Showing papers by "University of Toronto published in 1991"
TL;DR: It is concluded that recent theories placing the explanatory weight on parallel processing of the irrelevant and the relevant dimensions are likely to be more sucessful than are earlier theories attempting to locate a single bottleneck in attention.
Abstract: The literature on interference in the Stroop Color-Word Task, covering over 50 years and some 400 studies, is organized and reviewed. In so doing, a set of 18 reliable empirical finding is isolated that must be captured by any successful theory of the Stroop effect. Existing theoretical positions are summarized and evaluated in view of this critical evidence and the 2 major candidate theories ―relative speed of processing and automaticity of reading― are found to be wanting. It is concluded that recent theories placing the explanatory weight on parallel processing of the irrelevant and the relevant dimensions are likely to be more sucessful than are earlier theories attempting to locate a single bottleneck in attention
5,172 citations
TL;DR: A new supervised learning procedure for systems composed of many separate networks, each of which learns to handle a subset of the complete set of training cases, which is demonstrated to be able to be solved by a very simple expert network.
Abstract: We present a new supervised learning procedure for systems composed of many separate networks, each of which learns to handle a subset of the complete set of training cases. The new procedure can be viewed either as a modular version of a multilayer supervised network, or as an associative version of competitive learning. It therefore provides a new link between these two apparently different approaches. We demonstrate that the learning procedure divides up a vowel discrimination task into appropriate subtasks, each of which can be solved by a very simple expert network.
4,338 citations
TL;DR: The cloning of a gene that encodes a dopamine receptor gene that has high homology to the human dopamine D2 and D3 receptor genes is reported, which suggests the existence of other types of dopamine receptors which are more sensitive to clozapine.
Abstract: DOPAMINE receptors belong to the family of G protein-coupled receptors. On the basis of the homology between these receptors, three different dopamine receptors (D1,D2,D3) have been cloned1–7. Dopamine receptors are primary targets for drugs used in the treatment of psychomotor disorders such as Parkinson's disease and schizophrenia8,9. In the management of socially withdrawn and treatment-resistant schizophrenics, clozapine10 is one of the most favoured antipsychotics because it does not cause tardive dyskinesia11. Clozapine, however, has dissociation constants for binding to D2 and D3 that are 4 to 30 times the therapeutic free concentration of clozapine in plasma water12,13. This observation suggests the existence of other types of dopamine receptors which are more sensitive to clozapine. Here we report the cloning of a gene that encodes such a receptor (D4). The D4 receptor gene has high homology to the human dopamine D2 and D3 receptor genes. The pharmacological characteristics of this receptor resembles that of the D2 and D3 receptors, but its affinity for clozapine is one order of magnitude higher. Recognition and characterization of this clozapine neuroleptic site may prove useful in the design of new types of drugs.
2,027 citations
TL;DR: In this paper, the authors proposed a solution based on the theory of the excursion sets of F(r, R sub f), the four-dimensional initial density perturbation field smoothed with a continuous hierarchy of filters of radii.
Abstract: It is pointed out that most schemes for determining the mass function of virialized objects from the statistics of the initial density perturbation field suffer from the cloud-in-cloud problem of miscounting the number of low-mass clumps, many of which would have been subsumed into larger objects. The paper proposes a solution based on the theory of the excursion sets of F(r, R sub f), the four-dimensional initial density perturbation field smoothed with a continuous hierarchy of filters of radii R sub f.
1,826 citations
TL;DR: Evidence is presented to support the theory of secondary injury and the hypothesis that a key mechanism is posttraumatic ischemia with resultant infarction of the spinal cord and that it can be counteracted.
