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L Balázs

Publications and source records attributed to L Balázs.

At least 19 recordsLinked to original sources
PubMed2002

Fourier transform infrared analysis of gas composition in low-volume light bulbs.

Fourier transform infrared spectroscopy has been used for in situ analysis of HBr, CH3Br, and CO within light bulbs at different stages of burning time. The interference fringes originated in the quartz walls of the bulbs have been eliminated by different methods. The NIPALS procedure yielded higher S/N ratio than the fringe-elimination method applied. The CO and HBr showed time-dependent concentration changes during the burning period. The maximum CO concentration (approximately 6 ppm) was detected after 30-50 s of burning time, and then it practically burned out after 5 h. The HBr concentration increased in the first 3 min of burning, and then its concentration stabilized at a 10-15 ppm level. After 5 s of illumination, the CH3Br concentration became undetectable.

Journal Article↗
PubMed2001

Event-related potentials and audiovisual stimuli: multimodal interactions.

In a discrimination task event-related potentials (ERPs) were recorded in human participants to simultaneously presented visual and auditory stimuli with relevant and irrelevant auditory and visual features. Stimuli consisted of combinations of a sine-wave tone (either target or non-target frequency) and a rectangle of particular (target or non-target) orientation. In two conditions either the auditory or the visual discrimination was easier. Stimuli with just one target feature elicited attention-related ERP components (selection negativity and N2b in the visual, and N2b in the auditory modality) only if that feature could be easily discriminated. This finding shows the hierarchical organization of attentional processing of auditory and visual features. Target stimuli in both conditions elicited visual and auditory attention-related components. This finding, together with the similarity of ERPs to stimuli without target features suggest, that these components cannot be considered as on-line correlates of elementary discrimination processes.

Acoustic Stimulation↗
PubMed1999

Effects of cue information on response production and inhibition measured by event-related potentials.

The aim of this study was to investigate how information carried by a cue stimulus modulate event-related potentials (ERPs) to a subsequent target stimulus which either calls for an overt response (Go stimulus) or no response (Nogo stimulus). One of the cues predicted the likely appearance of the Go stimulus (Go cue) whereas the other cue predicted the likely appearance of the Nogo stimulus (Nogo cue). Our results showed that unpredicted Nogo stimuli elicited enlarged N200 component. This finding supports the notion that Nogo N200 reflects response inhibition processes, i.e., the amplitude of the N200 is a function of the difficulty of response inhibition. In other words, increased N200 to Nogo stimuli following Go cues might be related to increased efforts in activating the response inhibition system thereby interrupting preparations to respond.

Adolescent↗
PubMed1998

Object-related attention: an event-related potential study.

In two experiments reaction time (RT) and event-related potentials (ERPs) were measured to visual stimuli consisting of two objects (Duncan, 1984; Vecera & Farah, 1994). Target stimuli were defined by two features, which either were distributed between the two objects or belonged to a single object. In Experiment 1 the two objects appeared in spatial overlap, whereas in Experiment 2 the two objects were spatially separated. In both experiments RT was shorter in the single-object condition. The late positive component of the ERP (P3) emerged, peaked, and declined earlier in the single-object condition. It is suggested that object-related attention may facilitate the earlier onset of search for the relevant features.

Adult↗
PubMed1998

Responses to irrelevant probes during task-induced negative and positive shifts.

The functional significance of task-induced negative and positive cortical shifts were tested with the probe-stimulus method. Both shifts were induced within the same experimental situation in three variants of a CNV paradigm, where a slow positive wave (a variant of P300) appeared following S2. In Experiment I and II, S2 called for making or withholding a motor response (go/no-go); in Experiment III, S2 informed the subject about the correctness of a previous guess. Irrelevant probe-stimuli were applied in conjunction with the task during the CNV, the post-S2 positivity and the intertrial interval (ITI). The probe-evoked vertex EPs were smaller during the post-S2 positivity as compared to the CNV and the ITI. This was true not only for the motor task but also for the guessing task, where the effect is unlikely to have been contaminated by motor potentials. This indicates that positive shifts have an inhibitory effect on the processing of irrelevant probe-stimuli and possibly on information-processing in general.

Adolescent↗
PubMed1998

Attention to features of separate objects: an ERP study of target-shooters and control participants.

