Showing papers by "McGill University published in 1989"

A Distributed, Developmental Model of Word Recognition and Naming.

Abstract: A parallel distributed processing model of visual word recognition and pronunciation is described. The model consists of sets of orthographic and phonological units and an interlevel of hidden units. Weights on connections between units were modified during a training phase using the back-propagation learning algorithm. The model simulates many aspects of human performance, including (a) differences between words in terms of processing difficulty, (b) pronunciation of novel items, (c) differences between readers in terms of word recognition skill, (d) transitions from beginning to skilled reading, and (e) differences in performance on lexical decision and naming tasks. The model's behavior early in the learning phase corresponds to that of children acquiring word recognition skills. Training with a smaller number of hidden units produces output characteristic of many dyslexic readers. Naming is simulated without pronunciation rules, and lexical decisions are simulated without accessing word-level representations. The performance of the model is largely determined by three factors: the nature of the input, a significant fragment of written English; the learning rule, which encodes the implicit structure of the orthography in the weights on connections; and the architecture of the system, which influences the scope of what can be learned.

A History of Archaeological Thought

Abstract: In its original edition, Bruce Trigger's book was the first ever to examine the history of archaeological thought from medieval times to the present in world-wide perspective. Now, in this new edition, he both updates the original work and introduces new archaeological perspectives and concerns. At once stimulating and even-handed, it places the development of archaeological thought and theory throughout within a broad social and intellectual framework. The successive but interacting trends apparent in archaeological thought are defined and the author seeks to determine the extent to which these trends were a reflection of the personal and collective interests of archaeologists as these relate - in the West at least - to the fluctuating fortunes of the middle classes. While subjective influences have been powerful, Professor Trigger argues that the gradual accumulation of archaeological data has exercised a growing constraint on interpretation. In turn, this has increased the objectivity of archaeological research and enhanced its value for understanding the entire span of human history and the human condition in general.

Differential effects of fornix and caudate nucleus lesions on two radial maze tasks: evidence for multiple memory systems.

Abstract: The present experiments were designed to examine the hypothesis that the mammalian brain contains anatomically distinct memory systems. Rats with bilateral lesions of caudate nucleus or fimbria-fornix and a control group were tested postoperatively on 1 of 2 versions of the radial maze task. In a standard win-shift version, each of the 8 arms of the maze was baited once, and the number of errors (revisits) in the first 8 choices of each trial was recorded. Fimbria-fornix rats were impaired in choice accuracy, while caudate animals were unimpaired relative to controls. Different groups of rats with similar lesions were tested on a newly developed win-stay version of the radial maze, in which the location of 4 randomly selected baited arms was signaled by a light at the entrance to each arm, and which required rats to revisit arms in which reinforcement had been previously acquired within a trial. Rats with fimbria-fornix lesions were superior to controls in choice accuracy on the win-stay radial maze task, while caudate animals were impaired relative to controls. The results demonstrate a double dissociation of the mnemonic functions of the hippocampus and caudate nucleus. Some implications of the presence of 2 memory systems in the mammalian brain are discussed.

The statistical analysis of mitochondrial DNA polymorphisms: chi 2 and the problem of small samples.

Abstract: Significance levels obtained from a x2 contingency test are suspect when sample sizes are small. Traditionally this has meant that data must be combined. However, such an approach may obscure heterogeneity and hence potentially reduce the power of the statistical test. In this paper, we present a Monte Carlo solution to this problem: by this method, no lumping of data is required, and the accuracy of the estimate of c1 (i.e., a type 1 error) depends only on the number of randomizations of the original data set. We illustrate this technique with data from mtDNA studies, where numerous genotypes are often observed and sample sizes are relatively small.

Mental rotation of the neuronal population vector.

Abstract: A rhesus monkey was trained to move its arm in a direction that was perpendicular to and counterclockwise from the direction of a target light that changed in position from trial to trial. Solution of this problem was hypothesized to involve the creation and mental rotation of an imagined movement vector from the direction of the light to the direction of the movement. This hypothesis was tested directly by recording the activity of cells in the motor cortex during performance of the task and computing the neuronal population vector in successive time intervals during the reaction time. The population vector rotated gradually counterclockwise from the direction of the light to the direction of the movement at an average rate of 732 degrees per second. These results provide direct, neural evidence for the mental rotation hypothesis and indicate that the neuronal population vector is a useful tool for "reading out" and identifying cognitive operations of neuronal ensembles.

