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At least 1,765 records · Page 98Linked to original sources
PubMed2000

Mouse submandibular gland morphogenesis: a paradigm for embryonic signal processing.

Signal processing is the sine qua non of embryogenesis. At its core, any single signal transduction pathway may be understood as classic Information Theory, adapted as an open system such that, because of networking, the "receiver" is presented with more information than was initially signaled by the "source". Over 40 years ago, Waddington presented his "Epigenetic Landscape" as a metaphor for the hierarchical nature of embryogenesis. Mathematically, Waddington's landscape may be modeled as a neural net. The "black box" of the neural net is an interacting network of signal transduction pathways (using hormones, growth factors, cytokines, neurotransmitters, and others) which inform the Boolean logic gates. An emerging theme in developmental biology is that defined sets of epigenetic circuits are used in multiple places, at multiple times, for similar and sometimes different purposes during organogenesis. As we show here, submandibular gland embryonic and fetal development is a splendid paradigm of these epigenetic circuits and their phenotypic outcomes, such as branching and lumen formation.

Animals↗
PubMed2004

PASBio: predicate-argument structures for event extraction in molecular biology.

BACKGROUND: The exploitation of information extraction (IE), a technology aiming to provide instances of structured representations from free-form text, has been rapidly growing within the molecular biology (MB) research community to keep track of the latest results reported in literature. IE systems have traditionally used shallow syntactic patterns for matching facts in sentences but such approaches appear inadequate to achieve high accuracy in MB event extraction due to complex sentence structure. A consensus in the IE community is emerging on the necessity for exploiting deeper knowledge structures such as through the relations between a verb and its arguments shown by predicate-argument structure (PAS). PAS is of interest as structures typically correspond to events of interest and their participating entities. For this to be realized within IE a key knowledge component is the definition of PAS frames. PAS frames for non-technical domains such as newswire are already being constructed in several projects such as PropBank, VerbNet, and FrameNet. Knowledge from PAS should enable more accurate applications in several areas where sentence understanding is required like machine translation and text summarization. In this article, we explore the need to adapt PAS for the MB domain and specify PAS frames to support IE, as well as outlining the major issues that require consideration in their construction. RESULTS: We introduce PASBio by extending a model based on PropBank to the MB domain. The hypothesis we explore is that PAS holds the key for understanding relationships describing the roles of genes and gene products in mediating their biological functions. We chose predicates describing gene expression, molecular interactions and signal transduction events with the aim of covering a number of research areas in MB. Analysis was performed on sentences containing a set of verbal predicates from MEDLINE and full text journals. Results confirm the necessity to analyze PAS specifically for MB domain. CONCLUSIONS: At present PASBio contains the analyzed PAS of over 30 verbs, publicly available on the Internet for use in advanced applications. In the future we aim to expand the knowledge base to cover more verbs and the nominal form of each predicate.

Cybernetics↗
PubMed2005

The influence of objectives, learning experiences and examination blueprint on medical students' examination preparation.

BACKGROUND: The influence of intended and informal curricula on examination preparation has not been extensively studied. This study aims to firstly describe how students utilized components of intended and informal curricula to guide examination preparation, and secondly to study the relationship between examination preparation and performance. METHODS: Students received a pre-examination questionnaire to identify components from the intended curriculum (objectives and examination blueprint), and informal curriculum (content emphasised during lectures and small groups), used during examination preparation. Multiple logistic regression was used to study the relationship between these variables and student performance (above versus at or below average). RESULTS: Eighty-one students participated. There was no difference in the proportions using the examination blueprint, content emphasised during lectures, and content emphasised during small groups (87-93%) but fewer students used objectives (35%, p < 0.001). Objectives use was associated with reduced odds of above average examination performance (adjusted odds ratio 0.27 [0.07, 0.97], p = 0.04). CONCLUSION: When preparing for the renal course examination, students were influenced at least as much by the informal as the intended curriculum. Of the two intended curriculum components, the examination blueprint appeared to be more widely used than the course objectives. This decreased use of objectives on examination preparation did not appear to have a detrimental effect on student performance.

Adult↗
PubMed1991

Affects as central organising and integrating factors. A new psychosocial/biological model of the psyche.

A new psychosocial/biological model of the psyche is proposed, in which the affects play a central role in organising and integrating cognition. The psyche is understood here as a complex hierarchical structure of affective/cognitive systems of reference (or 'programmes for feeling, thinking, and behaviour'), generated by repetitive concrete action. These systems store past experience in their structure, and provide the functional basis for further cognition and communication. Affects endow these programmes with a specific qualitative value (such as motivation), connect cognitive elements synchronically and diachronically, and contribute to their storage and mobilisation according to context. They also participate in differentiating cognitive systems at higher levels of abstraction. These assumptions are supported by recent findings on the role of the limbic and hypothalamic system for the regulation of emotion, on neuronal plasticity, and on the phenomenon of state-dependent learning and memory. Refutable hypotheses are formulated for further research on the interaction of emotion and cognition.