Abstract: In patients with spinal cord injury, the primary or mechanical trauma seldom causes total transection, even though the functional loss may be complete. In addition, biochemical and pathological changes in the cord may worsen after injury. To explain these phenomena, the concept of the secondary injury has evolved for which numerous pathophysiological mechanisms have been postulated. This paper reviews the concept of secondary injury with special emphasis on vascular mechanisms. Evidence is presented to support the theory of secondary injury and the hypothesis that a key mechanism is posttraumatic ischemia with resultant infarction of the spinal cord. Evidence for the role of vascular mechanisms has been obtained from a variety of models of acute spinal cord injury in several species. Many different angiographic methods have been used for assessing microcirculation of the cord and for measuring spinal cord blood flow after trauma. With these techniques, the major systemic and local vascular effects of acute spinal cord injury have been identified and implicated in the etiology of secondary injury. The systemic effects of acute spinal cord injury include hypotension and reduced cardiac output. The local effects include loss of autoregulation in the injured segment of the spinal cord and a marked reduction of the microcirculation in both gray and white matter, especially in hemorrhagic regions and in adjacent zones. The microcirculatory loss extends for a considerable distance proximal and distal to the site of injury. Many studies have shown a dose-dependent reduction of spinal cord blood flow varying with the severity of injury, and a reduction of spinal cord blood flow which worsens with time after injury. The functional deficits due to acute spinal cord injury have been measured electrophysiologically with techniques such as motor and somatosensory evoked potentials and have been found proportional to the degree of posttraumatic ischemia. The histological effects include early hemorrhagic necrosis leading to major infarction at the injury site. These posttraumatic vascular effects can be treated. Systemic normotension can be restored with volume expansion or vasopressors, and spinal cord blood flow can be improved with dopamine, steroids, nimodipine, or volume expansion. The combination of nimodipine and volume expansion improves posttraumatic spinal cord blood flow and spinal cord function measured by evoked potentials. These results provide strong evidence that posttraumatic ischemia is an important secondary mechanism of injury, and that it can be counteracted.
1,468 citations
TL;DR: Haplotyping suggests that the mutation in all five breeds of lean, heavily muscled swine has a common origin, and the development of a noninvasive diagnostic test will provide the basis for elimination of the MH gene or its controlled inclusion in swine breeding programs.
Abstract: Malignant hyperthermia (MH) causes neurological, liver, and kidney damage and death in humans and major economic losses in the swine industry. A single point mutation in the porcine gene for the skeletal muscle ryanodine receptor (ryr1) was found to be correlated with MH in five major breeds of lean, heavily muscled swine. Haplotyping suggests that the mutation in all five breeds has a common origin. Assuming that this is the causal mutation for MH, the development of a noninvasive diagnostic test will provide the basis for elimination of the MH gene or its controlled inclusion in swine breeding programs.
1,421 citations
11 Aug 1991
TL;DR: A formalization of chosen ciphertext attack is given in the model which is stronger than the "lunchtime attack" considered by Naor and Yung, and it is proved a non-interactive public-key cryptosystem based on non-Interactive zero-knowledge proof of knowledge to be secure against it.
Abstract: The zero-knowledge proof of knowledge, first denned by Fiat, Fiege and Shamir, was used by Galil, Haber and Yung as a means of constructing (out of a trapdoor function) an interactive public-key cryptosystem provably secure against chosen ciphertext attack. We introduce a revised setting which permits the definition of a non-interactive analogue, the non-interactive zero-knowledge proof of knowledge, and show how it may be constructed in that setting from a non-interactive zero-knowledge proof system for NP (of the type introduced by Blum, Feldman and Micali). We give a formalization of chosen ciphertext attack in our model which is stronger than the "lunchtime attack" considered by Naor and Yung, and prove a non-interactive public-key cryptosystem based on non-interactive zero-knowledge proof of knowledge to be secure against it.
1,198 citations
TL;DR: Most of the authors' familiar statistical methods, such as hypothesis testing, linear regression, analysis of variance, and maximum likelihood estimation, were designed to be implemented on mechanical calculators.
Abstract: Most of our familiar statistical methods, such as hypothesis testing, linear regression, analysis of variance, and maximum likelihood estimation, were designed to be implemented on mechanical calculators. Modern electronic computation has encouraged a host of new statistical methods that require fewer distributional assumptions than their predecessors and can be applied to more complicated statistical estimators. These methods allow the scientist to explore and describe data and draw valid statistical inferences without the usual concerns for mathematical tractability. This is possible because traditional methods of mathematical analysis are replaced by specially constructed computer algorithms. Mathematics has not disappeared from statistical theory. It is the main method for deciding which algorithms are correct and efficient tools for automating statistical inference.