Rethinking the concept of user involvement

Abstract: Within the field of information systems, user involvement generally refers to participation in the systems development process by potential users of their representatives and is measured as a set of behaviors or activities that such individuals perform. This article argues for a separation of the constructs of user participation (a set of behaviors or activities performed by users in the system development process) and user involvement (a subjective psychological state reflecting the importance and personal relevance of a system to the user). Such a distinction is not only more consistent with conceptualizations of involvement found in other disciplines, but it also leads to a number of new and interesting hypotheses. These hypotheses promise a richer theoretical network that describes the role and importance of participation and involvement in the implementation process.

Universal Grammar and second language acquisition

Abstract: This book explores the relationship between linguistic universals and second language acquisition. Although no knowledge of generative grammar is presupposed, the theoretical framework underlying the work is the principles and parameters approach to Universal Grammar (UG), as realized in Chomsky's Government and Binding theory. In recent research, the question has arisen as to whether the principles and parameters of UG remain available in language acquisition that is non-primary. Within second language acquisition theorizing, hypotheses have ranged from UG playing no role at all to UG operating exactly as in primary language acquisition. In this work the theoretical arguments and data from the whole spectrum are reviewed.

Receiver operating characteristic (ROC) methodology: the state of the art.

Abstract: Receiver operating characteristic (ROC) methodology has been increasingly used in medical applications in the last 10 years. The text by Swets and Pickett has popularized the technique and the journal Medical Decision Making (1981--) provides a forum for further methodologic issues. In this article, I will (1) describe the nature of the data generated by ROC studies; (2) evaluate the choices of summary indices of performance (accuracy); (3) outline the data-analytic techniques used, and how to incorporate data from multiple observers and multiple "readings"; (4) review proposed alternatives to the commonly used binormal ROC model; and (5) discuss issues, such as verification bias, and challenges, such as multicenter comparative imaging studies and the difficulty of obtaining "truth data", which need to be addressed when adapting ROC methods to medical contexts.

Visionary leadership and strategic management

Abstract: This paper describes the concept of visionary leadership in a new way, more suitable for strategic management. First, drawing on an account of theatre, it presents a model of visionary leadership as drama, an interaction of repetition, representation, and assistance. Second, considering the experiences of a number of visionary leaders, in terms of style, process, content, and context, the paper describes various types of visionary leadership—the creator, the proselytizer, the idealist, the bricoleur, and the diviner.

The immune-hypothalamic-pituitary-adrenal axis.

Abstract: IN VERTEBRATES, four major systems of intercellular communication exist: the neural, the endocrine, the neuroendocrine, and the immune system. For many years evidence has accumulated linking the neural, the endocrine, and the neuroendocrine systems, but the immune system was often viewed as essentially autonomous. The enormous recent increase in our knowledge of how the immune system is regulated has led many scientists to postulate that this autonomy may be more apparent than real: that the immune system is subject to endocrine and neural control, and that it exerts, in turn, a reciprocal effect on neuroendocrine systems. In this review we intend to examine the interactions between the immune system and the hypothalamic-pituitary-adrenal (HPA) axis. In the first part of the review we will discuss products and components from the immune system that stimulate or inhibit the HPA axis. These include monokines and lymphokines, i.e. the regulatory secretions of the immune system, and other peptides such as ACT...

Trace inference, curvature consistency, and curve detection

Abstract: An approach is described for curve inference that is based on curvature information. The inference procedure is divided into two stages: a trace inference stage, which is the subject of the present work, and a curve synthesis stage. It is shown that recovery of the trace of a curve requires estimating local models for the curve at the same time, and that tangent and curvature information are sufficient. These make it possible to specify powerful constraints between estimated tangents to a curve, in terms of a neighborhood relationship called cocircularity, and between curvature estimates, in terms of a curvature consistency relation. Because all curve information is quantized, special care must be taken to obtain accurate estimates of trace points, tangents, and curvatures. This issue is addressed specifically to the introduction of a smoothness constraint and a maximum curvature constraint. The procedure is applied to two types of images: artificial images designed to evaluate curvature and noise sensitivity, and natural images. >

Early Bilingual Development: One Language or Two?.

