Showing papers by "University of Oregon published in 1986"

"Schema Abstraction" in a Multiple-Trace Memory Model

Abstract: A simulation model of episodic memory, MINERVA 2, is applied to the learning of concepts, as represented by the schema-abstraction task. The model assumes that each experience produces a separate memory trace and that knowledge of abstract concepts is derived from the pool of episodic traces at the time of retrieval. A retrieval cue contacts all traces simultaneously, activating each according to its similarity to the cue, and the information retrieved from memory reflects the summed content of all activated traces responding in parallel. The MINERVA 2 model is able to retrieve an abstracted prototype of the category when cued with the category name and to retrieve and disambiguate a category name when cued with a category exemplar. The model successfully predicts basic findings from the schema-abstraction literature (e.g., differential forgetting of prototypes and old instances, typicality, and category size effects), including some that have been cited as evidence against exemplar theories of concepts. The model is compared to other classification models, and its implications regarding the abstraction problem are discussed. How is abstract knowledge related to specific experience? In present-day terms, this question concerns the relationship between episodic and generic memories. This article explores the possibility that there is only one memory system, which stores episodic traces, and that abstract knowledge as such does not have to be stored but can be derived from the pool of traces of specific experiences at the time of retrieval. I demonstrate how this might work by applying a simulation model of a multipletrace memory theory to the sehema-abstraction experimental paradigm, which is widely believed to capture in the laboratory the processes by which generic or abstract ideas are formed. Multiple-trace theories assume that each event to which one attends gives rise to its own memory trace. Thus, repetition of an item such as a word in a list does not strengthen a prior representation (i.e., one predating the experiment or one laid down by the item's first experimental occurrence); rather, it produces a new trace that coexists in memory with traces of other occurrences of the same item. Experiments supporting the multiple-trace assumption have been primarily concerned with the ability of subjects to remember an item's presentation frequency, list membership, presentation modality, exposure duration, serial position, and so forth (e.g., Hintzman, 1976; Hintzman & Block, 1971; Hintzman, Block, & Summers, 1973;

Understanding and preventing relapse.

Abstract: This chapter examines relapse by integrating knowledge from the disorders of alcoholism, smoking, and obesity in an attempt to emphasize in a prototypical manner the overlap in etiological mechanisms and treatment rationales for disorders with powerful, underlying biological self-regulation components. Commonalities across these areas suggest at least three basic stages of behavior change: motivation and commitment, initial change, and maintenance. A distinction is made between the terms lapse and relapse, with lapse referring to the process (slips or mistakes) that may or may not lead to an outcome (relapse). The natural history of relapse is discussed, as are the consequences of relapse for patients and the professionals who treat them. Information on determinants and predictors of relapse is evaluated, with the emphasis on the interaction of individual, environmental, and physiological factors. Methods of preventing relapse are proposed and are targeted to the three stages of change. Specific research needs in these areas are discussed.

Boredom proneness--the development and correlates of a new scale.

Abstract: This article reports the development, validation, and correlates of a self-report measure of boredom proneness. The 28-item Boredom Proneness (BP) Scale demonstrates satisfactory levels of internal consistency (coefficient alpha = .79) and test-retest reliability (r = .83) over a 1-week interval. Evidence of validity for the BP is supported by correlations with other boredom measures and from a set of studies evaluating interest and attention in the classroom. Other hypothesized relationships with boredom were tested, with significant positive associations found with depression, hopelessness, perceived effort, loneliness, and amotivational orientation. Additional findings indicate boredom proneness to be negatively related to life satisfaction and autonomy orientation. The relationship of boredom to other affective states is discussed, and directions for future research are outlined.

Aging and posture control: changes in sensory organization and muscular coordination.

