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Biomedical subjects

M Weisbrod

Publications and source records attributed to M Weisbrod.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Delirium syndrome as a side-effect of lithium in normal lithium levels].

Lithium is used with great success in the treatment of manic patients and for prophylaxis of bipolar disorders. There are only few reports about neuropsychiatric side effects at therapeutic serum levels. We report on a 38 year old woman with bipolar disorder who was treated with lithium for 20 years without side-effects. Subsequent to a manic episode, she became disoriented at night and showed marked memory deficits. The patient did not show any neurological or gastrointestinal signs of intoxication. Lithium serum-levels were in therapeutic range. The psychiatric symptoms disappeared when lithium was stopped. We interpret these symptoms as delirant syndrome with pseudo-dementia at therapeutic lithium serum levels. This side-effect must be taken into account even in patients on successful longtime lithium therapy.

Adult↗
PubMed2000

[Life-threatening echovirus 11 infection during first month of life].

Infection with Echovirus 11 is mostly asymptomatic, but it may cause a wide variety of clinical diseases, from gastroenteritis to serious diseases such as meningitis and myocarditis. In small infants, especially during the first days of life, echovirus infection may appear as a sepsis-like illness, and cause disseminated intravascular coagulopathy and shock. We present 2 infants with severe Echovirus 11 infections. A 3.5-month-old died within 24 hours of shock and probably myocarditis. The other, 6-days old, presented with meningitis, hepatitis and disseminated intravascular coagulopathy. It recovered after treatment with intravenous immunoglobulin. Echovirus 11 may cause life-threatening infections in small infants. Pediatricians should be alert to the special characteristics of this disease.

Disseminated Intravascular Coagulation↗
PubMed2000

Feeding tolerance of ready-to-use versus powdered formulas in neonates.

BACKGROUND: Following the introduction of ready-to-use formula in our neonatal department, we observed an increase in the number of neonates regurgitating after feeding. OBJECTIVE: To compare the feeding tolerance of neonates, in terms of regurgitations, to ready-to-use versus powdered formulas. METHODS: We compared the number of regurgitations in 727 healthy neonates after feeding ready-to-use formulas and powdered formulas of two different manufacturers. Six groups of neonates were formed, three for each manufacturer. Each of the two groups was fed with either ready-to-use formula or with reconstructed powdered formula (using a two-compartment patented feeding bottle called Twist 'N Feed) and one group received both preparations during 2 successive days. RESULTS: The groups that were fed only with ready-to-use formulas had significantly more regurgitations than those fed with powdered formulas. Within the group that received both types of formulas there were significantly more regurgitations following the ready-to-use than the powdered formula. CONCLUSIONS: Feeding tolerance, in terms of regurgitations, was significantly better in neonates fed reconstituted powdered formula as opposed to ready-to-use formulas. More studies are required to determine the exact mechanism for these differences.

Female↗
PubMed1999

Electrophysiological correlates of direct versus indirect semantic priming in normal volunteers.

The N400 component of event related potentials (ERP) was studied in 27 right-handed healthy subjects in a speeded lexical decision task. The semantic distance between primes (always words) and targets (50% words, 50% non-words) was systematically varied. Prime-target relations included directly related words (hen-egg), indirectly related words (lemon-sweet), and non-related words (sofa-wing). ERPs were recorded from 20 scalp electrodes positioned according to the international 10-20 system. The N400 reflected semantic distance with the most negative and latest N400 peak in the non-related condition, the least negative and earliest N400 peak in the direct condition and the peak in the indirect condition in-between. Hence, N400 priming effect in the indirect condition was obtained in the absence of strong sentential constraints and even though the mediating word was physically not present.

Adult↗
PubMed1999

Genetic influence on auditory information processing in schizophrenia: P300 in monozygotic twins.

