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Biomedical subjects

D Caplan

Publications and source records attributed to D Caplan.

At least 19 recordsLinked to original sources
PubMed2002

Anatomy of stroke, Part I: an MRI-based topographic and volumetric System of analysis.

BACKGROUND AND PURPOSE: The clinical diagnosis and treatment of stroke, as well as investigations into the underlying pathophysiology of the disease, hinge on inferences from the anatomy of the stroke lesion. We describe an MRI-based system of topographic and volumetric analysis that considers distribution of infarct with respect to neuroanatomic structures, superficial and deep perfusion compartments, and gray and white matter tissue types. METHODS: MRI-based 3-dimensional topographic and volumetric analysis of presumed MCA embolic stroke was performed months after the acute event in 21 subjects ranging in age from 34 to 75 years. RESULTS: The topography of infarction was greatly variable, with virtually all regions of the MCA territory involved in at least 1 stroke in the series. In 14, there was involvement of the M1 as well as the M2 through M4 territories; in 6, there was involvement of only the M2 through M4 territories; and in 2, there was involvement of only the M1 territory. The volumes varied from 3.1 to 256 cm3, corresponding approximately to a range of 1% to 90% of the total MCA territory. CONCLUSIONS: The system of topographic and volumetric analysis is generally applicable to all strokes in the forebrain where the infarct is visualized in MRI, independent of vascular territory, clinical correlates, and interval between stroke and MRI. The results emphasize the variety of topographic patterns and lesion volumes of strokes. Intended long-range applications include correlation of outcome of stroke with predictions from acute-phase diffusion- and perfusion-weighted imaging and investigations of the potential benefit of therapeutic agents.

Adult↗
PubMed2002

Anatomy of stroke, Part II: volumetric characteristics with implications for the local architecture of the cerebral perfusion system.

BACKGROUND AND PURPOSE: The margin of a stroke is assumed to approximate a trace of the isobar of the perfusion threshold for infarction at the time that infarction occurred. Working from this hypothesis, we have analyzed stroke topography and volume in MR images obtained at a time remote from the stroke event. We have derived parameters from these images that may give information on local perfusion competence and microvascular architecture because they influenced the contour of stroke at the time infarction occurred. METHODS: MR images were obtained months after presumed embolic middle cerebral artery stroke in 21 subjects. Volumetric analyses of image data were undertaken with respect to the tissue shape of stroke and scaling ratios of anatomic partitions involved in stroke. RESULTS: For stroke confined to a single volume, the 3-dimensional form conforms to a parabola in which the height-to-width ratios are variable. The ratio for cortex is greater than that for underlying white matter. Scaling ratios indicate a close correlation between volume of cortex and radiata destroyed and total volume of stroke, but the relative proportions vary as a function of location within the M4 territory. CONCLUSIONS: Scaling ratios for cortex and radiata to stroke volume are consistent with vascular studies that depict a modular microvascular perfusion architecture for the cortex and underlying white matter. The stroke descriptors are inferred to be related to the competence of collateral perfusion at the time that stroke occurred. This inference may be tested by serial volumetric analysis of the perfusion-diffusion examination mismatch immediately and over the longer-term evolution of stroke.

Adult↗
PubMed2001

Memory and encoding of spoken discourse following right hemisphere damage: evidence from the Auditory Moving Window (AMW) technique.

We investigated the hypotheses that impaired discourse processing following right hemisphere damage is mediated by task difficulty and is associated with deficits in discourse encoding. Spoken discourse passages differing in contextual predictability were presented to right hemisphere-damaged (RHD) patients and to non-brain-damaged (NBD) controls for subsequent recall using the Auditory Moving Window paradigm. To manipulate processing difficulty, speech segments were of normal or accelerated speech rates. The recall results showed that RHD adults recalled less than NBD controls overall and failed to recall major idea units better than minor idea units for high predictability passages presented at accelerated speech rates. Both RHD patients and NBD controls failed to recall major idea units better than minor idea units for low predictability passages, regardless of speech rate. The encoding results showed that RHD adults were both slower overall and differentially slower than NBD controls when listening to accelerated passage segments. Taken together, the encoding and recall results are consistent with the view that extracting passage gist under difficult listening conditions is especially vulnerable for patients with right hemisphere strokes.

