PubMed Health⌕ Search

Biomedical subjects

R B Katz

Publications and source records attributed to R B Katz.

17 recordsLinked to original sources
PubMed1992

Use of hair analysis for evaluating mercury intoxication of the human body: a review.

Relationships have been established between the concentrations of mercury in human scalp hair and environmental or dietary mercury exposures. For chronic exposures, the hair/blood ratio for mercury is in the range 200:1-300:1, and scalp hair mercury concentrations of greater than 5 ppm are indicative of mercury intoxication. These observations, coupled with the ease by which samples may be collected, transported and stored, support the use of hair analysis for evaluating mercury intoxication of the human body.

Environmental Exposure↗
PubMed1992

Automatic activation of word phonology from print in deep dyslexia.

The performance of deep dyslexics in oral reading and other tasks suggests that they are poor at activating the phonology of words and non-words from printed stimuli. As the tasks ordinarily used to test deep dyslexics require controlled processing, it is possible that the phonology of printed words can be better activated on an automatic basis. This study investigated this possibility by testing a deep dyslexic patient on a lexical decision task with pairs of stimuli presented simultaneously. In Experiment 1, which used content words as stimuli, the deep dyslexic, like normal subjects, showed faster reaction times on trials with rhyming, similarly spelled stimuli (e.g. bribe-tribe) than on control trials (consisting of non-rhyming, dissimilarly spelled words), but slower reaction times on trials with non-rhyming, similarly spelled stimuli (e.g. couch-touch). When the experiment was repeated using function words as stimuli, the patient no longer showed a phonological effect. Therefore, the phonological activation of printed content words by deep dyslexics may be better than would be expected on the basis of their oral reading performance.

Dyslexia↗
PubMed1991

Limited retention of information in the graphemic buffer.

This study examined a patient who mainly made letter deletion errors in spelling. It was hypothesized that his errors were due primarily to limited ability to retain information in the graphemic buffer, a structure that holds sequences of abstract letter identities for output. Consistent with this hypothesis, the patient's spelling accuracy declined on long words, but the number of letters he wrote per response was not related to word length. Moreover, by having him write words forward and backward, it was shown that his accuracy within a word depended on which part of the word he tried to output first. These results also ruled out alternative accounts of the patient's spelling deficit based on neglect or damage to lexical representations.

Anomia↗
PubMed1991

Distinguishing representation deficits and processing deficits in a case of acquired dysgraphia.

The same acquired disorder of spelling may be due to deficits affecting lexical representations of word spelling or deficits affecting the mechanisms that process those representations. This study sought to distinguish these possibilities in a dysgraphic patient. The integrity of the patient's lexical orthographic representations was assessed by having him decide whether or not pairs of words presented auditorily rhymed. Although the patient was impaired on a variety of spelling tasks and with all types of stimulus material, he showed a normal effect of spelling on the rhyme task. Like normal subjects, he was faster at deciding that words rhymed when they were spelled similarly (e.g. tool-cool) than when they were spelled dissimilarly (e.g. rule-cool) and slower at deciding that words did not rhyme when they were spelled similarly (e.g. toad-broad) than when they were spelled dissimilarly (e.g. code-broad). Therefore, as the patient's lexical representations of word spelling seemed to be generally intact, his spelling problems were probably due to difficulty in processing those representations.

Agraphia↗
PubMed1990

Deep dysphasia: analysis of a rare form of repetition disorder.

"Deep dysphasia" is the parallel in repetition to the reading impairment deep dyslexia. Our patient, S.M., showed part of speech, word/nonword, and concreteness effects in repetition, and he made semantic errors, but his oral reading was relatively spared. Further testing indicated that S.M. did not have difficulty perceiving spoken stimuli or deciding their lexical status, but he was deficient at semantically processing spoken words. Moreover, his phonemic memory was severely impaired. We argue that the routes for repetition (lexical and nonlexical) that function without semantic mediation were defective and that deficits in phonemic memory further diminished their effectiveness, since initial phonological encoding of spoken words was not available to guide the output stages of phonological processing. In addition, the semantically mediated route for repetition was unreliable because semantic processing was faulty and S.M. could not accurately label concepts.

Aged↗
PubMed1990

Cross-modality word matching in letter-by-letter readers.

Letter-by-letter readers can match spoken words to printed words they cannot read. Good word-matching ability may be attributable to a priming effect. However, since letter-by-letter readers have intact spelling ability, an alternative hypothesis is that word matching depends on a strategy of scanning printed words for recognizable letters known to be in the target items. In the present study, experimental manipulations that taxed the ability of the two subjects to process key letters (those that distinguished target words from foils) or scan for them caused a decline in word-matching performance. Thus, letter-by-letter readers may rely on sequential letter processing to accomplish cross-modality word matching.

Aged↗
PubMed1989

Recognizing orally spelled words: an analysis of procedures shared with reading and spelling.

Some investigators have suggested that recognizing orally spelled words is dependent on the same procedures ordinarily used in spelling, whereas others have viewed it either as dependent on reading procedures or as an independent ability. In the present study, a single subject with dyslexia and dysgraphia was examined on parallel tests of recognizing orally spelled words, reading, and spelling (writing), and a comparison was made of his performance on the three tasks. On both words and nonwords, the patient's errors in recognizing orally spelled words and in reading were alike, whereas his spelling errors were often different. The distinction between recognizing orally spelled words and spelling was further shown by his inability to recognize a set of orally spelled words that he could write correctly to dictation or on the basis of word meaning. These findings suggest that the procedures normally used for reading can accept sequences of letter identities as input when orally spelled words must be recognized.