Affect↗
PubMed1999

The design of telepresence systems: the task-dependent use of binocular disparity and motion parallax.

The effect of different visual depth cues presented through a head-mounted display in a dark (no pictorial cue) environment was investigated. The relative effects of binocular disparity, motion parallax, and a combination of the 2, were assessed for 3 tasks at 2 viewing distances. These tasks (which varied in the minimum amount of information they required) were a nulling task, setting a triangle to be equilateral and matching the base-to-apex magnitude of 2 triangles at different distances. Performance within the tasks varied considerably but was most accurate for the nulling task. Differences between viewing conditions may be due to a failure in the assessment of absolute viewing distance. It is argued that these results are task specific. Although there was some variation between different cue types, they appear to be largely interchangeable within the tasks. These results have implications for system designers selecting an appropriate display device for a telepresence system.

Adult↗
PubMed1998

Aftereffects and sense of presence in virtual environments: formulation of a research and development agenda.

This report represents a committee summary of the current state of knowledge regarding aftereffects and sense of presence in virtual environments (VEs). The work presented in this article, and the proposed research agenda, are the result of a special session that was set up in the framework of the Seventh International Conference on Human Computer Interaction. Recommendations were made by the committee regarding research needs in aftereffects and sense of presence, and, where possible, priorities were suggested. The research needs were structured in terms of the short, medium, and long term and, if followed, should lead toward the effective use of VE technology. The 2 most critical research issues identified were (a) standardization and use of measurement approaches for aftereffects and (b) identification and prioritization of sensorimotor discordances that drive aftereffects. Identification of aftereffects countermeasures (i.e., techniques to assist users in readily transitioning between the real and virtual worlds), reduction of system response latencies, and improvements in tracking technology were also thought to be of critical importance.

Adaptation, Physiological↗
PubMed2005

Simulation and robotics studies of salamander locomotion: applying neurobiological principles to the control of locomotion in robots.

This article presents a project that aims at understanding the neural circuitry controlling salamander locomotion, and developing an amphibious salamander-like robot capable of replicating its bimodal locomotion, namely swimming and terrestrial walking. The controllers of the robot are central pattern generator models inspired by the salamander's locomotion control network. The goal of the project is twofold: (1) to use robots as tools for gaining a better understanding of locomotion control in vertebrates and (2) to develop new robot and control technologies for developing agile and adaptive outdoor robots. The article has four parts. We first describe the motivations behind the project. We then present neuromechanical simulation studies of locomotion control in salamanders. This is followed by a description of the current stage of the robotic developments. We conclude the article with a discussion on the usefulness of robots in neuroscience research with a special focus on locomotion control.

Animals↗
PubMedDate not supplied

An introduction to object recognition.

In this report we present a general introduction to object recognition. We begin with brief discussions of the terminology used in the object recognition literature and the psychophysical tasks that are used to investigate object recognition. We then discuss models of shape representation. We dispense with the idea that shape representations are like the 3-D models used in computer aided design and explore instead models of shape representation that are based on future descriptions. As these descriptions encode only the features that are visible from a particular viewpoint, they are generally viewpoint-specific. We discuss various means of achieving viewpoint-invariant recognition using such descriptions, including reliance on diagnostic features visible from a wide range of viewpoints, storage of multiple descriptions for each object, and the use of transformation mechanisms. Finally, we discuss how differences in viewpoint dependence that are often observed for within-category and between-category recognition tasks could be due to differences in the types of features that are naturally available to distinguish among different objects in these tasks.

Artificial Intelligence↗
PubMed2005

Attentive navigation for viewpoint control in virtual environments.

Three-dimensional virtual environments and teleoperation activities depend on the ability to position an egocentric viewpoint at meaningful locations. Evidence from foundational research has led to the development of control strategies that generally adopt an all-or-nothing approach to guiding the viewer to useful vistas. This work examines attentive navigation, a technique for partially automating viewpoint control to promote a supportive yet unscripted exploration of a virtual environment. A collection of three experiments was designed to assess the effectiveness of attentive navigation versus commonly used free navigation techniques. Results show that this approach has promising consequences for improving object recognition, developing an understanding of the configuration of objects, and searching for target objects. Actual or potential applications of this research include improved interaction techniques for extracting information from visual representations, virtual environments, and teleoperation experiences.

Adolescent↗