In a visual discrimination task stimuli consisted of a color circle and a grating pattern, i.e. target features were distributed between two objects. The relation (hierarchical vs. parallel) between the attentional processing of the task-related features (color and spatial frequency) was investigated by using the methods of event-related potentials (ERPs). Participants with considerable practice in visual attention (target shooters; n = 13) were compared to control subjects (n = 11). Attention-related ERP components, i.e. selection (anterior) positivity (SP), selection negativity (SN), N2 (N2b), furthermore the late positivity (P3b) emerged only if the circle had relevant color. These results suggest preponderance of color processing. Target shooters were faster and more accurate than the control group. Attention-related components (SP, N2b) and the late positivity (P3b) were larger in shooters, but the relations among the attention-related components were the same in two groups, showing similar progression of the target selection process.

Adolescent↗
PubMed1994

The effect of monocular viewing on heartbeat discrimination.

In monocular viewing conditions, an activational imbalance between the cerebral hemispheres was assumed to develop, the direction of which depends on the side of the viewing eye. This assumption was based on the morphological differences between the nasal and the temporal hemiretinas and on physiological data. It was assumed that the hemisphere receiving visual information via the nasal optic fibers, that is, the hemisphere contralateral to the viewing eye, would be the more activated one. Because heartbeat perception is regarded as a predominantly right hemispheric function, it was predicted that during right hemispheric activation created by left monocular viewing heartbeat discrimination performance would be better than during left hemispheric activation created by right monocular viewing. This hypothesis was tested on 30 male right-handed university students who performed a Whitehead-type heartbeat discrimination task while viewing only with the left or with the right eye. Heartbeat perception was more accurate when viewing with the left eye. Additionally, respiratory manipulation during heartbeat discrimination improved performance on this task.

Adult↗
PubMed1992

Computer determination of systolic time intervals based on impedance cardiography.

A computerized system has been developed based on impedance cardiography for processing systolic time intervals (STI) in psychophysiological experiments. The conventional method of STI determination is based on transducing three signals: electrocardiogram, phonocardiogram and pulse tracing (carotid pulse). Because of its negligible pulse transmission time the first derivative impedance cardiogram (dZ/dt) is more reliable than other pulse signals. Since the sharply demarcated points of the dZ/dt waveform occur simultaneously with the cardiac events the dZ/dt makes phonocardiogram processing unnecessary. Computer algorithms for STI assessment are based on processing two signals: the ECG and dZ/dt. The pre-ejection period (PEP), the left ventricular ejection time (LVET) and electromechanical systole (QS2) are derived by recognizing the B and X points on the dZ/dt signal as the endpoints of PEP and LVET respectively. X point identification consists of two steps: (i) the estimation of the QS2 based on the regression relationship between QS2 and heart rate (HR) and (ii) a filtering procedure for exact localization of the X point. The B point is determined by calculating the curvature function of the dZ/dt and employing a clustering procedure. The accuracy and reliability of the software were tested by processing data from 40 subjects under stress condition (cold pressor and mental arithmetic).

Algorithms↗
PubMed1990

Hemispheric preference and obesity.

This study investigated the relationship of hemispheric preference--the tendency to activate one hemisphere rather than the other--and obesity, on 37 right-handed, male university students. Hemispheric preference was assessed by the directionality of conjugate lateral eye movements, and the degree of obesity was determined by the body mass index (BMI). The results showed that right hemisphere preferent subjects ("left-movers") are less obese than left hemisphere preferents ("right-movers").

Adolescent↗
PubMed1990

The effect of lateral visual fixation and the direction of eye movements on heartbeat discrimination.

This study was undertaken to determine whether the asymmetrical activation of the two cerebral hemispheres affects the accuracy of heartbeat perception. Hemispheric preference--the tendency to activate one hemisphere rather than the other--was assessed by the directionality of conjugate lateral eye movements. Actual differential hemispheric activation was achieved by contralateral visual fixation. The results of 44 right-handed male subjects showed that right hemisphere preferent subjects ("left-movers") performed better on a heartbeat discrimination task than left hemisphere preferent subjects ("right-movers"). The direction of lateral visual fixation also influenced heartbeat discrimination: subjects fixating to the left were more accurate than those fixating to the right.

Adolescent↗
PubMed1990

Detection of colon distension in colonostomy patients.

