Biomedical subjects

E Marosi

Publications and source records attributed to E Marosi.

At least 19 recordsLinked to original sources

PubMed2001

Delayed P300 during Sternberg and color discrimination tasks in poor readers.

The P300 ERP component was studied in poor and normal readers, using Sternberg and color discrimination (Spaceships) tasks. During the first one, subjects must decide if a probe item belongs or not to a set of digits previously presented. In the second one, the participants must shoot violet spaceships with one key and other than violet spaceships with another key. There were no significant differences between groups with respect to reaction times, but a larger proportion of errors was observed in poor readers. Longer P300 latencies were recorded for poor readers than controls in both tasks. P300 amplitudes showed topographical differences between the two groups: Poor readers' P300 is larger frontally during the Sternberg task, but smaller at posterior sites during the Spaceships task. These results suggest that poor readers may have deficiencies during the early processing stage, such as visual stimulus evaluation. Poor readers also appear to have deficits for classifying and memorizing visual stimuli.

Child↗

PubMed2001

Broad band spectral measurements of EEG during emotional tasks.

Broad band spectral measurements were calculated on EEG recordings of 40 healthy male university students during emotional tasks using the emotion induction technique. Emotional stimuli were sentences with positive valence (joy of love), with negative valence (frustration) and neutral situation. Broad band measurements showed that delta and beta bands reflected better the differences by emotional state. Hemispheric differences associated to emotional states were obtained only for mean frequency data. Higher delta frequencies at left frontopolar, right frontal, parietal and temporal and higher beta frequencies at left frontotemporal and temporal were related to love. Meanwhile higher delta frequencies especially at left frontopolar and temporal regions and lower beta frequencies at midline frontal (Fz) and central (Cz) leads were associated to frustration. These findings suggest that narrow band measurements may reflect more efficiently EEG changes during emotional tasks.

Adult↗

PubMed2000

Specific EEG frequencies at specific brain areas and performance.

In this study it was shown that in adults, the frequency characteristics of EEG preceding stimuli that were followed by incorrect responses were different from the characteristics of EEG preceding stimuli that were followed by correct responses. In the recording during three different tasks that explore different neuronal networks, higher values of current preceding incorrect performance in those areas directly related to the task were found in frequencies within the delta (1.56 and 3.12 Hz) and beta bands (13.26, 14.04, 14.82, 15.6, 17.16 and 17.94 Hz), suggesting that these frequencies signal inhibition. Frequencies within the alpha band (9.36 and 12.48 Hz) showed greater energy preceding correct responses in task-specific areas, supporting previous results observed in children.

Adult↗

PubMed2000

Auditory event-related potentials in poor readers.

Although poor readers (PR) are considered the major group among reading-disabled children, there are not event-related potentials (ERP) studies reported of PR on the subject. In this study, attentional and memory processes were studied in an auditory oddball task in PR and normal controls. ERP to auditory stimuli were recorded in 19 leads of the 10/20 system, using linked earlobes as references, in 20 normal children (10 female) and 20 PR (10 female) of the same age (10-12 years old). Two pure tones (1000 and 3000 Hz) were used in an oddball paradigm. No significant differences were observed in the amplitudes and latencies of N100 between the groups. However, N200 to frequent stimuli and P200 to both frequent and infrequent stimuli were of higher amplitude in poor readers than in normal children. There were no differences between groups in the latency and amplitude of P300. The results suggest that PR use more attentional resources in the components occurring before P300 to both frequent and infrequent stimuli than the normal children, and this finding is particularly marked for PR girls.

Child↗

PubMed2000

Primary task demands modulate P3a amplitude.

Auditory event-related brain potentials (ERPs) were recorded from 10 subjects in two different conditions: (1) subjects were required to reorder five visually presented letters in order to form a word and provide a verbal response (task condition); (2) subjects were presented with a control stimulus with the same physical characteristics as the experimental stimulus, but containing just one type of letter (i.e., AAAAA). Subjects had to verbally respond to such stimuli by saying "A" (control condition). Tones of 1000 Hz (standard) and 1050 Hz (deviant) were also presented to the subjects in a 85%-15% probability paradigm 2 s before, during and 8 s after the presentation of the visual stimuli. Recordings were obtained from Fpz, Fz, Cz and Pz vs. linked ears. Auditory ERPs to the auditory stimuli after the presentation of the visual letter string and during the performance of the task were averaged for the standard and deviant tones in both conditions. Only correct responses were considered for the averages. The N100 was affected by stimulus type (standard vs. deviant) but not by condition (task vs. control); however, larger P3a waves were observed during the control than during the task condition. No significant differences between conditions were observed in the mismatch negativity (MMN) latency range. These results suggest that primary task demands modulate involuntary attention processing.

Acoustic Stimulation↗

PubMed1999

N400 and lexical decisions: automatic or controlled processing?

