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Biomedical subjects

A Grabowska

Publications and source records attributed to A Grabowska.

At least 19 recordsLinked to original sources
PubMed1992

The effect of unilateral brain lesions on perception of visual illusions.

The study tested the effect of the left and right hemisphere lesions on the susceptibility to visual illusions. Twenty-five patients with left hemisphere damage, 22 patients with right hemisphere damage and 23 control subjects inspected series of figures producing four different illusions: Ponzo, Ehrenstein-Orbison, Poggendorff and Zoellner. Series of stimuli configurations were constructed so that different degrees of distortion opposite to the illusory effect were introduced in each pattern. The amount of distortion was increased in steps so that at a certain point of the series the patterns produced percepts opposite to the illusory ones. That point indicated the strength of the illusion. Stimuli of a given series were presented to each subject 5 times in random order and subject's judgements of illusions were collected. The illusion strength was established using the Spearman distribution method for determining psychophysical thresholds. The results showed that the left and right hemisphere lesions either did not affect the subject's susceptibility to illusions (in Ponzo and Poggendorff) or their effects were similar, i.e. they reduced the strength of the perceived illusions (in Ehrenstein-Orbison and Zoellner). Our data contradict the hypothesis of hemisphere differences in the perception of visual illusions and support the view that those phenomena are multiple-caused.

Attention↗
PubMed1992

Asymmetry in visual evoked potentials to gratings registered in the two hemispheres of the human brain.

The study aimed at testing, by a visual evoked potential method, the hypothesis of the hemispheric specialization in processing of high and low-spatial frequencies. Twenty four right-handed subjects (12 males and 12 females) were presented with square-wave vertical gratings of various spatial frequencies (0.67, 0.86, 1.20, 2.00, 2.40, 3.00, 3.30, 6.00 and 7.50 c/deg). Gratings were presented in nine separate blocks each containing 64 exposures. Time of exposure was 30 ms and the interstimulus interval varied from 2 to 3.5 s. VEPs were recorded with electrodes located at O1 and O2 and referred to Cz according to the 10/20 system. Amplitudes and latencies of two VEPs components (N130-150 and P200-240) were analyzed. The results showed larger amplitudes of VEPs registered in the right hemisphere of both males and females. This difference, however, was apparent in the earlier component of VEPs in females and in the later component in males. The observed hemispheric asymmetry did not depend on the spatial frequency of grating. Females demonstrated longer latencies than males for both N and P components. Our data suggest that the right hemisphere predominates in processing grating stimuli, but the dynamics of this process differ in the two sexes. The results do not support Sergent's hypothesis which postulate the right hemisphere specialization for low spatial frequencies and the left hemisphere specialization for high spatial frequencies.

Adult↗
PubMed1992

Hemispheric asymmetry in event related potentials associated with positive and negative emotions.

Event-related potentials from symmetrical points of the left and right frontal and occipital cortex were recorded while subjects experienced positive and negative emotions. The emotions were elicited by either missing or hitting a target with a photoelectric gun. Twenty three right-handers (10 males and 13 females) were tested. Each subject took part in two sessions. In the first session the subjects were informed about their performance (hit or miss) after each shot. In the second, control session, no feedback was given. The amplitudes of P180 potential registered from the occipital cortex were higher in the right than in the left cerebral hemisphere, irrespectively of subjects' performance (i.e. a miss or a hit). No such tendency was observed in potentials registered from the frontal cortex. These regularities emerged only in the feedback situation, i.e. when subjects were informed about their performance, although higher ERPs were registered for hits than for misses. The results support the hypothesis that the posterior region of the right hemisphere is more engaged than the left one in experiencing emotions, irrespectively of their sign.

Adolescent↗
PubMed1992

Instability of hemispheric asymmetry in dyslexic children.

The study tested the hypothesis of abnormal brain asymmetry in dyslexic children. Two dyslexic groups classified as "phonetic disorder" and "language disorder" and a control group participated in two experiments. In both experiments was employed a dichotic listening procedure consisting in recalling pairs of words presented simultaneously to two ears. In Experiment I the children were to recognize four words presented at a level of loudness typical for natural speech. In Experiment II only two words were used in each trial but they were presented at a low intensity level. The recognition scores for stimuli presented to the left and right ears were compared. In Experiment I all groups of children showed a typical right ear/left hemisphere superiority, i.e. their recognition scores were higher for the right than for the left ear. Dyslexics, however, performed significantly less well. In Experiment II the control children and those from "phonetic disorder" group again performed better when words were presented to their right ears. Unlike those two groups, the children from "language disorder group" showed the right hemisphere superiority, i.e. they performed better in the left ear presentation condition. The results do not support the hypothesis that dyslexic children have abnormal lateralization of verbal functions. They suggest that the pattern of hemispheric asymmetry in dyslexics is less stable and depends both on the kind of dyslexia and on task variation.

Brain↗
PubMed1990

Human trophoblast cells in culture express an unusual major histocompatibility complex class I-like antigen.

We present evidence that the trophoblast cells obtained from first trimester placentae by a culture method developed in our laboratory express a class I-like HLA antigen that is only sparsely distributed on the cell surface, lacks classical polymorphic determinants, and consists of heavy chains of lower molecular weight than those of classical HLA in association with beta 2-microglobulin (beta 2M). The latter two features are in general agreement with a previous report describing the nature of the HLA molecule on trophoblast disaggregated from term amniochorion. These cultured trophoblast cells could be useful for molecular studies of the unusual class I antigen, as well as for other in vitro experiments designed to mimic the in vivo local trophoblast-uterine interactions.