Adult↗
PubMed2001

Functional neuroimaging studies of syntactic processing.

This paper reviews studies of the functional neuroanatomy of syntactic processing using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI), focusing on interpretability of studies and the model of functional neuroanatomy that emerges from existing work. It is argued that existing studies suggest a specialization for one aspect of syntactic processing in the left inferior frontal cortex in proficient language users, with variability in this localization across the entire population.

Brain↗
PubMed2001

Effect of topical alendronate on root resorption of dried replanted dog teeth.

Alendronate (ALN) is a third generation bisphosphonate with demonstrated osteoclast inhibitory activity that may slow down the resorptive process after severe traumatic injuries. Eighty-two premolar roots of five mongrel dogs were endodontically treated and restored, extracted and treated as follows: 70 roots were bench dried for either 40 or 60 min. Thirty-eight of these roots were then soaked for 5 min in a 1 mM solution of ALN in Hanks' Balanced Salt Solution (HBSS) and replanted. Thirty-two roots were soaked for 5 min in HBSS and replanted. In the remaining 12 roots which were not exposed to the bench drying procedure, a 0.5 mM deep lingual mid-root cemental defect was made. Six of these roots were soaked in a 1 mM solution of ALN in HBSS for 5 min and replanted. The other six roots were soaked for 5 min in HBSS and replanted. Historical negative and positive controls were used from similarly treated teeth in our previous studies. After 4 months the dogs were killed and the roots prepared for histological evaluation. Five-microm-thick cross-sections of the root and surrounding tissue taken every 70 microm were evaluated for healing according to the criteria of Andreasen. In the 12 roots with cemental defects, healing with cementum of the damaged root surface was evaluated. In addition, residual root mass was also measured to determine the extent of root structure loss for each soaking method. Cemental healing took place in all 12 artificially damaged roots, indicating that these soaking media did not inhibit cementogenesis. The alendronate-soaked roots had statistically significantly more healing than the roots soaked in HBSS without alendronate. This improvement in healing was seen in all dogs except one and in all teeth except the first premolar. Soaking in alendronate also resulted in significantly less loss in root mass due to resorption compared to those teeth soaked in HBSS without alendronate.

Administration, Topical↗
PubMed2001

Age, working memory, and on-line syntactic processing in sentence comprehension.

One hundred twenty-seven individuals who ranged in age from 18 to 90 years were tested on a reading span test and on measures of on-line and off-line sentence processing efficiency. Older participants had reduced working-memory spans compared with younger participants. The on-line measures were sensitive to local increases in processing load, and the off-line measures were sensitive to the syntactic complexity of the sentences. Older and younger participants showed similar effects of syntactic complexity on the on-line measures. There was some evidence that older participants were more affected than younger participants by syntactic complexity on the off-line measures. The results support the hypothesis that on-line processes involved in recognizing linguistic forms and determining the literal, preferred, discourse-coherent meaning of sentences constitute a domain of language processing that relies on its own processing resource or working-memory system.

Adolescent↗
PubMed2000

The relationship between measures of working memory and sentence comprehension in patients with Alzheimer's disease.

Patients with dementia of the Alzheimer's type (DAT) and age- and education-matched older volunteers were tested on a battery of working memory tests, as well as on two tests of sentence comprehension. Patients had reduced spans and impaired central executive processes in working memory but showed normal effects of phonological and articulatory variables on span. On the sentence comprehension tasks, DAT patients showed effects of the number of propositions in a sentence but not of syntactic complexity. Impairment in the central executive processes of working memory in DAT patients was correlated with the effect of the number of propositions in a sentence on the sentence comprehension tasks. The results suggest that patients with DAT have working memory impairments that are related to their ability to map the meanings of sentences onto depictions of events in the world.

Aged↗
PubMed2000

Effects of gender marking in pronominal coindexation.