Abstract: It is commonly thought that children learning two languages simultaneously during infancy go through a stage when they cannot differentiate their two languages. Virtually all studies of infant bilingual development have found that bilingual children mix elements from their two languages. These results have been interpreted as evidence for a unitary, undifferentiated language system (the unitary language system hypothesis). The empirical basis for these claims is re-examined and it is argued that, contrary to most extant interpretations, bilingual children develop differentiated language systems from the beginning and are able to use their developing languages in contextually sensitive ways. A call for more serious attention to the possible role of parental input in the form of mixed utterances is made.

Neonatal handling alters adrenocortical negative feedback sensitivity and hippocampal type II glucocorticoid receptor binding in the rat.

Abstract: Adult rats handled (H) daily for the first 3 weeks of life show a dramatically altered adrenocortical response to stress. We found that H animals secreted less ACTH and corticosterone (B) during and following the termination of stress than did nonhandled (NH) controls. In contrast, H and NH animals did not differ in basal B secretion at any point in the diurnal cycle, nor in adrenocortical responses to exogenously administered oCRF or ACTH. Moreover, the clearance rate for B was similar in H and NH animals. H animals were more sensitive than NH animals to the inhibitory effects of either B or dexamethasone on stress-induced adrenocortical activity. In a dose-response study, both glucocorticoids administered 3 h prior to testing suppressed the adrenocortical response to a 20-min restraint stress to a greater extent in the H animals. Handling increased type II, glucocorticoid receptor binding capacity in the hippocampus of adult animals (approximately 50% increase in capacity, with no change in affinity). There were no handling-induced changes in type II receptor binding capacity in the hypothalamus or pituitary, nor in type I receptor binding capacity in the hippocampus. Following chronic (5 mg/kg/day) treatment with B, hippocampal type II receptor binding capacity was significantly reduced in the B-treated H animals, compared with saline-treated H animals, and indistinguishable from saline-treated NH animals. Down-regulated H animals, like NH animals, hypersecreted B following the termination of stress in comparison to the saline-treated H animals.(ABSTRACT TRUNCATED AT 250 WORDS)

The Canadian Neurological Scale Validation and reliability assessment

Abstract: The Canadian Neurological Scale (CNS) was designed to monitor mentation and motor functions in stroke patients. We assessed its validity and reliability on a group of 157 patients with a diagnosis of acute cerebrovascular accident. We determined validity by (1) correlating scale items and total score with the standard neurologic examination; (2) exploring the scale's predictive power with different end points at 6 months--the initial CNS was a significant predictor of outcome; (3) showing that the CNS had higher correlation coefficients with the initial neurologic examination than the Glasgow Coma Scale; and (4) assessing the responsiveness of the scale to change in the neurologic status of stroke patients. Interobserver reliability, measured by kappa statistics on each scale item, was good. Accordingly, we established the validity and reliability of the CNS for its use in clinical studies and in the care of stroke patients.

Cross-cultural Interaction: The International Comparison Fallacy?

Abstract: Joint ventures, mergers and acquisitions, licensing and distribution agreements, and sales of products and services—crucial aspects of all such interorganizational relationships, are face-to-face negotiations. As the proportion of foreign to domestic trade increases, so does the frequency of business negotiations between people from different countries and cultures. Perlmutter estimates that over 50% of an international manager’s time is spent negotiating.1 To successfully manage these negotiations, businesspeople need to know how to influence and communicate with members of cultures other than their own.

Evaluating the fractal dimension of profiles

Abstract: There are many definitions of the fractal dimension of an object, including box dimension, Bouligand-Minkowski dimension, and intersection dimension. Although they are all equivalent in the continuous domain, they differ substantially when discretized and applied to digitized data. We show that the standard implementations of these definitions on self-affine curves with known fractal dimension (Weierstrass-Mandelbrot, Kiesswetter, fractional Brownian motion) yield results with significant errors. An analysis of the source of these errors leads to a new algorithm in one dimension, called the variation method, which yields accurate results. The variation method uses the notion of \ensuremath{\epsilon} oscillation to measure the amplitude of the one-dimensional function in an \ensuremath{\epsilon} neighborhood. The order of growth of the integral of the \ensuremath{\epsilon} oscillation (called the \ensuremath{\epsilon} variation), as \ensuremath{\epsilon} tends toward zero, is directly related to the fractal dimension. In this paper, we present the variation method for one-dimensional (1D) profiles and show that, in the limit, it is equivalent to the classical box-counting method. The result is an algorithm for reliably estimating the fractal dimension of 1D profiles; i.e., graphs of functions of a single variable. The algorithm is tested on profiles with known fractal dimension.