Antibodies, Monoclonal↗
PubMed1989

Impaired grating discrimination following right hemisphere damage.

We investigated the effect of unilateral brain lesions on visual discrimination of low-, middle- and high-frequency gratings. The performance of patients with right hemisphere lesions was significantly impaired compared with that of both controls and patients with left hemisphere lesions. This impairment was largely limited to patients with right posterior hemispheric lesions and was present with all spatial frequencies. These findings run counter to the hypothesis that high and low spatial frequencies are preferentially processed by different hemispheres.

Adult↗
PubMed1988

Left hemisphere superiority for visuospatial functions in left-handers.

Male and female left- and right-handers have been tested with a divided visual field technique on a visuospatial (discrimination of angle width) and on a verbal task (vowel-consonant discrimination) using either a choice or a Go-No-go manual reaction time paradigm. Right-handers showed the expected pattern of hemispheric asymmetries with an advantage of the right hemisphere in the visuospatial task and an advantage of the left hemisphere in the verbal task. Such effects were statistically reliable only in male subjects. Left-handers, on the contrary, showed a different pattern of asymmetries. In the visuospatial task there was an overall superiority of the left hemisphere, while no hemispheric asymmetry was found in the verbal task.

Adult↗
PubMed1988

[Incidence of simple goiter among the population of the Gołdap community].

The possibility of the occurrence of goiter endemia++ among the inhabitants of Gołdap community in the Suwałki voivodeship has been investigated. The investigations embraced 2488 persons, i.e. 21% of the population of the studied community. The occurrence of goiter was revealed in 38% of the investigated persons, and this observation lead to the conclusion that goiter is endemic among the population of the Gołdap community. Such features as high incidence of thyroid enlargement of low degree (OB and I), higher incidence of goiter in women than in men, absence of cases with hypothyroidism, and low incidence of nodular goiter, characterize the observed endemia++ as mild.

Adult↗
PubMed1979

Interactions between two spatially separated letters presented in succession.

The interactions between two letters presented in succession to neighboring regions of retina were investigated. The interstimulus intervals were: 0, 20, 60, 250 ms, 2.5 s. In control trials single letters were presented in two positions corresponding to the positions of letters in pairs. The recognition of a letter presented as the first element of pairs with either simultaneous presentation or with 250 ms delay of the second element was significantly better than the recognition of single letters. On the contrary, the interstimulus interval 20 and 60 ms yielded an increase of errors made in the recognition of the first letter. The results are interpreted in terms of inhibitory interactions between transient and sustained channels, and in terms of hypothesized excitatory connections between the cortical cells responding to visual elements forming more complex patterns.

Female↗
PubMed1979

Search for structures involved in integration of letters in pairs.

Two experiments aimed at finding, at what stage of perceptual processing the positive interactions between letters, observed in some previous studies, are established. Single letters and pairs of letters were exposed. The task of the subjects was to recognize letters. In Experiment I bright letters on a black background were used instead of black letters on bright background used in previous experiments. Such change of brightness within the stimuli did not influence the character of interactions between letters. This suggests that the positive interactions are connected with higher level of visual system. In Experiment II patients with damage of various areas of the brain cortex were tested. The facilitation between two letters did not occur in patients with prestriate lesions, although it can be observed in patients with different localization of lesions. This suggests that prestriate cortex is involved in positive interactions between letters.

Cerebral Cortex↗
PubMed1975

Interaction between two letters in visual perception.

Letters were exposed by tachistoscope for 17 ms to adult subjects. In Experiment I, single letters were exposed. The proportion of errors differed strongly for particular letters. In Experiment II pairs of letters were exposed. The first letter of a pair was recognized more easily than when exposed alone in Experiment I. In Experiment III pairs of letters were exposed but the subject's task was to recognize only one letter of the pair. Both, first and second letters of the pair were then recognized better than in Experiment I. The results were interpreted in terms of facilitatory and inhibitory effects occurring on different levels of the visual system.

Adult↗
PubMedDate not supplied

Isolation of human extravillous trophoblast cells by attachment to laminin-coated magnetic beads.

An isolation method has been developed based on laminin-coated magnetic beads which yields human trophoblast with a high degree of purity. Immunostaining with a panel of monoclonal antibodies indicates that these trophoblast cells are mainly of the extravillous variety. The mechanism for selection may be due to the expression of surface laminin receptors by these cells. This procedure, therefore, can provide appropriate cellular targets for in vitro assays against potential uterine effectors in studies on the local trophoblast-decidual interaction.

Cell Separation↗
PubMedDate not supplied

Interferon-gamma enhances mRNA and surface expression of class I antigen on human extravillous trophoblast.

Human trophoblast cells with immunocytochemical characteristics of the extravillous population have been isolated from 1st trimester placentae. Treatment of these cells with IFN-gamma increases the expression of Class I antigens at both the cell surface and mRNA level. A similar increase in Class I antigens is also found in JEG-3 choriocarcinoma cells after treatment with IFN-gamma. The possibility that aberrant production of IFN-gamma may upset the fetal-maternal equilibrium in vivo is discussed.

Antigens, Surface↗