BACKGROUND: It is widely accepted that schizophrenia is to some extent genetically determined. Abnormalities of the P300 component are one of the most robust biological findings in schizophrenia. They outlast clinical impairment and are present also in relatives of schizophrenic patients. In the present study on schizophrenic twins, the heritability of auditory P300 abnormalities and the influence of task difficulty on heritability was examined. METHODS: Twenty-two monozygotic twin pairs were included into this study (eight pairs discordant, five pairs concordant for schizophrenia or schizoaffective psychosis according to ICD-10 criteria, and nine control pairs). Two different versions of the auditory oddball paradigm were used to control for deficient stimulus perception. RESULTS: Compared to healthy controls, P300 amplitudes were significantly smaller in affected twins as well as in the non-affected co-twins of the discordant pairs. CONCLUSIONS: Our results suggest that P300 amplitude reduction is a genetically transmitted vulnerability marker for schizophrenia. Because the findings were independent of the difficulty of the task and could be demonstrated even when pitch disparity was adjusted to the subjects' ability to discriminate tones, the findings can not be related to the genetic influence on higher information processing.

Adult↗
PubMed1999

Tracking the time course of object categorization using event-related potentials.

Object categorization processes were investigated by measuring event-related potentials while subjects categorized objects at the superordinate (e.g. animal), basic (e.g. dog) and subordinate (e.g. beagle) levels of abstraction. An enhanced negative deflection (N1) was found at posterior recording sites for subordinate level categorizations compared with basic level categorizations and was interpreted as a marker of increased visual analysis. In contrast, superordinate level categorizations produced a larger frontal negativity relative to basic level categorizations and were interpreted as an indicator of increased semantic processing. These results suggest a neurophysiological basis for the separate cognitive processes responsible for subordinate and superordinate object categorizations.

Adult↗
PubMed1999

The relation between asymmetry and amplitude of the P300 field in schizophrenia.

OBJECTIVES: A general reduction of auditory P300 amplitude is one of the most consistently replicated observations in schizophrenic patients. However, a left hemisphere amplitude reduction is discussed controversely. METHODS: Encouraged by this controversy we analysed P300 data of 53 controls and 60 patients of the schizophrenia spectrum (ICD-10: F20, F23, F25). RESULTS: Our main result was the finding of the correlation between general amplitude and hemispheric asymmetry in the patient group: low general amplitudes were assigned to a left hemispheric amplitude reduction, high amplitudes to a right hemispheric reduction. Based on this result, we grouped all subjects according to their hemispheric asymmetry pattern. The control group and the group of schizoaffective patients (F25) with a left hemispheric amplitude reduction showed the inverse asymmetry pattern of P300 amplitude compared to subjects with a right hemispheric amplitude reduction. In contrast, the schizophrenic patients (F20) showed only a difference in P300 amplitudes measured at electrode sites of the left hemisphere. Additionally, we could show, that the amount of the general amplitude reduction in patients was different between the diagnostic groups. CONCLUSIONS: We conclude that a left hemispheric amplitude reduction is not a general feature of schizophrenia but it seems to be pathological when combined with a general amplitude reduction.

Acoustic Stimulation↗
PubMed1998

Right hemisphere activation during indirect semantic priming: evidence from event-related potentials.

Healthy subjects performed a lexical decision task in a semantic priming paradigm while event-related potentials (ERPs) were recorded from 64 channels. Semantic distance between prime and target was varied by including directly, indirectly, and nonrelated word pairs. At centro-parietal electrodes an N400 to nonrelated pairs was elicited bilaterally which was sensitive only to direct, but not to indirect semantic priming. These N400 priming effects were mirrored by the RT data. At inferior fronto-temporal sites directly related words showed ERP priming effects over both hemispheres. However, indirectly related words only elicited ERP priming effects over the right hemisphere. These results support the hypothesis that the right hemisphere semantic system is involved in processing of remote semantic information.

Adult↗
PubMed1998

The time course of brain activations during response inhibition: evidence from event-related potentials in a go/no go task.

