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Clear Predictions (clear + prediction)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Neuronal plasticity: implications in epilepsy progression and management

DRUG DEVELOPMENT RESEARCH, Issue 8 2007
Sherifa A. HamedArticle first published online: 12 FEB 200
Abstract Epilepsy is a common neurological disease. A growing number of research studies provide evidence regarding the progressive neuronal damage induced by prolonged seizures or status epilepticus (SE), as well as recurrent brief seizures. Importantly, seizure is only one aspect of epilepsy. However, cognitive and behavioral deficits induced by progressive seizures or antiepileptic treatment can be detrimental to individual function. The neurobiology of epilepsy is poorly understood involving complex cellular and molecular mechanisms. The brain undergoes changes in its basic structure and function, e.g., neural plasticity with an increased susceptibility in neuronal synchronization and network circuit alterations. Some of these changes are transient, while others are permanent with an involvement of both glutamatergic and ,-aminobutyric acid (GABA)ergic systems. Recent data suggest that impaired neuronal plasticity may underlie the cognitive impairment and behavioral changes associated with epilepsy. Many neurologists recognize that the prevention or suppression of seizures by the use of antiepileptic drugs (AEDs) alone is insufficient without clear predictions of disease outcome. Hence, it is important to understand the molecular mechanisms underlying epileptogenesis because this may allow the development of innovative strategies to prevent or cure this condition. In addition, this realization would have significant impact in reducing the long-term adverse consequences of the disease, including neurocognitive and behavioral adverse effects. Drug Dev Res 68:498,511, 2007. © 2008 Wiley-Liss, Inc. [source]

A neuroanatomically grounded Hebbian-learning model of attention,language interactions in the human brain

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2008
Max Garagnani
Abstract Meaningful familiar stimuli and senseless unknown materials lead to different patterns of brain activation. A late major neurophysiological response indexing ,sense' is the negative component of event-related potential peaking at around 400 ms (N400), an event-related potential that emerges in attention-demanding tasks and is larger for senseless materials (e.g. meaningless pseudowords) than for matched meaningful stimuli (words). However, the mismatch negativity (latency 100,250 ms), an early automatic brain response elicited under distraction, is larger to words than to pseudowords, thus exhibiting the opposite pattern to that seen for the N400. So far, no theoretical account has been able to reconcile and explain these findings by means of a single, mechanistic neural model. We implemented a neuroanatomically grounded neural network model of the left perisylvian language cortex and simulated: (i) brain processes of early language acquisition and (ii) cortical responses to familiar word and senseless pseudoword stimuli. We found that variation of the area-specific inhibition (the model correlate of attention) modulated the simulated brain response to words and pseudowords, producing either an N400- or a mismatch negativity-like response depending on the amount of inhibition (i.e. available attentional resources). Our model: (i) provides a unifying explanatory account, at cortical level, of experimental observations that, so far, had not been given a coherent interpretation within a single framework; (ii) demonstrates the viability of purely Hebbian, associative learning in a multilayered neural network architecture; and (iii) makes clear predictions on the effects of attention on latency and magnitude of event-related potentials to lexical items. Such predictions have been confirmed by recent experimental evidence. [source]

EXPERIMENTAL MANIPULATION OF SEXUAL SELECTION PROMOTES GREATER MALE MATING CAPACITY BUT DOES NOT ALTER SPERM INVESTMENT

EVOLUTION, Issue 4 2009
Helen S. Crudgington
Sexual selection theory makes clear predictions regarding male spermatogenic investment. To test these predictions we used experimental sexual selection in Drosophila pseudoobscura, a sperm heteromorphic species in which males produce both fertile and sterile sperm, the latter of which may function in postmating competition. Specifically, we determined whether the number and size of both sperm types, as well as relative testis mass and accessory gland size, increased with increased sperm competition risk and whether any fitness benefits could accrue from such changes. We found no effect of sexual selection history on either the number or size of either sperm morph, or on relative testis mass. However, males experiencing a greater opportunity for sexual selection evolved the largest accessory glands, had the greatest mating capacity, and sired the most progeny. These findings suggest that sterile sperm are not direct targets of sexual selection and that accessory gland size, rather than testis mass, appears to be an important determinant of male reproductive success. We briefly review the data from experimental sexual selection studies and find that testis mass may not be a frequent target of postcopulatory sexual selection and, even when it is, the resulting changes do not always improve fitness. [source]