OBJECTIVE: To investigate whether the N400 effect is sensitive to automatic or controlled processes. METHODS: Two experiments were performed. In one experiment, directly related word pairs were used. In the other experiment, mediated-related word pairs were used. In order to reduce controlled processes, each experiment consisted of 3 tasks: Low- and high-proportion of related pairs, and single presentation lexical decision task. RESULTS: In the first experiment, the amount of priming was equivalent for the 3 tasks. The N400 effect appeared in the high and low proportion of directly related words, but not in the single presentation task. In the second experiment, behavioral priming was also found in the 3 tasks. However, the N400 effect was observed only in the task with low proportion of related pairs. CONCLUSION: These results suggest that the N400 effect may be related to controlled processes.

Adult↗

PubMed1999

Sources of abnormal EEG activity in the presence of brain lesions.

In routine clinical EEG, a common origin is assumed for delta and theta rhythms produced by brain lesions. In previous papers, we have provided some experimental support, based on High Resolution qEEG and dipole fitting in the frequency domain, for the hypothesis that delta and theta spectral power have independent origins related to lesion and edema respectively. This paper describes the results obtained with Frequency Domain VARETA (FD-VARETA) in a group of 13 patients with cortical space-occupying lesions, in order to: 1) Test the accuracy of FD-VARETA for the localization of brain lesions, and 2) To provide further support for the independent origin of delta and theta components. FD VARETA is a distributed inverse solution, constrained by the Montreal Neurological Institute probabilistic atlas that estimates the spectra of EEG sources. In all patients, logarithmic transformed source spectra were compared with age-matched normative values, defining the Z source spectrum. Maximum Z values were found in 10 patients within the delta band (1.56 to 3.12 Hz); the spatial extent of these sources in the atlas corresponded with the location of the tumors in the CT. In 2 patients with small metastases and large volumes of edema and in a patient showing only edema, maximum Z values were found between 4.29 and 5.12 Hz. The spatial extent of the sources at these frequencies was within the volume of the edema in the CT. These results provided strong support to the hypothesis that both delta and theta abnormal EEG activities are the counterparts of two different pathophysiological processes.

Brain Edema↗

PubMed1999

Broad band spectral EEG parameters correlated with different IQ measurements.

The relationship of IQ (measured by WAIS and all its subscales) and EEG broad band spectral parameters were studied in 40 right-handed, male volunteers ranging in age from 20 to 25 years old. EEGs were recorded in 20 derivations during rest with eyes opened. The results obtained reveal positive and negative correlations with abundant frontal participation in all bands. Mean frequency data show a frequency shift in a very narrow range suggesting that more relations in narrow band could be achieved. These results highlight the need of psychological tests that measure more homogeneous abilities and finer measurement technique to reveal clearly explainable correlations and demonstrate that EEG recordings do reflect intellectual abilities.

Adult↗

PubMed1998

Relationship of specific EEG frequencies at specific brain areas with performance.

This study shows that incorrect responses are preceded by different EEG characteristics than correct responses, and that these differences appear in specific brain regions that participate in each particular task. EEGs were recorded in children during three different tasks: color discrimination (CDT), verbal working memory (VWM), and word categorization task (WCT). EEG segments previous to the presentation of the stimulus were analysed. Incorrect responses were preceded by lower EEG power values at 7.8 Hz in posterior temporal and right parietal leads in CDT, 8.59 and 9.36 Hz in frontal areas in VWM, and 10.72 Hz in the left hemisphere in WCT. In the former task > 1.56 Hz power in frontal areas prior to an incorrect response was also observed.

Alpha Rhythm↗

PubMed1997

[Treatment of pancreatic insufficiency with a preparation containing high lipase activity].

In vitro testing of lipase survival of Panzytrat 25,000 homogenized in Tris HCl buffer and Lundh meal stimulated gastric or duodenal contents demonstrated favorable stability of lipase of this new preparation in the protein and fat containing gastric and duodenal juices of patients with chronic pancreatitis. Later an open, intra-individually controlled study with two doses of Panzytrat 25000 (5 x 1 and 5 x 2 capsules/day) was performed in 10 patients with severe pancreatic steatorrhoea. A diet containing 70 g of fat/day was offered and the 3-day fat loss of collected stools was measured in the last 3 days of 5-day equilibration periods with and without replacement therapy. After these short-term periods, patients were treated with 5 x 1 capsules of the drug for one month and body weight increases as well as patient's appraisals were registered. Stool weight and fat loss maximally decreased already in response to the 5-day treatment with 5 x 1 capsules of drug and double dose of the preparation did not further decrease steatorrhoea in most cases except 2 patient. Disappearance of fat loss was achieved in 3 out of ten patients. Body weight of patients increased in most cases and their subjective evaluation was also favorable.