1,185 citations
TL;DR: In long-term trials, low-GI diets result in modest improvements in overall blood glucose control in patients with insulin-dependent and non-insulin-dependent diabetes and the ability of low- GI diets to reduce insulin secretion and lower blood lipid concentrations in patientswith hypertriglyceridemia is of greater therapeutic importance.
1,180 citations
TL;DR: In this article, a review of the literature on goal setting through 1990 has been reviewed and integrated by Locke and Latham (1990a), with special emphasis on its practical implications for the motivation of employees in organizational settings.
1,138 citations
TL;DR: The cloning of a gene encoding a 477-amino-acid protein with strong homology to the cloned Dt receptor is reported here the existence of a dopamine D1-like receptor with these characteristics had not been predicted and may represent an alternative pathway for dopamine-mediated events and regulation of D2 receptor activity.
Abstract: Dopamine receptors belong to a superfamily of receptors that exert their biological effects through guanine nucleotide-binding (G) proteins. Two main dopamine receptor subtypes have been identified, D1 and D2, which differ in their pharmacological and biochemical characteristics. D1 stimulates adenylyl cyclase activity, whereas D2 inhibits it. Both receptors are primary targets for drugs used to treat many psychomotor diseases, including Parkinson's disease and schizophrenia. Whereas the dopamine D1 receptor has been cloned, biochemical and behavioural data indicate that dopamine D1-like receptors exist which either are not linked to adenylyl cyclase or display different pharmacological activities. We report here the cloning of a gene encoding a 477-amino-acid protein with strong homology to the cloned D1 receptor. The receptor, called D5, binds drugs with a pharmacological profile similar to that of the cloned D1 receptor, but displays a 10-fold higher affinity for the endogenous agonist, dopamine. As with D1, the dopamine D5 receptor stimulates adenylyl cyclase activity. Northern blot and in situ hybridization analyses reveal that the receptor is neuron-specific, localized primarily within limbic regions of the brain; no messenger RNA was detected in kidney, liver, heart or parathyroid gland. The existence of a dopamine D1-like receptor with these characteristics had not been predicted and may represent an alternative pathway for dopamine-mediated events and regulation of D2 receptor activity.
Journal Article•
TL;DR: Since the lexical chains are computable, and exist in non-domain-specific text, they provide a valuable indicator of text structure, and provide a semantic context for interpreting words, concepts, and sentences.
Abstract: In text, lexical cohesion is the result of chains of related words that contribute to the continuity of lexical meaning. These lexical chains are a direct result of units of text being "about the same thing," and finding text structure involves finding units of text that are about the same thing. Hence, computing the chains is useful, since they will have a correspondence to the structure of the text. Determining the structure of text is an essential step in determining the deep meaning of the text. In this paper, a thesaurus is used as the major knowledge base for computing lexical chains. Correspondences between lexical chains and structural elements are shown to exist. Since the lexical chains are computable, and exist in non-domain-specific text, they provide a valuable indicator of text structure. The lexical chains also provide a semantic context for interpreting words, concepts, and sentences.
TL;DR: The higher redox potential benzoquinones and naphthoquinones are the most cytotoxic presumably because of their higher electrophilicty and thiol reactivity and/or because the quinones or GSH conjugates are more readily reduced to semiquinones which activate oxygen.
TL;DR: This report was compiled on behalf of theStaff at the Northern General Hospital, Sheffield, the staff at the Royal Hallamshire Hospital,ffield, and the many people who helped at the scene.
