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E Margalit

Publications and source records attributed to E Margalit.

9 recordsLinked to original sources
PubMed2003

Visual and electrical evoked response recorded from subdural electrodes implanted above the visual cortex in normal dogs under two methods of anesthesia.

Sensitive methods are required to record electrical evoked potentials over the visual cortex to evaluate the efficacy and safety of a retinal prosthesis before it can be implanted on the retinal surface of patients afflicted by outer retinal diseases. This study was designed to examine subdural electrodes as a mean to evaluate cortical evoked potentials in response to light and electrical stimulation of the retina in three dogs under two methods of anesthesia-halothane and propofol. Results showed that subdural electrodes could be stabilized over the visual cortex for several (3-5) months, and that they were 6.95 times more sensitive than subdermal electrodes in recording cortical visual evoked potentials (VEPs) and 4.31 times more sensitive in recording cortical electrical evoked potentials under both methods of anesthesia. The waveforms' shape changed for each electrode in the subdural array during 6/6 (100%) and 20/38 (52%) multi-channel recording sessions under halothane and propofol, respectively. This change could point to a cortical retinotopic organization versus hierarchical organization of different cortical areas for a given retinal stimulus. In summary, subdural electrodes show promising results for recording visual and electrical evoked responses (EERs) and thus for evaluation of the retinal prosthesis.

Anesthesia↗
PubMed2000

Bioadhesives for intraocular use.

BACKGROUND/PURPOSE: A safe, effective adhesive could be useful in the management of retinal holes or tears and selected complicated retinal detachments, as well as for attaching a small electronic device (retinal prosthesis) to the retina. In this study, we examined nine commercially available compounds for their suitability as intraocular adhesives. METHODS: The following materials were studied: commercial fibrin sealant, autologous fibrin, Cell-Tak, three photocurable glues, and three different polyethylene glycol hydrogels. An electronic strain gauge measured the adherence forces between different glues and the retina. The stability of hydrogels at body temperature and the impermeability of the hydrogel adhesive to dextran blue were examined. Long-term biocompatibility testing of the most promising glues in terms of adhesive force, consistency, and short-term safety (hydrogels) were done in rabbits. Funduscopy, electroretinogram, and histology of the retina were performed. RESULTS: Hydrogels had 2 to 39 times more adhesive force (measured in mN) than the other glues tested. They liquefied at body temperature after 3 days to a few months. Hydrogels were impermeable to dextran blue. One type of hydrogel proved to be nontoxic to the retina. CONCLUSIONS: Hydrogels proved to be superior for intraocular use in terms of consistency, adhesiveness, stability, impermeability, and safety.

Adhesiveness↗
PubMed1999

Sensory-motor transformation and motor planning in the primate frontal cortex.

To examine the role of the frontal cortex in sensory-motor processing, we trained a Rhesus monkey to perform a behavioral task with alternations between localization (LOC) and non-localization (NL) paradigms. In the LOC block, the monkey had to remember the modality and location of two sequential cues. Two different GO signals instructed the monkey to touch the memorized location of either auditory or visual spatial cues (GO-AUD or GO-VIS, respectively). In the NL paradigm the monkey received the same stimuli, but was instructed to touch a fixed target, disregarding the location and modality of the spatial and GO signals. Reaction time was significantly longer after GO-AUD signals in the LOC mode compared to the reaction time following GO-VIS signals, or in the NL mode. We examined 961 neurons in the frontal cortex and 427 parietal neurons. A group of frontal task-related neurons (72/430; 16.7%) showed evoked activity both after the visual and the GO-AUD stimuli in the LOC mode. The units did not respond to the GO-VIS signal that instructed the monkey to move to the same location, or to the identical stimuli in the NL mode. No such neurons were found in the sampled areas of the parietal cortex. Our findings suggest that the monkey initially planned a default response towards the location of the visual stimulus and immediately updated his motor plans when instructed to touch the memorized location of the auditory stimulus. We suggest that frontal activity may also be related to such modifications of sensory-motor associations.

Animals↗
PubMed1998

[Familial occurrence of Ebstein anomaly].

Ebstein anomaly is a rare congenital disease which affects location, structure and mobility of the tricuspid valve, and right atrium and ventricle. Although most cases are sporadic, familial occurrence has been reported. We report 2 brothers born with Ebstein anomaly. The parents were first degree cousins and there were 8 other children. 2 daughters were born with other congenital heart anomalies, 1 with ventricular septal defect and the other with severe pulmonary artery stenosis. We suggest that in some families, Ebstein anomaly is an autosomal dominant disease with different expression in the sexes.

Adolescent↗
PubMed1993

Spatiotemporal firing patterns in the frontal cortex of behaving monkeys.

1. Activity of up to 10 single units was recorded in parallel from frontal areas of behaving monkeys. 2. Spatiotemporal firing patterns were revealed by a method that detects all excessively repeating patterns regardless of their complexity or single-unit composition. 3. Excess of repeating patterns was found in 30-60% of the cases examined when timing jitter of 1-3 ms was allowed. 4. An independent test refuted the hypothesis that these patterns represented chance events. 5. In a given behavioral condition there were usually many different patterns, each repeating several times, and not one (or a few) pattern repeating many times. 6. In 13 out of 20 cases, when a single unit elevated its firing rate in association with an external event beyond 40/s, most of the spikes within that period were associated with excessively repeating spatiotemporal patterns. 7. Of 157 types of patterns whose excess was most marked, 107 were composed of spikes from one single unit, 45 of the patterns contained spikes from two single units, and only one was composed of spikes from three different single units. 8. These properties suggest that the patterns were generated by reverberations in a synfire mode within self-exciting cell assemblies.

Animals↗
PubMed1991

Neural interactions in the frontal cortex of a behaving monkey: signs of dependence on stimulus context and behavioral state.

In order to gain an understanding of the processes taking place within and between neuronal assemblies, we made simultaneous recordings of spike trains from groups of up to 11 neurons in the frontal cortex of a rhesus monkey, that was trained to perform a sensorimotor behavioral task. We report here on preliminary results from correlation analysis of these neuronal activities, with special emphasis on signs of behaviorally induced modifications of neural interaction, possibly due to rapid modulations of discharge synchronization among the neurons. Our findings suggest that different functional groups of neurons may co-exist within each small volume of cortex, and that neurons may be dynamically recruited into such a group to fulfil a specific function.

Animals↗