The naming latency of a pronoun was measured when a single previously presented name in a discourse either agreed or did not agree with the pronoun in gender and person. An effect of agreement was found both under conditions in which subjects were likely to have engaged in strategic processing of the pronoun (Experiment 1) and under conditions in which this was unlikely (Experiment 3). The effect of gender agreement was also investigated when two noun phrases were present in the discourse. The results continued to show an immediate effect of gender agreement (naming latencies increased when a pronoun did not agree with one of two previously presented nouns) under experimental conditions likely to engender strategic processing (Experiment 2). This last effect was not significant under experimental conditions that were not likely to engender strategic processing (Experiment 3). The results are discussed in terms of models of the process of identifying the referent of a pronoun in a discourse.

Adult↗
PubMed2000

Seroprevalence of Helicobacter pylori infection in cystic fibrosis and its cross-reactivity with anti-pseudomonas antibodies.

BACKGROUND: The prevalence of Helicobacter pylori infection and its role in gastroduodenal disease in cystic fibrosis (CF) are controversial. Additionally, serologic determination of infection in this population may be inaccurate because of cross-reactivity with other bacterial species. The seroprevalence of H. pylori in a cohort of patients with CF and its cross-reactivity with Pseudomonas antibodies were investigated. METHODS: A research enzyme-linked immunosorbent assay (ELISA), and three commercial serologic assays (PyloriStat; BioWhittaker, Walkersville, MD, U.S.A.; Flexsure; SmithKline Diagnostics, Inc., San Jose, CA, U.S.A.; and HM-CAP; EPI, Stony Brook, NY, U.S.A.) at three independent laboratories determined the seroprevalence of anti-H. pylori IgG antibodies in 70 patients with CF. Cross-reactivity between solid-phase H. pylori antigens and Pseudomonas antibodies was ascertained by a competitive inhibition assay, preadsorbing sera of patients with CF with whole cell proteins from different Pseudomonas species, and serum reanalysis by each assay. Western blot analysis before and after adsorption was performed to identify potential cross-reactive antigens. RESULTS: The research ELISA, Flexsure, Pyloristat, and HM-CAP initially showed H. pylori seropositivity of 47%, 28%, 24%, and 37%, respectively. Postadsorption seropositivity declined to 8%, 0%, 0%, and 15%, respectively. All patients with research ELISA true-positive results were confirmed endoscopically to have H. pylori infection. Western blot analysis showed a 31-kDa H. pylori protein with antigenic epitopes common to both bacterial species. CONCLUSIONS: Cross-reactivity between solid-phase H. pylori antigens and anti-Pseudomonas antibodies occurs in patients with CF. A high index of suspicion should be assumed in evaluating results of serologic H. pylori tests in this population. Preadsorption of CF sera with Pseudomonas proteins should be used in serologic testing.

Adolescent↗
PubMed2000

Activation of Broca's area by syntactic processing under conditions of concurrent articulation.

Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) when 11 subjects made plausibility judgments about written sentences that varied in their syntactic complexity. While making their judgments, subjects uttered the word "double" aloud at a rate of one utterance per second to inhibit their ability to rehearse the sentences. Blood flow increased in Broca's area when subjects made judgments about the more complex sentences. This result replicates and extends previous findings that blood flow increases in this region when subjects process complex syntax under no interference conditions. The results of this experiment provide strong evidence that the increase in blood flow seen in Broca's area in association with processing syntactically complex structures is not due to subvocal rehearsal of those structures, but rather results from processing syntactic forms themselves.

Adult↗
PubMed1999

PET studies of syntactic processing with auditory sentence presentation.

Sixteen subjects made plausibility judgments regarding auditorily presented cleft object and cleft subject sentences (It was the actress that the award thrilled; It was the award that thrilled the actress). rCBF increased in Broca's area, pars triangularis, when subjects processed the syntactically more complex cleft object sentences. The results are consistent with previous experiments using written materials and suggest that an increase in rCBF in Broca's area is associated with processing syntactically more complex sentences.

Adult↗
PubMed1999

Processing of visually presented sentences in Mandarin and English studied with fMRI.