Abstract: This report was compiled on behalf of the staff at the Northern General Hospital, Sheffield, the staff at the Royal Hallamshire Hospital, Sheffield, and the many people who helped at the scene. The efforts of hundreds of professionals and volunteers were vital and greatly appreciated. We thank Neil Appleyard, David Edbrooke, David Dawson, Stuart Yates, Ian Winston, John Duncan, G A Baker, Charlie Cooper, Kath Sherry, Tim Shaw, and A Moss for access to the neuropsychological reports on some of the survivors.
TL;DR: The semantics of revising knowledge bases represented by sets of propositional sentences is analyzed from a model-theoretic point of view and all revision schemes that satisfy the Gardenfors rationality postulates are characterized.
TL;DR: The authors formulate the deformable superquadrics which incorporate the global shape parameters of a conventional superellipsoid with the local degrees of freedom of a spline to form a novel class of dynamic models that can deform both locally and globally.
Abstract: The authors present a physically based approach to fitting complex three-dimensional shapes using a novel class of dynamic models that can deform both locally and globally. They formulate the deformable superquadrics which incorporate the global shape parameters of a conventional superellipsoid with the local degrees of freedom of a spline. The model's six global deformational degrees of freedom capture gross shape features from visual data and provide salient part descriptors for efficient indexing into a database of stored models. The local deformation parameters reconstruct the details of complex shapes that the global abstraction misses. The equations of motion which govern the behavior of deformable superquadrics make them responsive to externally applied forces. The authors fit models to visual data by transforming the data into forces and simulating the equations of motion through time to adjust the translational, rotational, and deformational degrees of freedom of the models. Model fitting experiments involving 2D monocular image data and 3D range data are presented. >
TL;DR: Clinical ultrasound biomicroscopy (UBM) has shown significant potential as an aid in diagnoses of ocular disease and the ability to define the relationship of the iris, posterior chamber, zonules, ciliary body, and lens is potentially helpful in understanding mechanisms of glaucoma.
01 Sep 1991
TL;DR: Investigation of the induction of extrathymic tolerance using BALB/c mice that were made tolerant to Staphylococcus aureus enterotoxin B indicates that a deletional mechanism can contribute to the induction in peripheral lymphoid cells.
Abstract: Clonal deletion and functional inactivation of self-reactive cells have been invoked as mechanisms underlying intrathymic development of T-cell tolerance. The relative importance of these mechanisms in the development of tolerance of more mature, peripheral T cells either to self or to exogenous antigens is unclear, although recent data relate the development of T-cell tolerance in the periphery to clonal anergy. We have now investigated the induction of extrathymic tolerance using BALB/c mice that were made tolerant to Staphylococcus aureus enterotoxin B, a superantigen which specifically interacts in such mice with T cells bearing V beta 8 antigen receptors. Both euthymic and athymic mice made tolerant to S. aureus enterotoxin B had a markedly reduced number of V beta 8.1,2+ CD4+ peripheral T cells. This reduction was accompanied by genomic DNA fragmentation that is associated with cell death. These results indicate that a deletional mechanism can contribute to the induction of T-cell tolerance in peripheral lymphoid cells.
TL;DR: It is concluded that sustained administration of desferrioxamine may slow the clinical progression of the dementia associated with AD.
TL;DR: Given the broad range of outcome among sexual abuse victims, as well as the methodological weaknesses present in many of the studies reviewed, it is not possible at this time to postulate the existence of a "post-sexual-abuse-syndrome" with a specific course or outcome.
TL;DR: In this paper, a recurrent connectionist network was trained to output semantic feature vectors when presented with letter strings, and when damaged, the network exhibited characteristics that resembled several of the phenomena found in deep dyslexia and semantic access dyslexias.
Abstract: A recurrent connectionist network was trained to output semantic feature vectors when presented with letter strings. When damaged, the network exhibited characteristics that resembled several of the phenomena found in deep dyslexia and semantic-access dyslexia. Damaged networks sometimes settled to the semantic vectors for semantically similar but visually dissimilar words. With severe damage, a forced-choice decision between categories was possible even when the choice of the particular semantic vector within the category was not possible. The damaged networks typically exhibited many mixed visual and semantic errors in which the output corresponded to a word that was both visually and semantically similar. Surprisingly, damage near the output sometimes caused pure visual errors. Indeed, the characteristic error pattern of deep dyslexia occurred with damage to virtually any part of the network.