A Conceptual Framework for the Integration of Language and Content in Second/Foreign Language Instruction

Abstract: This article proposes a conceptual framework for the integration of language and content teaching in second and foreign language classrooms. In this model, language and content teachers work collaboratively to determine language-teaching objectives. These objectives derive from two considerations: (a) content-obligatory language (language essential to an understanding of content material) and (b) content-compatible language (language that can be taught naturally within the context of a particular subject matter and that students require additional practice with). The conceptual framework is illustrated in four instructional settings—the mainstream class, the ESL class, the foreign language immersion class, and the FLES (Foreign Language in the Elementary School) class. General implications for the integration of language and content teaching are also discussed.

Cholecystokinin tetrapeptide induces panic-like attacks in healthy volunteers. Preliminary findings.

Abstract: • A total of 31 intravenous injections of the tetrapeptide cholecystokinin (30-33) were carried out in ten healthy subjects. In seven subjects, cholecystokinin-4 provoked a short-lasting (one to four minutes) panic-like attack (an intense unexplainable fear) at doses between 20 and 100 μg. In the other three subjects, doses of 80 to 100 μ induced severe anxiety, but no panic-like attack. All subjects experienced severe gastrointestinal symptoms. Pretreatment with lorazepam, but not with meprobamate or naloxone, prevented the psychic effects of cholecystokinin-4 in subjects who had experienced a panic-like attack with the same dose of this peptide. Following the peptide injection, levels of plasma free catecholamines, lactate, and glucose were unchanged, whereas levels of plasma cortisol and prolactin were increased. The intravenous injection of the sulfated cholecystokinin octapeptide (26-33) in two subjects (doses of 35 and 40 μg, respectively) produced severe gastrointestinal symptoms, but failed to induce any anxiety or panic-like attacks. These preliminary findings suggest that cholecystokinin-4 may have a panicinducing effect. It remains to be established if this peptide exerts this effect via a direct activation of central cholecystokinin receptors.

Immunohistochemical detection and immunochemical analysis of type II collagen degradation in human normal, rheumatoid, and osteoarthritic articular cartilages and in explants of bovine articular cartilage cultured with interleukin 1.

Abstract: Articular cartilage destruction and loss of function in arthritic diseases involves proteolytic degradation of the connective tissue matrix. We have investigated the degradation of cartilage collagen by developing immunochemical methods that permit the identification and analysis of type II collagen degradation in situ. Previously, a technique to specifically identify type II collagen degradation in situ in articular cartilage did not exist. These methods utilize a polyclonal antiserum (R181) that specifically reacts with unwound alpha-chains and CNBr-derived peptides, alpha 1(II)CB11 and alpha 1(II)CB8, of human and bovine type II collagens. The experimental approach is based on the fact that when fibrillar collagens are cleaved the helical collagen molecule unwinds, exposing hidden epitopes. Here we demonstrate the use of R181 in studying type II collagen degradation in bovine articular cartilage that has been cultured with or without IL-1 and in human normal, rheumatoid, and osteoarthritic articular cartilages. Compared to cartilages either freshly isolated or cultured without IL-1, bovine cartilage cultured with IL-1 for 3-5 d showed an increase in both pericellular and intercellular immunohistochemical staining. Extracts of these cartilages contained type II collagen alpha chains that were increased in amount after culture with IL-1 for 11 d. In addition, culture with IL-1 resulted in the appearance of alpha chain fragments of lower molecular weight. All human arthritic tissues examined showed areas of pronounced pericellular and territorial staining for collagen degradation as compared with non-diseased tissues, indicating that chondrocytes are responsible in part for this degradation as compared with non-diseased tissues. In most cases rheumatoid cartilage was stained most intensely at the articular surface and in the deep and mid-zones, whereas osteoarthritic cartilage usually stained more in the superficial and mid-zones, but less intensely. Distinct patterns of sites of collagen degradation reflect differences in collagen destruction in these diseases, suggesting possible different sources of chondrocyte activation. These experiments demonstrate the application of immunological methods to detect collagen degradation and demonstrate an increase of collagen degradation in human arthritides and in IL-1-treated viable bovine cartilage.