Agraphia↗
PubMed1989

Positional dyslexia.

Position-specific errors in word reading are usually associated with neglect or visual extinction on the same side as the reading problem. In this study, two patients with left-hemisphere lesions showed visual extinction on the right but reading difficulty on the left side of words and pseudowords. Further study of one patient revealed that he also had problems reading the beginning of words presented tachistoscopically or in vertical orientation. In addition, the positional difficulty was apparent when he named the letters in words. The pattern of results indicates that the positional dyslexia in these patients was not likely attributable to general deficits in visual perception or attention but may have reflected a disorder at a later stage of letter processing.

Attention↗
PubMed1989

Elevated blood levels of carcinogens in passive smokers.

The hypothesis that involuntary exposure to tobacco smoke--passive smoking--results in greater risk of cancer was assessed by measuring the levels of two known carcinogens in the blood of 57 nonsmokers with varying degrees of involuntary exposure, including six heavily exposed bartenders. The concentrations of hemoglobin adducts of 4-aminobiphenyl, a bladder carcinogen, were significantly higher in subjects with confirmed involuntary exposure (plasma cotinine concentrations between 2 and 23 ng/ml) compared with subjects with undetectable levels of cotinine. Similarly, adducts of 3-aminobiphenyl were significantly elevated in subjects with confirmed exposure. The odds of 3-aminobiphenyl adduct levels exceeding 2 pg/g of hemoglobin were 6:7 among the confirmed exposed, compared with the odds of 2:42 among subjects with undetectable cotinine (odds ratio = 18; 95 percent confidence interval = 3.3, 94). The validity of the assay was demonstrated by showing striking declines in adduct levels among quitting smokers.

Adult↗
PubMed1987

Accurate reading by nonlexical means: a case study.

Accurate reading of irregular words is generally assumed to require intact lexical reading mechanisms. A nonlexical mechanism is usually deemed insufficient for this type of stimulus processing. The maximum level of accuracy attainable by nonlexical means, however, has not been adequately evaluated. We now describe a patient with acquired dyslexia due to impaired lexical reading mechanisms who retained the ability to read irregular words. The patient's poor performance on tasks requiring lexical decision and access to word meaning provided evidence that his lexical mechanisms were impaired. Nevertheless, errors on irregular words became apparent only with special tests that circumvented the patient's ability to use his intact speaking vocabulary to ensure that reading responses were words. The results demonstrate that relatively accurate reading of irregular words is possible despite damage to lexical mechanisms and that this can be achieved by filtering potential responses through the speaking vocabulary.

Dyslexia, Acquired↗
PubMed1985

Repetitive naming and the detection of word retrieval deficits in the beginning reader.

The claim has been advanced that children with severe reading disability are generally deficient in word retrieval compared with normal readers. Support for the claim is based largely on studies of rapid naming of repetitively presented pictured objects or other nameable stimuli, a task which is apparently more sensitive to retrieval problems than the confrontation naming of items presented singly. The purpose of this study was to examine whether there is a general relationship between word retrieval speed and reading ability in beginning readers. Although such a relationship has not been detected with confrontation naming, repetitive naming may provide a more sensitive test. Accordingly, second-grade children were required to name as rapidly as possible repeated presentations of five pictured items drawn from a single category. Separate naming tests were made for objects, colors, animals, letters, and words. The results showed that there was no relationship between reading ability and naming times when the test items were selected from sets of objects, colors, or animals, whereas on letters and words, a significant relationship was found. The less-skilled readers were not, therefore, consistently slower in all repetitive naming situations. Instead their word retrieval deficits extended only to the orthographic materials.

Child↗
PubMed1979

The brow-lift 1978.

The direct brow-lift for correction of brow ptosis can be one of the most beneficial surgical procedures in cosmetic surgery. Careful preoperative evaluation and proper symmetrical marking of the correction are key elements for successful results. We discuss the surgical technique in detail.

Eyebrows↗
PubMed1975

Benign mesothelial tumor of bladder.

Two cases of benign mesothelial tumor of the bladder are presented, one causing urinary retention following surgery for stress incontinence and the other a softball-sized fibroma with a fifteen-year follow-up.

Female↗
PubMedDate not supplied

Hearing loss of a central type secondary to anoxic anoxia.

The effect of anoxic anoxia on the threshold sensitivity and amplitude of the responses from the auditory cortex, inferior colliculus and cochlea to acoustic stimuli in guinea pigs was studied. Decay of the amplitude of the responses from the auditory cortex and the inferior colliculus occurs faster and is more severe than that of the cochlea. Recovery of the amplitude of the responses is slower at the auditory cortex and the inferior colliculus than at the cochlea. Loss of auditory threshold sensitivity in anoxic anoxia is most prominent at the auditory cortex. The loss of sensitivity at the inferior colliculus is the next most severe. The loss of sensitivity at the cochlea is negligible. The relative vulnerability of the central auditory pathway to anoxic anoxia as compared to the end organ is demonstrated.

Animals↗
PubMedDate not supplied

A method for determining cortical auditory thresholds in guinea pigs.

A method for measuring evoked cortical potentials to acoustic stimuli through the intact dura mater of the guinea pig without computer averaging studied. After exposure of the dura overlying the auditory cortex on the left side, thresholds to acoustic stimuli presented to the right ear were determined with a double tipped silver electrode by visual detection on an oscilloscope. The thresholds obtained are compared with other methods of determining audibility levels in the guinea pig. With relatively simple instrumentation, this method provides rapid and accurate determination of the audibility curve.

Acoustic Stimulation↗