Inborn and learned ability to detect mild, nonpainful distension of the sygmoid colon was examined in 22 patients who underwent colonostomy one year or more before the investigation. The colon was distended by a balloon inserted 10 cm below the orifice of the artificial anus. Each subject participated in three sessions on three consecutive weeks with several experimental tasks in each session. During each task, the patient received the colon stimulus (the "signal") 25 times randomly paired with masking auditory or annular skin stimuli (around the stoma or 15 cm medially to it). The masking (warning) stimuli were administered in series of 50, representing the "noise," according to signal-detection paradigms. The subjects had to indicate after each administration of the warning noise stimulus whether or not they thought the colon stimulus had been presented. In all three sessions, learning tasks were included using reinforcement of successful detection trials. Seven subjects out of 22 were considered good perceivers, 9 persons were considered medium perceivers, and the remaining 6 subjects were considered poor perceivers. According to the data of the first two groups, it can be hypothesized that most patients have some inherent sensitivity of colon distension, and that learning improves this initial ability. However, the role of skin, peritoneal, or interstitial receptors in colon distension detection cannot be excluded.

Adult↗
PubMed1990

[The incidence of Hodgkin's disease: characteristics of its appearance, histological types].

In study of lymphogranulomatosis (LGM), epidemiological surveys and so-called "Rye Classification" for separation of histological types significantly helped to get to know the background and circumscription of etiopathogenesis of the disease. In her paper author analysed histological distribution of types, distribution of sex of patients, their average age, age-specific incidence of disease in LGM registered cases of ten years in Malignant Lymphoma Reference Centre. On basis of rate of histological types, compared to each other, and of number of LGM cases in childhood, it can be established that in MLRC incidence of LGM corresponded to so-called intermediary types (II), namely it showed characteristics of distribution between developed and economically underdeveloped countries. Age-specific incidence of 716 LGM cases studied by author was ot bimodal character, age-specific incidence of nodular sclerosis was different from it. Presumably this fact and different nature of LGMs of other type or its different pathogenesis are in the background.

Hodgkin Disease↗
PubMed1990

[Immunohistology of Hodgkin's disease. Use of monoclonal antibodies in the analysis of the pathomorphology of Hodgkin's disease].

Author studied cryostatic sections of lymph node biopsy of 45 untreated patients suffering in lymphogranulomatosis by known T and B lymphocyte, macrophage-histiocyte, Ia and HLA-DR and transferrine receptor specific monoclonal antibodies (moats). In HK-LP, HK-NS, HK-MC and HK-LD the infiltrations were formed by phenotyped lymphocytes contrary to HK-NP, where HK nodules were composed of B-cells. In HK-LPs T lymphocytes were of T-helper phenotypes, and these T-cells were observed in cases of HH-NS and HK-MC, abounding in lymphocytes, besides a few T-suppressor cells. The number of lymphocyte of latter type increased in HK-NS and and HK-MC, poor in lymphocytes and in HK-LD. The giant cells had positive reaction with Leu3a, Leu5, OKIa, HLA-DR and transferrine receptor specific moats. SR cells are such anaplasic cells or probably tumorous cells developed by cell hybridization, which are able to antigen expression characteristic of various hemopoietic cell line and of activated cells, respectively.

Antibodies, Monoclonal↗
PubMed1987

Lymphocyte subpopulations and immunoglobulins in idiopathic thrombocytopenic purpura (ITP).

Data gained from observations of the humoral and cellular immunity of 22 patients with ITP (11 in remission and 11 splenectomised) are presented. The amount of T-lymphocytes according to E-rosetting decreased significantly. In tests performed with monoclonal sera the amount of OKT-4 cells was significantly lower then normal, and the ratio of OKT-4/OKT-8 was also reduced. The C-4 complement fraction showed a significant reduction, and a rise was observed in the three Ig classes. No differences could be found, however, between patients in remission and in relapse, and between the splenectomised cases, those treated with prednisolone, and those who had no such treatment. Apart from the primary role of antiplatelet antibodies that cause thrombopenia, a complex disturbance in immune regulation also occurred in ITP, and this manifested with changes in the T-lymphocyte subpopulations. Its pathological progress still remains to be justified, but the plasma of healthy individuals and gammaglobulin have a favorable effect by blocking their receptors and they result in the cessation of the symptom and thrombocytopenia.

Adult↗