Adult↗

PubMed1997

Evolution of cerebral edema and its relationship with power in the theta band.

In previous papers we have proposed that in patients with space-occupying lesions, delta power was related with the volume of the lesion and theta power with the volume of the edema. In this report we analyze the evolution of 10 patients with space-occupying lesions in whom we measured the volume of the lesion and of the edema before and after treatment that produced changes in these volumes. EEGs were recorded in the leads of the 10-20 system referenced to linked earlobes. Delta and theta powers were calculated for voltage and current source densities (CSD) and compared with age-norms to compute conventional Z-maps. These maps provide probability statements about the deviation of observed values from the norm. Rank correlations between the change in the volume of the lesion before and after treatment and the change in Z-values before and after treatment were significant only in the delta band. However, rank correlations between the change in the volume of the edema and the change in EEG Z-values were only significant in the theta band. These correlations were higher for CSD than for voltage estimates. We also observed that the site of the lesion and of the edema was better represented by CSD maps than by voltage maps. These results are also in agreement with our previous reports, in which we observed more precise localization of brain lesions by CSD than by voltage estimates.

Adult↗

PubMed1997

A follow-up study of EEG coherences in children with different pedagogical evaluations.

A follow-up study on EEG coherence values was carried out with 46 school-age children divided into three pedagogical groups considering their reading and writing abilities (normal subject and children with mild and with serious reading-writing problems). EEGs were recorded at rest, with eyes closed in 15 referential derivations that gave 105 possible coherence values. Coherence was calculated after the elimination of the average reference. Repeated Measure ANOVAs were calculated to evaluate the effects of time, sex, reading-writing problems and their interactions. The second EEG recordings were taken 2-3 years after the first. The results revealed significant increase of coherence values during the time lapse studied, consisting of an increase of frontal coherences in all bands, with the exception of the theta band. The most numerous changes occurred in the alpha band. Very few differences in coherence values were observed between the two EEG recordings by pedagogical groups and by sex suggesting a similar but not igual maturation of coherences of boys and girls and of the three pedagogical groups, in this age range studied. These findings suggests an abnormal coherence development for the reading disabled group, as well as different coherence maturation for boys and girls in this time lapse studied.

Child↗

PubMed1996

EEG delta activity: an indicator of attention to internal processing during performance of mental tasks.

In previous papers we proposed that an increase in delta EEG activity during mental tasks might be related to an increase in subjects' attention to internal processing. In this paper we have made a narrow band analysis to detect those EEG frequencies that change selectively during the performance of a mental task that requires attention to internal processing. Two different experiments were performed: (1) a difficult mental calculation task and a control stimulus with the same physical characteristics as the arithmetical symbols were presented in random order; (2) the Sternberg paradigm for the analysis of short term memory using a memory set of 5 or 3 digits was also presented in random order. Referential recordings to linked ears were obtained in all leads of the 10/20 system. In the first experiment, the increase of power from 1.56 to 5.46 Hz was observed only during the performance of the task and not during the control condition. In the Sternberg paradigm, the increase of power from 1.56 to 3.90 Hz was greater during the difficult than during the easy condition. These results support our hypothesis that an increase in delta activity may be related to attention to internal processing during the performance of a mental task.

Adult↗

PubMed1996

Biphasic effect of prostaglandin E1 on the severity of acute pancreatitis induced by a closed duodenal loop in rats.

The effect of prostaglandin E1 (PGE1) on the severity of acute pancreatitis induced by a closed duodenal loop in the rat was tested. PGE1 was administered subcutaneously at various doses (3, 6, 12, and 24 microgram/kg) at hourly intervals, from the induction of acute pancreatitis up to the 24th hour. A saline-treated group served as the control. The mortality rate was recorded, and pancreatic histology was evaluated by a scoring system. Serum amylase activity and pancreatic amylase, trypsin, protein, and desoxyribonucleic acid (DNA) contents were determined at 24 h. Administration of PGE1 influenced the severity of acute pancreatitis biphasically. Serum amylase was reduced significantly (p < 0.01) at a dose of 12 microgram/kg/h, but less at 24 microgram/kg/h. Pancreatic weights did not differ in the groups. Pancreatic amylase, trypsin, and protein contents showed significant elevations (p < 0.01), yet the mortality rate was reduced using 6 and 12 microgram/kg/h doses of PGE1 compared to controls, but not at higher and lower doses. The DNA content was significantly higher at the 6 microgram/kg/h dose, compared to the control. The extent of necrosis and the severity of hemorrhage were reduced significantly (p < 0.05) at doses of 6 and 12 microgram/kg/h of PGE1, but less at 24 microgram/kg/h. Leukocyte infiltration was not affected. In conclusion, optimal doses of PGE1 can ameliorate, but higher doses increase, the severity of acute pancreatitis in this experimental model.

Acute Disease↗

PubMed1995

Frequency source analysis in patients with brain lesions.