The cortical organization of executive control was investigated using event-related potentials (ERPs). ERPs were collected while subjects performed a go/no go task that required response inhibition. First, around 260 ms after stimulus onset, an effect of response inhibition on ERPs was observed over inferior prefrontal areas. Generators in these regions were confirmed by source analysis. Later, between 300-600 ms after stimulus onset, a left lateralized fronto-central ERP effect was found which differed in topography from a non-specific effect of task difficulty. Source analysis indicated that generators in anterior cingulate and left premotor areas also contributed to this effect. Orchestrated activation of prefrontal areas and the anterior cingulate subserves executive function whereas relatively late activity of the left premotor cortex is involved in motor control.

Adult↗
PubMed1998

Functional magnetic resonance imaging of category-specific cortical activation: evidence for semantic maps.

Functional magnetic resonance imaging (fMRI) was used to examine the pattern of cortical activity during a picture naming task. Subjects (n=12) had to covertly name either animals or furniture items. Functional scanning was performed using a conventional 1.5-Tesla whole-body MRI system. Images obtained during naming the two categories were compared using a non-parametric test. The study revealed evidence for domain-specific lexical regions in left middle, right middle and inferior frontal areas, as well as in superior and middle temporal areas. The results corroborate neuropsychological data and demonstrate directly and non-invasively in human volunteers that semantic representations in frontal and temporal areas are, to some degree, localized and possibly implemented as multiple maps. A completely distributed storage of semantic information is rendered unlikely.

Adult↗
PubMed1998

Lateralised semantic and indirect semantic priming effects in people with schizophrenia.

BACKGROUND: In schizophrenia, disturbances in the development of physiological hemisphere asymmetry are assumed to play a pathogenetic role. The most striking difference between hemispheres is in language processing. The left hemisphere is superior in the use of syntactic or semantic information, whereas the right hemisphere uses contextual information more effectively. METHOD: Using psycholinguistic experimental techniques, semantic associations were examined in 38 control subjects, 24 non-thought-disordered and 16 thought-disordered people with schizophrenia, for both hemispheres separately. RESULTS: Direct semantic priming did not differ between the hemispheres in any of the groups. Only thought-disordered people showed significant indirect semantic priming in the left hemisphere. CONCLUSIONS: The results support: (a) a prominent role of the right hemisphere for remote associations; (b) enhanced spreading of semantic associations in thought-disordered subjects; and (c) disorganisation of the functional asymmetry of semantic processing in thought-disordered subjects.

Analysis of Variance↗
PubMed1998

Adult epiglottitis: the Toronto Hospital experience.

OBJECTIVE: This study was conducted to gain insight into the diagnosis, treatment, and outcome measures in adult patients presenting with acute epiglottitis. METHOD: A retrospective clinical study was conducted on fifty-seven consecutive adult patients presenting with acute epiglottitis over a 13-year period to The Toronto Hospital, University of Toronto. Demographic description of patient population, presenting symptoms and signs, investigations performed, treatment provided, and incidence of complications were described. RESULTS: Soft-tissue lateral neck x-rays were abnormal in 88.1% of patients tested but had a 12% false-negative rate. Indirect, direct, or flexible laryngoscopy were the most accurate investigations to establish diagnosis and were not associated with any complications. Four of 45 patients (8.9%) had positive blood cultures for Haemophilus influenzae, with the remainder demonstrating no growth, while 22% of patients (8/36) grew possible pathogenic organisms on throat culture. A rapid clinical course (< 12 hr), evidence of tachycardia, or positive pharyngeal or blood cultures were factors that selected for a group of patients requiring formal airway intervention. CONCLUSIONS: Adult epiglottitis is different from its paediatric counterpart in that organism identification is less common, the clinical course is more gradual, there is less seasonal variation, airway compromise is more uncommon, and conservative airway management can be contemplated in the selected patient. Adult epiglottitis can be managed safely with a selective approach to airway management with airway intervention for any patient with signs of critical airway compromise.

