reduction of bronchial hyperresponsiveness in HDM-allergic paediatric asthma patients.

Adolescent↗
PubMed1999

Serum eosinophil cationic protein and bronchial responsiveness in pediatric and adolescent asthma patients.

BACKGROUND: Serum eosinophil cationic protein (ECP) has been promoted as a marker of inflammatory activity in bronchial asthma. Bronchial responsiveness, measured either by inhaling pharmacologically active substances such as histamine or methacholine, or by applying physical stimuli such as the hyperventilation of cold dry air, is also considered to be an indirect marker of bronchial inflammation. OBJECTIVES: In this study, we investigated the possible relationship between serum ECP and bronchial responsiveness to both cold dry air and histamine in presently symptom- and medication-free pediatric and adolescent asthma patients. SUBJECTS: Thirty-six children and adolescents with atopic asthma were studied. METHODS: On 2 consecutive days, bronchial responsiveness was assessed nonpharmacologically by cold dry air and pharmacologically by histamine in random order. Blood samples for determination of ECP were collected before each challenge. RESULTS: Serum ECP levels correlated with neither cold dry air-induced changes in FEV1 nor the provocation concentrations of histamine causing a 20% fall in FEV1. Subjects with bronchial hyperresponsiveness to cold dry air and histamine had somewhat higher levels of serum ECP than subjects with normal responses, but these differences were insignificant. CONCLUSIONS: Our results indicate a lack of relationship both between serum ECP and bronchial responsiveness to cold dry air and between serum ECP and bronchial responsiveness to histamine.

Adolescent↗
PubMed1998

Association between female sex hormones and biochemical markers of bone turnover in peri- and postmenopausal women.

In an epidemiological study, markers of bone formation (serum osteocalcin and C-terminal propeptide of type I collagen) and bone resorption [urinary type I collagen peptides (Crosslaps), urinary total pyridinoline (TPYRI), urinary deoxypyridinoline (DPYRI) as well as female sex hormones (serum estradiol)], follicle-stimulating hormone (FSH) and luteinizing hormone were measured in 237 women. This cohort aged 44-66 years, came for their first medical examination since menopause to the outpatient menopause clinic at the Kaiser-Franz-Josef-Hospital, Vienna. The women were all 0.5-5.0 years since cessation of menses and were not taking medications other than hormone replacement therapy [52 cases, 21.9%)] and had no diseases known to affect bone and mineral metabolism. The best correlation was found between urinary DPYRI and urinary TPYRI (r = 0. 63, P = 0.0001), followed by urinary Crosslaps and urinary DPYRI (r = 0.47, p = 0.0001). Only weak but significant correlations between E2 and urinary Crosslaps (r = -0.21, P < 0.0001) as well as serum E2 and serum osteocalcin (r = -0.16, P = 0.0007), were observed. Of the 237 women 53% suffered from a severe E2 deficiency (E2 < 10.0 ng/liter). In these patients, urinary Crosslaps (+48%) and serum osteocalcin (+22%) were significantly higher (P < 0.0001) compared with those patients with E2 levels > 10 ng/liter. Women with E2 levels >10 ng/liter were further subdivided into those with and without sex hormone replacement therapy, whereby no statistical differences in any of the biochemical markers could be observed between these groups. We could clearly demonstrate that in postmenopausal women suffering from severe E2 deficiency (E2 < 10 ng/liter), urinary Crosslaps and serum osteocalcin are significantly increased, indicating in principle a clear correlation between E2 deficiency and these markers of bone turnover.

Adult↗
PubMed1997

Complications after shunting isolated IV ventricles.

An isolated IV ventricle in chronically shunted patients is being reported with increasing frequency. Complications associated with posterior fossa shunting, however, have seldom been described. Between January 1986 and December 1995, we treated 292 children younger than 16 years for hydrocephalus: 7 (2.4%) developed an isolated IV ventricle, and 5 of these were symptomatic with posterior fossa signs. These 5 patients required posterior fossa shunting, after which their neurological status improved. However, 1 week and 6 weeks after surgery, respectively, 2 patients developed new cranial nerve deficits related to a slit-like IV ventricle with secondary irritation of the brain stem by the IV ventricular catheter. Shortening the catheter and replacing the valve eliminated the cranial nerve palsies, implying that these complications were not caused by direct injury of the brain stem during placement of the shunt. Alternative surgical techniques and the use of different (flow-regulating) valves may avoid such complications.

Adolescent↗
PubMed1997

Ganciclovir treatment of symptomatic congenital cytomegalovirus infection: results of a phase II study. National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group.

Congenital cytomegalovirus (CMV) infection occurs in approximately 1% of newborns in the United States. A phase II evaluation was done of ganciclovir for the treatment of symptomatic congenital CMV infection. Daily doses of 8 or 12 mg/kg were administered in divided doses at 12-h intervals for 6 weeks. Clinical and laboratory evaluations sought evidence of toxicity, quantitative virologic responses in urine, plasma drug concentrations, and clinical outcome. A total of 14 and 28 babies received 8 and 12 mg/kg/day, respectively. Five additional babies received ganciclovir on a compassionate plea basis. Significant laboratory abnormalities included thrombocytopenia (< or = 50,000/mm3) in 37 babies and absolute neutropenia (< or = 500 mm3) in 29 babies. Quantitative excretion of CMV in the urine decreased; however, after cessation of therapy, viruria returned to near pretreatment levels. Hearing improvement or stabilization occurred in 5 (16%) of 30 babies at 6 months or later, indicating efficacy.

Alanine Transaminase↗
PubMed1997

The effect of multidimensional exercises on balance, mobility, and fall risk in community-dwelling older adults.

BACKGROUND AND PURPOSE: This prospective clinical investigation examined the effects of a multidimensional exercise program on balance, mobility, and risk for falls in community-dwelling older adults with a history of falling. Factors used to predict adherence and a successful response to exercise were identified. SUBJECTS: A total of 105 community-dwelling older adults (> or = 65 years of age) with a history of two or more falls in the previous 6 months (no neurologic diagnosis) participated. They were classified into (1) a control group of fallers (n = 21), (2) a fully adherent exercise group (n = 52), and (3) a partially adherent exercise group (n = 32). METHODS: Following evaluation, each patient received an individualized exercise program addressing the impairments and functional disabilities identified during the assessment. The control group received no intervention. Changes in performance on five clinical tests of balance and mobility and fall risk were compared among groups. RESULTS: Both exercise groups scored better than the control group on all measures of balance and mobility. Although both exercise groups showed a reduction in fall risk compared with the control group, the greatest reduction was found in the fully adherent exercise group. Factors associated with successful response to exercise included degree of adherence to exercise program and pretest score on the Tinetti Mobility Assessment. CONCLUSION AND DISCUSSION: Exercise can improve balance and mobility function and reduce the likelihood for falls among community-dwelling older adults with a history of falling. The amount of exercise needed to achieve these results, however, could not be determined from this study.

Accidental Falls↗