In a previous study (Harmony et al. 1993) we observed that the volume of lesions was correlated only with delta power, while the volume and density of edema showed a significant correlation with theta and alpha power, suggesting two independent origins of activity in the delta and theta bands in patients with space-occupying lesions. Our goal in this paper is to show, through a different technique, in a narrow band spectral analysis, that brain lesions are characterized by activity in the delta domain and that edema is better correlated with activity within the theta range. Frequency source analysis based on the Maximum Likelihood (ML) test for rejection of isotropicity was applied to the EEG at rest of 36 patients with space-occupying intracranial lesions. The ML test was rejected at frequencies below 1 Hz and in the low range of the delta rhythm in 31 patients. The origin of the equivalent dipoles at these frequencies was within the volume of the lesion in 27 patients. In 15 patients out of 19 with vasogenic edema the ML test was rejected at frequencies in the theta range. The equivalent dipoles at these frequencies were all within the volume of the edema.

Astrocytoma↗

PubMed1995

EEG activation patterns during the performance of tasks involving different components of mental calculation.

In this study we demonstrate the existence of different patterns of EEG activation during the performance of 4 different tasks involving different components of mental calculation in normal subjects. The EEG was recorded in all monopolar leads of the 10/20 system using linked ear lobes as reference. Absolute and relative power were calculated in the delta (1.5-3.5 Hz), theta (3.5-7.5 Hz), alpha (7.5-12.5 Hz) and beta (12.5-19 Hz) bands. The tasks were presented randomly and the EEG segments preceding presentation of the stimulus were considered as the rest corresponding to the task requested by the stimulus. Tasks were of 4 different types, involving number comprehension, recognition of mathematical symbols, the calculation process and the spatial component. ANOVAs between the rest periods showed no differences in any band. Neither did ANOVAs between tasks. However, other variables (task minus rest), which were calculated as the differences in power between task and rest respectively, showed significant differences between tasks in the delta and beta bands in the frontal lobes. In addition, new variables were calculated as the difference between tasks, since many factors were common across several tasks. These variables correspond to the EEG change due to a specific component of mental calculation. Significant differences were obtained in delta and theta bands in right posterior areas and in the beta band in frontal areas. We concluded that the EEG differences observed during different components of mental calculation suggest the participation of different networks.

Adult↗

PubMed1995

Comparison of Z and multivariate statistical brain electromagnetic maps for the localization of brain lesions.

Conventional Z maps provide probability statements about the deviation of observed values from the norm. Galán et al. (1994) introduced Simultaneous Significance Probability Scales to detect abnormalities over the whole map, making use of the information provided by the topographic structure of dependencies. They also described multivariate brain electromagnetic (MBE) maps for compact presentation of complex spatio-temporal information. In this paper, using the distance-based localization receiver operating characteristic curves (DL-ROC curves), we compare the localization provided by computed tomography with that provided by Z and MBE maps in 61 patients with brain lesions. Maps were calculated for absolute power and relative power in delta, theta, alpha and beta bands for voltage and current source densities (CSD). In each patient, all maps were compared and the map with the highest value of the area of the DL-ROC curve was considered to be the "best map." Z maps of CSD were the "best maps" in 24 patients. In the voltage montage, we observed that multivariate maps add some information not contained in the Z maps. However, for CSD, Z maps were more accurate than multivariate maps. A very consistent finding was the observation that lesions were better detected by maps analyzing the delta band, while edema was better represented by maps in the theta range.

Brain Damage, Chronic↗

PubMed1995

Longitudinal quantitative EEG study of children with different performances on a reading-writing test.

In a previous paper, using the same test for the evaluation of reading-writing abilities, Harmony et al. (1990b) reported that children with severe difficulties had more delta in fronto-temporal regions, and this was interpreted as a sign of underlying cerebral dysfunction. Children with severe and minor difficulties in the test had more diffuse theta absolute and relative powers and less alpha relative power. As theta decreases with age, while alpha increases, these results suggested that children with minor and severe difficulties in reading had a maturational lag with respect to those with normal performance. We conducted this study in order to test this hypothesis. Two different EEG records were obtained with an interval of 2.58-3.15 years in 49 children classified in 3 groups according to their performance in a reading-writing test. Group 1: adequate performance for age and degree (control group); group 2: below level performance with minor difficulties; and group 3: below level performance, with severe difficulties. The mean age of the groups in the first study was 9 years. Absolute (AP) and relative powers (RP) in the delta, theta, alpha and beta bands were computed for each session. In general, groups 3 and 2 showed greater changes than group 1 from session to session. ANOVAs performed by session clearly demonstrate many significant differences between groups in the first study, while few significant differences in parieto-occipital regions in theta RP were observed in the second session. These results point toward a maturational spurt of children from groups 2 and 3.

Brain↗