Abstract: The following study examined two aspects of balance control in the older adult: the coordination of the timing and the amplitude of muscle responses to postural perturbations, and the ability of the participant to reorganize sensory inputs and subsequently modify postural responses as a consequence of changing environmental conditions. Coordination of muscle activity in postural responses of twelve elderly (sixty-one to seventy-eight years) participants were compared to those of young (nineteen to thirty-eight years) adults using a movable platform and recording the electromyographic activity of muscles of the legs. The following changes were noted in the timing and amplitude of muscle activity within a postural response synergy: increases in the absolute latency of distal muscle responses were observed in all older adults; in five of the twelve older adults temporal reversals of proximal and distal muscle response onset were observed; and there was a breakdown in the correlation of the amplitude of responses within a synergy. The ability of the older adult to balance under conditions of reduced or conflicting sensory information was also impaired. When confronted with functionally inappropriate visual and/or somatosensory inputs, half of the older group lost balance. In most instances, however, the older participants were able to maintain stability during subsequent responses to conflicting stimuli.

The Geometry of Two-Weight Codes

Abstract: On etudie les relations entre les codes [n,k] lineaires a deux poids, les ensembles (n,k,h 1 h 2 ) projectifs et certains graphes fortement reguliers

Development and axonal outgrowth of identified motoneurons in the zebrafish

Abstract: We have observed the development of live, fluorescently labeled motoneurons in the spinal cord of embryonic and larval zebrafish. There are 2 classes of motoneurons: primary and secondary. On each side of each spinal segment there are 3 individually identifiable primary motoneurons, named CaP, MiP, and RoP. The motoneurons of the embryo and larva are similar in morphology and projection pattern to those of the adult. During initial development, axons of primary motoneurons make cell-specific, divergent pathway choices and grow without error to targets appropriate for their adult functions. We observed no period of cell death, and except for one consistently observed case, there was no remodeling of peripheral arbors. We have observed a consistent temporal sequence of axonal outgrowth within each spinal segment. The CaP motor axon is the first to leave the spinal cord, followed by the axons of the other primary motoneurons. The Mauthner growth cone enters the spinal cord after all the primary motoneurons of the trunk spinal cord have begun axonal outgrowth. Secondary motor growth cones appear only after the Mauthner growth cone has passed by. Our results suggest that this stereotyped temporal sequence of axonal outgrowth may play a role in defining the contacts between the Mauthner axon and the motoneurons; the behavior of growth cones in the periphery suggests that interactions with the environment, not timing, may determine path-finding and peripheral connectivity of the motoneurons.

Social support and smoking cessation and maintenance.

Abstract: Deux etudes longitudinales, prospectives, examinent le role du soutien social dans le maintien de la decision de ne plus fumer: soutien d'un partenaire; existence d'un climat social encourageant le sevrage; participation a un reseau social. Part de chacun des facteurs dans le maintien de la decision et l'absence de rechute. Etudes psychometriques

Pathway selection by growth cones of identified motoneurones in live zebra fish embryos

Abstract: How is the adult pattern of connections between motoneurones and the muscles that they innervate established during vertebrate development? Populations of motoneurones are thought to follow one of two patterns of development: (1) motor axons initially follow stereotyped pathways1 and project to appropriate regions of the developing muscle2–4 or (2) motor axons initially project to some regions that are incorrect, the inappropriate projections being eliminated subsequently5–9. Here we observed individually identified motoneurones in live zebra fish embryos as they formed growth cones and as their growth cones navigated towards their targets. We report that from axogenesis, each motor axon followed a stereotyped pathway and projected only to the specific region of the muscle appropriate for its adult function10. In addition, the peripheral arbor established by each motoneurone was restricted to a stereotyped region of its own segment and did not overlap with the peripheral arbor of the other motoneurones in that segment. We conclude that the highly stereotyped pattern of innerva-tion seen in the adult is due to initial selection of the appropriate pathway, rather than elimination of incorrect projections.

Genetic control of melatonin synthesis in the pineal gland of the mouse.