Acute Disease↗
PubMed1997

Left lateralized P300 amplitude deficit in schizophrenic patients depends on pitch disparity.

The general reduction of P300 amplitude in response to auditory oddball stimuli is one of the most consistently replicated biological observations in schizophrenic patients. Several groups have reported a P300 asymmetry in schizophrenic patients, others have not been able to replicate this finding. In order to clarify this issue, we examined the effect of stimulus discriminability on P300 amplitude distribution in schizophrenic patients and in age-matched normal control subjects, using two different auditory oddball paradigms. The detection of the target tone was either simple or difficult, due to manipulation of pitch disparity. The P300 amplitude was comparatively smaller in the schizophrenic patient group compared to the healthy controls and in the difficult task compared to the simple. The schizophrenic patients showed a specific P300 amplitude reduction over left temporal electrode sites when the simple paradigm was used. The difficult paradigm did not elicit asymmetrical P300 amplitudes in schizophrenic patients.

Adult↗
PubMed1997

[Event-related potentials in semantic speech processing by schizophrenic patients].

Event-related potentials (ERPs) can be used for high-resolution mental chronometry. For about 15 years, this method has been applied to the study of linguistic phenomena. Semantic incongruency produces a negative component at about 400 ms after stimulus onset, the N400. We measured the N400 component in 20 schizophrenic patients and 20 normal control subjects performing a lexical decision task in which semantic distance between prime and target was varied. The results provide evidence of dysfunctional semantic information processing in schizophrenic patients, and reaction time data from previous studies can be interpreted within an electrophysiological framework. The N400 amplitude and latency data support recent spreading activation models of schizophrenic language dysfunction.

Adult↗
PubMed1996

Dopaminergic modulation of semantic network activation.

In order to examine the effect of dopamine on semantic processing, we performed a double-blind, placebo-controlled study. Healthy volunteers (n = 31) were tested in a lexical decision paradigm after ingestion of either L-dopa 100 mg with benserazide 25 mg or placebo. While direct semantic priming was influenced only marginally by L-dopa, the indirect priming effects was reduced significantly. These data support the hypothesis that dopamine increases the signal-to-noise ratio in semantic networks by reducing the spread of semantic processing, thereby leading to a focussing of activation.

Adult↗
PubMed1995

[Brain ultrasonography in diagnosis of intrauterine infections and of neonatal chromosomal disorders].

Ultrasonography of the brain is a primary, frequently used technique for the diagnosis of brain lesions in the neonate. Echogenic blood vessels in the thalamus and basal nuclei are an unusual finding in an ultrasonographic homogeneous area. We describe 2 neonates with echogenic blood vessels in this area who are, to our knowledge, the first such cases described in Israel: 1 with trisomy 13 and the other with a congenital cytomegalovirus infection. We focus pediatric attention on this simple, readily available method for diagnosing intrauterine infections and chromosomal aberrations in the neonate.

Abnormalities, Multiple↗
PubMed1995

A neural network model of phantom limbs.

This paper presents a detailed clinical description of phantom limbs and a neuronal network model that provides a comprehensive and parsimonious explanation of otherwise inexplicable or at least unrelated phenomena. Simulations of self-organizing feature maps (Kohonen networks) that had been trained to recognize input patterns were deprived of parts of their input in order to simulate partial deafferentation. This leads to reorganization processes that are shown to be driven by input noise. In patients with an amputated limb, this noise is generated by dorsal root ganglion sensory neurons which are known to fire irregularly upon laceration. According to this model, the long-standing debate concerning non-cortical vs. cortical contributions to the generation of the phenomenon of phantom limbs can be resolved in that it is the peripherally generated noise that causes cortical reorganization. The model can be tested and may have therapeutic implications.

Cerebral Cortex↗