TL;DR: Lignan production with the in vitro method related well to the urinary lignan excretion observed in rats and humans and should be useful in the estimation of lignans production from a given diet and in the formulation of high-lignan-producing diet for the purpose of reducing the cancer risk.
Abstract: Mammalian lignans such as enterolactone and enterodiol, which are produced in the colon from precursors in foods, have been suggested as playing a role in the cancer‐protective effect of vegetarian diets. Despite this, very little is known regarding the amount that is produced from different food products. Therefore, the objective of this study was to determine the production of mammalian lignans from 68 common plant foods by using the technique of in vitro fermentation with human fecal microbiota, which simulates colonic fermentation. Results showed a wide range (21–67,541 μg/100 g sample) in the amount of lignans produced. On the average as a group, the oilseeds produced the highest amounts (20,461 ± 12,685), followed by the dried seaweeds (900 ± 247), whole legumes (562 ± 211), cereal brans (486 ± 90), legume hulls (371 ± 52), whole grain cereals (359 ± 81), vegetables (144 ± 23), and fruits (84 ± 22). The vegetables produced the second highest concentration of lignans (1,546 ± 280) when the d...
TL;DR: The superior potency of BAPTA compared to EGTA apparently results from the faster calcium-binding kinetics of B APTA and suggests that the calcium- binding molecule that triggers release binds calcium in considerably less than 200 microsec and is located very close to calcium channels.
Abstract: A number of calcium buffers were examined for their ability to reduce evoked transmitter release when injected into the presynaptic terminal of the squid giant synapse. Injection of EGTA was virtually ineffective at reducing transmitter release, even at estimated intracellular concentrations up to 80 mM. Conversely, the buffer 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), which has an equilibrium affinity for calcium similar to that of EGTA at pH 7.2, produced a substantial reduction in transmitter release when injected presynaptically. This effect of BAPTA was reversible, presumably because the buffer diffused out of the terminal and into uninjected regions of the presynaptic axon. BAPTA derivatives with estimated intracellular calcium dissociation constants (Kd) ranging from 0.18 to 4.9 microM were effective at reducing transmitter release at similar estimated concentrations. A BAPTA derivative with an estimated intracellular Kd of 31 mM was less effective. BAPTA did not affect presynaptic action potentials or calcium spikes in ways that could explain its ability to reduce transmitter release. The relative effects of presynaptic injections of BAPTA and derivatives are consistent with the calcium-buffering capability of these compounds if the presynaptic calcium transient that triggers release is hundreds of microM or larger. The superior potency of BAPTA compared to EGTA apparently results from the faster calcium-binding kinetics of BAPTA and suggests that the calcium-binding molecule that triggers release binds calcium in considerably less than 200 microsec and is located very close to calcium channels.
TL;DR: Subjects who expressed a fear of falling were found to exhibit significantly poorer performance in blindfolded spontaneous-sway tests and in eyes-open, one-leg stance tests, and the clinical scale was the only balance measure that showed a significant association with retrospective, self-reported falling history.
Abstract: A cross-sectional study was performed to investigate the association between fear of falling and postural performance in the elderly. One hundred ambulatory and independent volunteers (aged 62-96) were subjected to five types of balance tests: (a) spontaneous postural sway, (b) induced anterior-posterior sway, (c) induced medial-lateral sway, (d) one-leg stance, and (e) a clinical balance assessment scale. Pseudorandom platform motions were used in the induced-sway tests. The subjects were classified into both "faller"/"nonfaller" and "fear"/"no-fear" categories, to allow the influence of fear of falling and falling history to be separated in the analyses. Subjects who expressed a fear of falling were found to exhibit significantly poorer performance in blindfolded spontaneous-sway tests and in eyes-open, one-leg stance tests. The clinical scale was the only balance measure that showed a significant association with retrospective, self-reported falling history. We could not ascertain whether the fear of falling affected balance-test performance in an artifactual manner, or whether the fear and poorer performance were related to a true deterioration in postural control. Until this issue can be resolved, balance-test performance should be interpreted with caution when testing apprehensive individuals. Furthermore, studies of postural control and falling should allow for the potentially confounding influence of fear of falling.