Abstract: Pineal melatonin may play an important role in regulation of vertebrate circadian rhythms and in human affective disorders. In some mammals, such as hamsters and sheep, melatonin is involved in photoperiodic time measurement and in control of reproduction. Although wild mice (Mus domesticus) and some wild-derived inbred strains of mice have melatonin in their pineal glands, several inbred strains of laboratory mice (for example, C57BL/6J) were found not to have detectable melatonin in their pineal glands. Genetic analysis suggests that melatonin deficiency in C57BL/6J mice results from mutations in two independently segregating, autosomal recessive genes. Synthesis of melatonin from serotonin in the pineal gland requires the enzymes N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT). Pineal glands from C57BL/6J mice have neither NAT nor HIOMT activity. These results suggest that the two genes involved in melatonin deficiency are responsible for the absence of normal NAT and HIOMT enzyme activity.

Climatic response surfaces from pollen data for some eastern North American taxa

Abstract: Ecological response surfaces are nonlinear functions describing the way in which the abundances of taxa depend on the joint effects of two or more environmental variables. Continental-scale patterns in the relative abundances of plant taxa are dominated by the effects of macroclimate on the competitive balance among taxa. Pollen analyses record such regional variations for major vegetation components. Empirical ecological response surfaces were derived from high-resolution climate models to yield testable reconstructions of vegeta- eastern North America. The surfaces were obtained by second- or third-degree polynomial regression on two predictor variables, mean July temperature and annual precipitation, with various nonlinear transformations of variables to allow flexibility of shape. Response surface analysis consists of a remapping of abundance patterns from geographic space into climate space, and complements efforts to explain distri- butions in terms of biological processes. Each fitted surface is unique. The surfaces focus attention on the climatic location of range limits and optima, and on less obvious phenomena such as the spatial pattern in the relative sensitivity of different taxa to spatial variation in the climatic variables. Given certain assump- tions, response surfaces based directly on pollen data may be used collectively in a global nonlinear method for estimating past climates from postglacial pollen data. Such response surfaces may also be coupled to palaeoclimatic simulations from high-resolution climate models to yield testable reconstructions of vegeta- tional history.

Segmental homologies among reticulospinal neurons in the hindbrain of the zebrafish larva.

Abstract: We have examined the morphology of identified reticulospinal neurons in larval zebrafish by retrogradely labeling them with horseradish peroxidase. We described the morphology of 27 different types of reticulospinal neurons found in the hindbrain 5 days after fertilization. Nineteen of these types are present as single identified neurons on each side of the brain; the others are present as pairs or small groups of cells. The hindbrain reticulospinal neurons are present in seven bilateral clusters that are spaced periodically along the neuraxis. Each cluster contains two to five different types of reticulospinal neurons. Cells with similar morphological features are found in adjacent clusters. By considering cell position within the cluster and axon pathway, nearly all of the cells can be assigned to one of about seven serially repeated classes. Independent morphological features of the cells support the same classification. We propose that the clusters represent hindbrain segments and that the neurons of the same class that are present in the different clusters are segmental homologues. Assuming that this series evolved by successive duplications and divergence of the primitive segments, we have analyzed the changes that may have occurred during the evolution of each new segment. Changes between ipsilaterally and contralaterally projecting axons may have occurred several times during the evolution of the series. In addition, cells may have been added or deleted.

Metabolite transfer via enzyme-enzyme complexes.

Abstract: The concentrations of enzyme sites in cells are usually higher than the concentrations of cognate intermediary metabolites. Therefore metabolic pathways or substantial segments of pathways may proceed by the direct transfer of metabolites from one enzyme site to the next by means of enzyme-enzyme complex formation. This mechanism of metabolite transfer differs from that usually assumed where dissociation and random diffusion of metabolite through the aqueous environment is responsible for the transfer to the next enzyme site. Since the direct transfer mechanism does not involve the aqueous environment, the energetics of metabolite interconversion can differ from expectations based on aqueous solution data. Evidence is summarized suggesting that metabolite is transformed and transferred with equal facility everywhere in the direct transfer pathway.