Discrete mutations introduced in the predicted nucleotide-binding sites of the mdr1 gene abolish its ability to confer multidrug resistance.

Abstract: In cells stably transfected and overexpressing the mouse mdr1 gene, multidrug resistance is associated with an increased ATP-dependent drug efflux. Analysis of the predicted amino acid sequence of the MDR1 protein revealed the presence of two putative nucleotide-binding sites (NBS). To assess the functional importance of these NBS in the overall drug resistance phenotype conferred by mdr1, we introduced amino acid substitutions in the core consensus sequence for nucleotide binding, GXGKST. Mutants bearing the sequence GXAKST or GXGRST at either of the two NBS of mdr1 and a double mutant harboring the sequence GXGRST at both NBS were generated. The integrity of the two NBS was essential for the biological activity of mdr1, since all five mutants were unable to confer drug resistance to hamster drug-sensitive cells in transfection experiments. Conversely, a lysine-to-arginine substitution outside the core consensus sequence had no effect on the activity of mdr1. Failure to reduce intracellular accumulation of [3H]vinblastine paralleled the loss of activity in cell clones expressing mutant MDR1 proteins. However, the ability to bind the photoactivatable ATP analog 8-azido ATP was retained in the five inactive MDR1 mutants. This result implies that an essential step subsequent to ATP binding is impaired in these mutants, possibly ATP hydrolysis or secondary conformational changes induced by ATP-binding or hydrolysis. Our results suggest that the two NBS function in a cooperative fashion, since mutations in a single NBS completely abrogated the biological activity of mdr1.

Leadership: The Art of Empowering Others

Abstract: I n his handbook, The Prince, Machiavelli assures his readers some being aspiring leaders, no doubt that only by carefully amassing power and building a fearsome respect could one become a great leader. While the shadowy court life of 16th-century Italy demanded such treachery to ensure one's power, it seems hard to imagine Machiavelli's advice today as anything but a historical curiosity. Yet, interestingly, much of the management literature has focused on the strategies and tactics that managers can use to increase their own power and influence.' As such, a Machiavellian quality often pervades the literature, encouraging managers to ensure that their power base is strong and growing. At the same time a small but increasing number of management theorists have begun to explore the idea that organizational effectiveness also depends on the sharing of power that the distribution of power is more important than the hoarding of power.2 While the idea of making others feel more powerful contradicts the stereotype of the all-powerful executive, research suggests that the traditional ways of explaining a leader's influence may not be entirely correct. For example, recent leadership studies argue that the practice of empowering or instilling a sense of power is at the root of organizational effectiveness, especially during times of transition and transformation.3 In addition, studies of power and control within organizations indicate that the more productive forms of organizational power increase with superiors' sharing of power and responsibility with subordinates.4 And while there is an increasing awareness of this need for more empowering leadership, we have only recently started to see documentation about the actual practices that leaders employ to effectively build a sense of power among organizational members as well as the contexts most suited for empowerment practices.5 In this article, I will explore these practices further by drawing upon a recent study of senior executives who proved themselves highly effective leaders. They were selected by a panel of professors at the Harvard Business School and management consultants who were well acquainted with them and their companies. The study included eight chief executive officers and executive vice-presidents of Fortune 500 companies and successful entrepreneurial firms, representing industries as diverse as telecommunications, office automation, retail banking, beverages, packaged foods, and managementconsulting. In each case, these individuals were responsible for either the creation of highly successful companies or for performing what were described as remarkable turnarounds. During my study of these executives, I conducted extensive interviews, observed them on the job, read company and other documents, and talked with their colleagues and subordinates. While the study focused on the broader issue of leadership styles, intensive interviews with these executives and their subordinates revealed that many were characterized as empowering leaders. Their actions were perceived as building confidence and restoring a sense of personal power and self-efficacy during difficult organizational transitions. From this study, I identified certain organizational contexts of powerlessness and management practices derived to remedy them. In this article I will also illustrate several of these practices through a series of vignettes. While the reader may recognize some of the basic ideas behind these practices (such as providing greater opportunities for initiative), it is often the creative manner in which the leader deploys the particular practice that distinguishes them. The reader will discover how they have been carefully tailored to fit the context at hand. I might add, however, that these practices represent just a few of the broad repertoire of actions that leaders can take to make an empowering difference in their organizations.