Dynamics of regional coexistence for more or less equal competitors

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2003
C. Patrick Doncaster
Summary 1Competition between two species in a metapopulation involves each inhibiting the other's ability firstly to colonize an already occupied area and then to persist in it. Models for regional competition of this kind have 3-D dynamics, from which it has proved difficult to extract useful predictions except for special conditions. We introduce a 2-D general model for species that are equally vigorous at inhibiting the ability of others to remain in an occupied patch as to arrive there. The model covers the full spectrum of competitive interactions, from weak to strong and symmetrical to asymmetrical. Its Lotka,Volterra dynamics extend the general theory of competitive coexistence by generating clear predictions for community structure, amenable to cross-system comparisons and experimental manipulations. 2Previous 2-D models of interactions between dominant and fugitive species are special cases of the 2-D general model. Moderately asymmetrical competition has two outcomes distinctly different from dominant,fugitive interactions, at both the scale of metapopulation and population: (i) slow growing and weak competitors coexist with faster growing superior competitors, albeit at reduced densities; and (b) habitat removal always yields relative gains in abundance for species with higher growth capacity, but the gains are absolute only for species subjected to competitive impacts that exceed within-species impacts. Extinctions of slow growing and weak competitors provide the most sensitive indication of habitat degradation, and their losses also have the least effect on community structure. 3The 2-D general model further predicts that highly productive communities will tolerate differences between species in their capacity for population growth, whereas less productive communities will tolerate stronger competitive interactions between species. This prediction applies equally to a population of resource consumers as to a metapopulation of colonists. The model explicitly links local and regional population dynamics to r,K selection in community structure by predicting a prevalence of growth-orientated species in resource-poor habitats and competition-orientated species in resource-rich habitats. [source]

Why Are You Learning a Second Language?

LANGUAGE LEARNING, Issue S1 2003
Motivational Orientations, Self-Determination Theory
The data for this study were collected in my first year of graduate school for a term paper for a course I was taking from Luc Pelletier. When I began graduate school, Luc also started at the University of Ottawa as a new faculty member, and he taught a course in motivation. I had worked with Richard Clément for a couple of years already as an honors student and as a research assistant and had conducted research on orientations and motivation under his supervision as part of my honors thesis project. Luc was very interested in self-determination theory (SDT) and had worked with Bob Vallerand on an instrument to assess academic motivation from this perspective. Luc and I decided to carry out a study on language learning orientations using SDT and enlisted Richard's and Bob's involvement in the project. As a bilingual institution where all students were required to demonstrate competence in their second language (L2), whether French or English, the University of Ottawa was an ideal setting for this type of research. The project was a first examination of SDT in the language learning context, and to the best of my knowledge it was the only, or at least one of the very few, empirical investigations of intrinsic and extrinsic motivation in the area. It involved the development of a valid and reliable instrument to assess the different subtypes of intrinsic and extrinsic motivation. It also explored the link between these motivational subtypes and various orientations to language learning that had been identified by Clément and Kruidenier (1983), including the travel, friendship, knowledge, and instrumental orientations. The results showed that the instrumental orientation and the SDT external regulation orientation were strongly correlated, and that the travel, friendship, and knowledge orientations were quite highly intercorrelated with identified regulation and intrinsic motivation. Moreover, the instrumental and external regulation orientation scales correlated in similar ways with the hypothesized antecedents of perceived autonomy and competence and the hypothesized consequences of intention to pursue L2 study and anxiety. In addition, the travel, friendship, and knowledge orientations were correlated with the hypothesized antecedents and consequences in a manner similar to intrinsic motivation and identified regulation. These results suggested that Clément and Kruidenier's 4 orientations may be tapping a similar construct as the SDT orientations. My only regret with this study is that I did not include a scale to measure the integrative orientation (Gardner, 1985) to determine its relation with the SDT subtypes. This issue would have to wait until a later study to be addressed. The results of this initial investigation encouraged me to pursue research integrating SDT with other theoretical frameworks of language learning motivation. I believe that the SDT framework has several advantages over some other formulations of learner orientations. SDT offers a parsimonious, internally consistent framework for systematically describing many different orientations in a comprehensive manner. It also offers considerable explanatory power for understanding why certain orientations are better predictors of relevant language learning variables (e.g., effort, persistence, attitudes) than others. Also, by invoking the psychological mechanisms of perceived autonomy, competence, and relatedness, it can account for why certain orientations are evident in some learners and not in others. Moreover, the framework is empirically testable and indeed has stood up well under empirical scrutiny in our studies. Its clear predictions may also be particularly valuable in applying the theory in language teaching and program development. [The present article first appeared in Language Learning, 50 (1), 2000, 57,85] [source]