Segregation analyses and gene-centromere distances in zebrafish

Abstract: The gol-1, gol-2, alb-1 and spa-1 mutations affect pigment pattern in the zebrafish. We show here that these loci are unlinked to each other. In addition, gene-centromere distances were determined for these loci by analysis of half-tetrads obtained by the inhibition of the second meiotic division. The fractions of tetratype (second-division segregation) tetrads range from 0.24 (spa-1) to 0.89 (gol-1). The observation of greater than 0.67 second-division segregation indicates that the zebrafish has high chiasma interference.

Redefining Outdoor Education: A Matter of Many Relationships

Abstract: A new definition of outdoor education founded upon six major points is presented. Outdoor education: (1) is a method for learning; (2) is experiential; (3) takes place primarily in the outdoors; (4) requires use of all senses and domains; (5) is based upon interdisciplinary curriculum matter; and (6) is a matter of relationships involving people and natural resources. The metaphorical model of a tree describes two approaches to outdoor education. Adventure education relates to interpersonal and intrapersonal relationships. Environmental education concentrates on ecosystemic and ekistic relationships. The author maintains that both approaches, properly integrated, achieve objectives for all four relationships, and, in the process, create a truly functional outdoor education experience.

Relationship of life events and social support with psychological dysfunction among adolescents.

Abstract: Relationships among major life events, perceived social support, and psychological disorder were assessed in a sample of older adolescents. Negative life events and satisfaction with social support were significantly and independently related to a range of psychological symptoms. Further, the relationship between negative events and disorder was moderated by gender, the types of events experienced, and anticipated change in the psychosocial environment. The importance of the use of standardized and psychometrically sound measures of life events, social support, and psychological disorder is highlighted.

Carbon-isotope events across the Precambrian/Cambrian boundary on the Siberian Platform

Abstract: Variations of marine isotopes with time have been observed through the Phanerozoic1,2, in association with some period boundaries: Pleistocene/Holocene3, Cretaceous/Tertiary4, Permo-Triassic5,6 and Frasnian/Fammenian7 Most of these changes are associated with extinction events, reflecting changes in life on Earth One of the major biological changes in Earth's history occurred near the end of Proterozoic time, with widespread increase of bio-mineralization and the appearance of shelly fauna8–10 We present here an initial survey of carbon isotope ratios in a section on the Siberian Platform that spans the Proterozoic/Palaeozoic boundary After a high of δ13C = + 34‰, 15 m below the boundary, δ13C drops sharply in two cycles across the boundary, to δ13C = −2‰, near the end of the Tommotian Stage These variations suggest an initial bloom of biomass in late Vendian time corresponding to the dramatic diversification that must have preceeded the widespread appearance of new taxa in the Cambrian fossil record

The Nine Nations of North America and the Value Basis of Geographic Segmentation

Abstract: The utility of the concept of the “Nine Nations of North America” for segmentation was tested by comparing several geographic segmentation systems with values in a probability sample of the cotermi...

Kinetics of protein-nucleic acid interactions: use of salt effects to probe mechanisms of interaction.

Abstract: The kinetics of protein-nucleic acid interactions are discussed with particular emphasis on the effects of salt concentration and valence on the observed rate constants. A general review is given of the use of experimentally determined salt dependences of observed kinetic parameters as a tool to probe the mechanism of interaction. Quantitative analysis of these salt dependences, through the application of polyelectrolyte theory, can be used to distinguish reactions which occur in a single step from those reactions which involve distinct intermediates. For those rate constants which display a large salt dependence, in either the association or dissociation reaction, this is due to the high concentration of counterions (e.g., Na+) in the vicinity of the nucleic acid which are subsequently released (or bound in the case of dissociation) at some point before the rate limiting step of the reaction. A general discussion of other features which affect protein-nucleic acid kinetics, such as nucleic acid length and the ratio of nonspecific to specific DNA binding sites (in the case of sequence specific binding proteins), is also given. The available data on the nucleic acid binding kinetics of small ligands (ions, dyes, oligopeptides), nonspecific binding proteins (T4 gene 32 protein, fd gene 5 and Escherichia coli SSB), and sequence specific binding proteins (lac repressor, RNA polymerase, Eco RI restriction endonuclease) are discussed with emphasis on the interpretation of the experimentally determined salt dependences.