Adaptation to seasonality in a cricket: patterns of phenotypic and genotypic variation in body size and diapause expression along a cline in season length.

Abstract: This paper investigates patterns of phenotypic variation in the striped ground cricket (Allonemobious fasciatus) along a cline in season length and tests the hypothesis that variation in body size and diapause propensity is the result of diversifying selection due to different local conditions. We examined 83 populations and found that A. fasciatus produced a single generation per year (univoltine) north of 37°N latitude and was bivoltine south of 35°30'N. Body size generally increased with increasing season length, with a sudden drop in the region corresponding to the transition from univoltine to bivoltine life cycles, reflecting the division of total season length in two within-bivoltine populations. We reared ten populations in our laboratory and found that much of the interpopulation variance in body size observed in the field could be attributed to genetic differences. Diapause expression also varied significantly among populations and was strongly correlated with season length. The heritability of body size did not differ between populations, but full-sib estimates greatly exceeded parent-offspring estimates (h po2=0.15±0.05; h fs2=0.45±0.04) suggesting that there are important nonadditive genetic effects. The heritability of diapause expression, determined from analysis of full sibs, varied significantly between populations (0.33 ± 0.10 to 1.31 ± 0.21) with an average of 0.74 ± 0.16. Body size and diapause expression were genetically correlated in transition-zone populations, but not in univoltine or bivoltine populations. Our findings support the suggestion that clinal variation in body size and diapause expression in the striped ground cricket reflect adaptation to season length.

Identification of a cDNA Encoding a Long Form of Prolactin Receptor in Human Hepatoma and Breast Cancer Cells

Abstract: Human PRL receptor cDNA clones from hepatoma (Hep G2) and breast cancer (T-47D) libraries were isolated by using a rat PRL receptor cDNA probe. The nucleotide sequence predicts a mature protein of 598 amino acids with a much longer cytoplasmic domain than the rat liver PRL receptor. Although this extended region has additional segments of localized sequence identity with the human GH receptor, there is no identity with any consensus sequences known to be involved in hormonal signal transduction. This cDNA will be a valuable tool to better understand the role of PRL in the development and growth of human breast cancer.

Occupational Exposures: Evidence for a Causal Association with Chronic Obstructive Pulmonary Disease

Abstract: The increase in morbidity and mortality attributable to chronic obstructive pulmonary disease (COPD) has focused attention on environmental and host factors causally associated with the clinical entities included under the rubric of this term with a view to early preventive intervention. Despite the biologic plausibility of inhaled agents being causally implicated, only the role of tobacco smoke has been accepted beyond doubt. However, evidence implicating occupational exposures has accumulated, in particular over the last 2 yr, from: (1) community-based studies (in which larger study populations provide greater power than the usually smaller workforce based studies); (2) longitudinal studies of lung function (which enhance the signal of interest, namely the effects of the occupational exposures, and diminish the noise due to between-individual differences); (3) pathology studies (in which the outcome of interest is the quantitative measurement of emphysema), and (4) cohort mortality studies of all or specific causes of death. This evidence, reviewed here according to accepted criteria for establishing causality, leaves little doubt that occupational exposure to dust and/or to dust and fumes may be causally implicated in the genesis of COPD. As with tobacco exposure, both bronchitis (mucus hypersecretion) and airflow limitation are recognized as causally related to exposure, but not necessarily to each other. As with tobacco exposure, though effects are in general dose related to exposure, there is evidence for individual susceptibility. As with tobacco exposure, a possible host factor is the reactivity of airways to inhaled materials.(ABSTRACT TRUNCATED AT 250 WORDS)