Comprehension of visually presented sentences in fluent bilinguals was studied with functional magnetic resonance imaging (fMRI) using a set of conceptually similar sentences in two orthographically and phonologically distinct languages, Mandarin and English. Responses were monitored during scanning. Sentence comprehension in each language was compared to fixation in nine subjects and Tamil-like pseudo-word strings in five subjects. Spatially congruent activations in the prefrontal, temporal, and superior parietal regions and in the anterior supplementary motor area were observed for both languages and in both experiments at the individual and group levels of analysis. Proficient bilinguals exposed to both languages early in life utilize common neuroanatomical regions during the conceptual and syntactic processing of written language irrespective of their differences in surface features.

Adolescent↗
PubMed1999

Verbal working memory and sentence comprehension.

This target article discusses the verbal working memory system used in sentence comprehension. We review the concept of working memory as a short-duration system in which small amounts of information are simultaneously stored and manipulated in the service of accomplishing a task. We summarize the argument that syntactic processing in sentence comprehension requires such a storage and computational system. We then ask whether the working memory system used in syntactic processing is the same as that used in verbally mediated tasks that involve conscious controlled processing. Evidence is brought to bear from various sources: the relationship between individual differences in working memory and individual differences in the efficiency of syntactic processing; the effect of concurrent verbal memory load on syntactic processing; and syntactic processing in patients with poor short-term memory, patients with poor working memory, and patients with aphasia. Experimental results from these normal subjects and patients with various brain lesions converge on the conclusion that there is a specialization in the verbal working memory system for assigning the syntactic structure of a sentence and using that structure in determining sentence meaning that is separate from the working memory system underlying the use of sentence meaning to accomplish other functions. We present a theory of the divisions of the verbal working memory system and suggestions regarding its neural basis.

Cognition↗
PubMed1999

Knowledge of physician prescriptions and adherence to treatment among children with cystic fibrosis and their mothers.

This investigation examined factors related to adherence to treatment regimens for children with cystic fibrosis (CF) and their mothers. Subjects were 45 children with CF who ranged in age from 6 to 10 years and their mothers. Findings revealed that children's and parents' reports of level of adherence were related to their knowledge of the specific details associated with medically prescribed treatments. In this sample, 12% to 32% of mothers did not have an accurate understanding of physician recommendations for their children's treatments. When controlling for individual differences in the prescribed treatment regimens, parents' and children's knowledge of what had been prescribed accounted for a significant portion of the variance in the children's reported treatment-related behaviors. Results are discussed in terms of implications for future intervention research aimed at enhancing adherence to treatment as well as for future directions for clinical efforts in this area.

Attitude to Health↗
PubMed1999

The ketogenic diet for intractable epilepsy in adults: preliminary results.

PURPOSE: Little is known concerning the efficacy and adverse effects of the ketogenic diet in adults with refractory epilepsy. This review reports preliminary results in 11 adults prospectively treated with the diet who had previously failed to gain seizure control with two or more medications and/or surgery. METHODS: Eleven patients nine women, two men), median age, 32.2 years (range, 19-45 years) were treated with the ketogenic diet with a 4:1 ratio with fluid restriction. Six patients had symptomatic partial epilepsy, and five had symptomatic generalized epilepsy. The diet was administered in addition to antiepileptic medication by a multidisciplinary team geared exclusively to adult patients. Medications were not changed while on the diet. Seizure frequency at 8-month follow-up was compared with frequency during a baseline period. RESULTS: At 8 months of follow-up, three patients had a 90% seizure decrease, three patients had a 50-89% decrease in seizure frequency, one patient had <50% seizure decrease, and four patients discontinued the diet. Of the four patients who discontinued the diet, two had no appreciable change in their seizures despite high ketone levels. Two patients were unable to maintain persistent ketosis at home, despite having done so in the hospital. All seizure types responded to the diet. Common adverse effects included constipation and menstrual irregularities in women. Most patients reported a subjective improvement in concentration. Serum cholesterol and triglycerides increased while on the diet as well as cholesterol high-density lipoprotein (HDL) ratios. CONCLUSIONS: The ketogenic diet shows promise in both adult generalized and partial epilepsy. Persistent ketosis was possible in adults, and the diet was tolerable for most patients. Further study assessing the efficacy of the ketogenic diet, and the cognitive and long-term effects is ongoing.

Adult↗