Cooperative and noncooperative binding of protein ligands to nucleic acid lattices: experimental approaches to the determination of thermodynamic parameters.

Abstract: Many biologically important proteins bind nonspecifically, and often cooperatively, to single-or double-stranded nucleic acid lattices in discharging their physiological functions. This binding can generally be described in thermodynamic terms by three parameters: n, the binding site size; K, the intrinsic binding constant; omega, the binding cooperativity parameter. The experimental determination of these parameters often appears to be straightforward but can be fraught with conceptual and methodological difficulties that may not be readily apparent. In this paper we describe and analyze a number of approaches that can be used to measure these protein-nucleic acid interaction parameters and illustrate these methods with experiments on the binding of T4-coded gene 32 (single-stranded DNA binding) protein to various nucleic acid lattices. We consider the following procedures: (i) the titration of a fixed amount of lattice (nucleic acid) with added ligand (protein); (ii) the titration of a fixed amount of ligand with added lattice; (iii) the determination of ligand binding affinities at very low levels of lattice saturation; (iv) the analysis of ligand cluster size distribution on the lattice; (v) the analysis of ligand binding to lattices of finite length. The applicability and limitations of each approach are considered and discussed, and potential pitfalls are explicitly pointed out.

Tissue-specific cell lineages originate in the gastrula of the zebrafish.

Abstract: In the zebrafish, cells of a clone derived from a single blastomere migrate away from one another during gastrulation. Later in development their descendants are usually found scattered within several different types of tissues of embryo. The divisions and migrations of individual cells were monitored during early development, revealing that in most cases the lineal descendants of single cells present at gastrula stage exclusively populate only single tissues, and may have stereotyped positional relationships within these tissues. Thus the gastrula stage is the first stage when heritable restrictions in cell type might arise in the zebrafish.

Dropping in and dropping out: participation motives of current and former youth gymnasts.

Abstract: This study examined motives for participating in and discontinuing sport for 106 competitive, recreational, and former youth gymnasts. Similar to previous studies on participation motives in children's sport, gymnasts cited multiple reasons for their attraction to sport with the most important being competence, fitness, and challenge for the competitive gymnasts; competence, fitness, fun and situational for the recreational gymnasts; and competence, action, challenge and fun for the former gymnasts. A factor analysis was conducted and revealed seven categories of motivational factors, similar to those found by Gill et al. (1983). No support was found for a relationship between motives for gymnastic participation and reasons for attrition. The most important reasons for leaving gymnastics were having other things to do, injuries, not liking the pressure, not having enough fun, and too time consuming.

Enzyme–Enzyme Interactions and the Regulation of Metabolic Reaction Pathways

Abstract: Publisher Summary This chapter focuses on enzyme-enzyme interactions and the regulation of metabolic reaction pathways. The existence of functional enzyme-enzyme interactions is most obvious in the case of multienzyme systems. The term “multienzyme system” is used to describe a variety of catalytically functional proteins, all of which have the property of association of more than one kind of functionally active enzyme within a specifically aggregated molecule. In general, evidence relevant to the function of enzyme-enzyme interactions comes from two sources: (1) the specific details of quaternary structural interactions between or among the enzyme subunits, and (2) kinetic studies, primarily involving the effectiveness of competition of a metabolic intermediate with the precursor metabolite for the formation of the final product. The individual protein concentrations in multienzyme systems are enormously high. For example, the individual enzyme site concentrations within the pyruvate dehydrogenase complex are approximately 10 mM. Many enzyme-enzyme interactions have been noted among soluble mitochondrial enzymes in in vitro experiments.