Modeling the perceptual component of conceptual learning—A coordination perspective

Although a picture may be worth a thousand words, modeling diagrams as propositions and modeling visual processing as search through a database of verbal descriptions obscures what is problematic for the learner. Cognitive modeling of language learning and geometry has obscured the learner's problem of knowing where to look—what spaces, markings, and orientations constitute the objects of interest? Today we are launching into widespread use of multimedia instructional technology, without an adequate theory to relate perceptual processes to conceptual learning. Does this matter? In this article, I review the symbolic approach to modeling perceptual processing and show its limitations for explaining difficulties children encounter in interpreting a graphic display. I present an alternative analysis by which perceptual categorization is coupled to behavior sequences, where gesturing and emotional changes are essential for resolving impasses and breaking out of loops. I conclude by asking what kind of cognitive theory we need to exploit communication technology. Have we been correct to assume that pedagogy must be grounded in an accurate psychological model of knowledge, memory, and learning

Understanding Epileptiform After-Discharges as Rhythmic Oscillatory Transients

Electro-cortical activity in patients with epilepsy may show abnormal rhythmic transients in response to stimulation. Even when using the same stimulation parameters in the same patient, wide variability in the duration of transient response has been reported. These transients have long been considered important for the mapping of the excitability levels in the epileptic brain but their dynamic mechanism is still not well understood. To understand the occurrence of abnormal transients dynamically, we use a thalamo-cortical neural population model of epileptic spike-wave activity and study the interaction between slow and fast subsystems. In a reduced version of the thalamo-cortical model, slow wave oscillations arise from a fold of cycles (FoC) bifurcation. This marks the onset of a region of bistability between a high amplitude oscillatory rhythm and the background state. In vicinity of the bistability in parameter space, the model has excitable dynamics, showing prolonged rhythmic transients in response to suprathreshold pulse stimulation. We analyse the state space geometry of the bistable and excitable states, and find that the rhythmic transient arises when the impending FoC bifurcation deforms the state space and creates an area of locally reduced attraction to the fixed point. This area essentially allows trajectories to dwell there before escaping to the stable steady state, thus creating rhythmic transients. In the full thalamo-cortical model, we find a similar FoC bifurcation structure. Based on the analysis, we propose an explanation of why stimulation induced epileptiform activity may vary between trials, and predict how the variability could be related to ongoing oscillatory background activity.Comment: http://journal.frontiersin.org/article/10.3389/fncom.2017.00025/ful

Solving Bongard Problems with a Visual Language and Pragmatic Reasoning

More than 50 years ago Bongard introduced 100 visual concept learning problems as a testbed for intelligent vision systems. These problems are now known as Bongard problems. Although they are well known in the cognitive science and AI communities only moderate progress has been made towards building systems that can solve a substantial subset of them. In the system presented here, visual features are extracted through image processing and then translated into a symbolic visual vocabulary. We introduce a formal language that allows representing complex visual concepts based on this vocabulary. Using this language and Bayesian inference, complex visual concepts can be induced from the examples that are provided in each Bongard problem. Contrary to other concept learning problems the examples from which concepts are induced are not random in Bongard problems, instead they are carefully chosen to communicate the concept, hence requiring pragmatic reasoning. Taking pragmatic reasoning into account we find good agreement between the concepts with high posterior probability and the solutions formulated by Bongard himself. While this approach is far from solving all Bongard problems, it solves the biggest fraction yet

Characterization of peroxidase and catalase genes in defense mechanisms of Physcomitrella patens

Systemic acquired resistance (SAR) and the hypersensitive response (HR) are two important induced defense mechanisms in plants. SAR is the development of an enhanced resistance to a pathogen due to a prior encounter. It results in faster and more effective defensive action within the plant upon a second-time pathogen attack. HR is a plant defense mechanism that utilizes reactive oxygen species (ROS) to attack pathogens at the site of an infection. ROS can be generated in many ways; however, it is specifically known that plants use the enzyme peroxidase to generate the ROS hydrogen peroxide during HR. Plants also use the enzyme catalase to generate water from hydrogen peroxide in order to contain and control the toxicity. Much is known about SAR and HR in economically important vascular plants such as rice and corn; however, they have only recently been identified in nonvascular plants such as moss. This study aims to identify and characterize the roles of peroxidase and catalase in HR and SAR in the model moss species Physcomitrella patens; specifically, how the expression of peroxidase and catalase genes in this species is affected by exposure to the fungal elicitor β-glucan. This will provide insight into the SAR and HR of moss and other nonvascular plants and into the evolution of plant defense mechanisms

Human Primordial Germ Cells Are Specified from Lineage-Primed Progenitors.

In vitro gametogenesis is the process of making germline cells from human pluripotent stem cells. The foundation of this model is the quality of the first progenitors called primordial germ cells (PGCs), which in vivo are specified during the peri-implantation window of human development. Here, we show that human PGC (hPGC) specification begins at day 12 post-fertilization. Using single-cell RNA sequencing of hPGC-like cells (hPGCLCs) differentiated from pluripotent stem cells, we discovered that hPGCLC specification involves resetting pluripotency toward a transitional state with shared characteristics between naive and primed pluripotency, followed by differentiation into lineage-primed TFAP2A+ progenitors. Applying the germline trajectory to TFAP2C mutants reveals that TFAP2C functions in the TFAP2A+ progenitors upstream of PRDM1 to regulate the expression of SOX17. This serves to protect hPGCLCs from crossing the Weismann's barrier to adopt somatic cell fates and, therefore, is an essential mechanism for successfully initiating in vitro gametogenesis

Do you believe the climate Is changing? answers from new survey research

This brief explores how political views influence Americans’ understanding and perception of science. The research is based on a national version of the Community and Environment in Rural America survey called NCERA, and on New Hampshire’s statewide Granite State Poll. Author Lawrence Hamilton reports that most people on both surveys feel that they understand either a great deal or a moderate amount about global warming or climate change. However, deep partisan divisions affect both personal beliefs about climate change and perceptions of agreement among scientists. Democrats are much more likely to state they believe that climate change is happening, caused mainly by human activities. Republicans are much more likely to say they believe either that climate change is not happening, or that it is, but for natural reasons

Drawing the line: drawing and construction strategies for simple and complex figures in Williams Syndrome and typical development

In the typical population, a series of drawing strategies have been outlined, which progressively emerge during childhood. Individuals with Williams syndrome (WS), a rare genetic disorder, produce drawings that lack cohesion, yet drawing strategies in this group have hitherto not been investigated. In this study, WS and typically developing (TD) groups drew and constructed (from pre-drawn lines and shapes) a series of intersecting and embedded figures. Participants with WS made use of the same strategies as the TD group for simple intersecting figures, though were less likely to use a typical strategy for more complex figures that contained many spatial relations. When replicating embedded shapes, the WS group used typical drawing strategies less frequently than the TD group, despite attempting to initiate a strategy that is observed in TD children. Results suggested that individuals with WS show a particular difficulty with replicating figures that include multiple spatial relations. The impact of figure complexity and task demands on performance are discussed