Journal Article•
TL;DR: In this paper, a single-blind study was conducted to investigate whether the progression of dementia could be slowed by the trivalent ion chelator, desferrioxamine.
Abstract: Although epidemiological and biochemical evidence suggests that aluminium may be associated with Alzheimer's disease (AD), there is no convincing proof of a causal link for aluminium in disease progression. We have completed a two year, single-blind study to investigate whether the progression of dementia could be slowed by the trivalent ion chelator, desferrioxamine. 48 patients with probable AD were randomly assigned to receive desferrioxamine (125 mg intramuscularly twice daily, 5 days per week, for 24 months), oral placebo (lecithin), or no treatment. No significant differences in baseline measures of intelligence, memory, or speech ability existed between groups. Activities of daily living were assessed and videorecorded at 6, 12, 18, and 24 month intervals. There were no differences in the rate of deterioration of patients receiving either placebo or no treatment. Desferrioxamine treatment led to significant reduction in the rate of decline of daily living skills as assessed by both group means (p = 0.03) and variances (p less than 0.04). The mean rate of decline was twice as rapid for the no-treatment group. Appetite (n = 4) and weight (n = 1) loss were the only reported side-effects. We conclude that sustained administration of desferrioxamine may slow the clinical progression of the dementia associated with AD.
TL;DR: In this paper, the authors reviewed past research examining group cohesion and performance using metaanalysis and found a positive relationship with the average cohesive group performing 18 percentile points above the average non-cohesive group.
Abstract: Past research examining group cohesion and performance was reviewed using metaanalysis. The results indicated a positive relationship with the average cohesive group performing 18 percentile points above the average noncohesive group. Given the nature of the studies used here (all studies had been previously published), caution is suggested in generalizing these results to "real" work groups.
TL;DR: In this paper, a stylized view of individual consumer choice decision-making is presented for the study of many marketing decisions, and the authors discuss whether consideration sets really exist and, if so, the factors that affect their composition, structure, and role in decision making.
Abstract: This paper affords a stylized view of individual consumer choice decision-making appropriate to the study of many marketing decisions. It summarizes issues relating to consideration set effects on consumer judgment and choice. It discusses whether consideration sets really exist and, if so, the factors that affect their composition, structure, and role in decision-making. It examines some new developments in the measurement and modeling of consideration set effects on decision-making. The paper concludes with suggestions for needed research.
TL;DR: Although an internal amino acid sequence homology could be detected between the two halves of the predicted polypeptide, the lack of alignment of the nucleotide sequence as well as the different positions of the exon/intron boundaries does not seem to support the hypothesis of a recent gene duplication event.
TL;DR: Results are further evidence that the cystic fibrosis transmembrane regulator is a Cl- channel which can be activated by specific phosphorylation events and inactivated by dephosphorylation; they reveal an unsuspected synergism between converging kinase regulatory pathways.
Abstract: A cyclic AMP-stimulated chloride conductance appears when the cystic fibrosis gene is expressed in non-epithelial cells by infection with recombinant viruses. Cyclic AMP-stimulated conductance in this system is mediated by the same ohmic, low-conductance Cl- channel as in human secretory epithelia, but control of this channel by phosphorylation has not been directly demonstrated. Here we report the appearance of the low-conductance Cl- channel in Chinese hamster ovary cells after stable transfection with the cystic fibrosis gene. The channel is regulated on-cell by membrane-permeant analogues of cAMP and off-cell by protein kinases A and C and by alkaline phosphatase. These results are further evidence that the cystic fibrosis transmembrane regulator is a Cl- channel which can be activated by specific phosphorylation events and inactivated by dephosphorylation; they reveal an unsuspected synergism between converging kinase regulatory pathways.