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At least 1,423 records · Page 79Linked to original sources
PubMed2003

Visual presentation of single letters activates a premotor area involved in writing.

In the present fMRI study, we addressed the question as to whether motor-perceptual interactions might be involved in reading. Recognizing the letters encountered when reading is generally assumed to be a purely visual process, yet because we know how to write, we also possess a sensorimotor representation of the letters. Does simply viewing a letter suffice to activate the corresponding motor representation? To answer this question, we asked right-handed subjects first to look at and then to copy single letters or pseudoletters. We established that the visual presentation of letters activated a part of the left premotor cortex (BA6) that was also activated when the letters were being written by the subjects. This premotor zone resembles Exner's area, which is thought to contain the motor programs necessary for producing letters. Visually presented pseudoletters, which had never been written before by the subjects, did not activate this region. These results indicate that the writing motor processes are implicitly evoked when passively observing letters. The cerebral representation of letters is therefore presumably not strictly visual, but based on a multicomponent neural network built up while learning concomitantly to read and write. One of the components might be a sensorimotor one associated with handwriting. This finding shows the existence of close functional relations between the reading and writing processes, and suggests that our reading abilities might be somehow dependent on the way we write.

Adult↗
PubMed2003

Behavioural studies of strategic thinking in games.

Game theory is a mathematical language for describing strategic interactions, in which each player's choice affects the payoff of other players (where players can be genes, people, companies, nation-states, etc.). The impact of game theory in psychology has been limited by the lack of cognitive mechanisms underlying game-theoretic predictions. 'Behavioural game theory' is a recent approach linking game theory to cognitive science by adding cognitive details about 'social utility functions', theories of limits on iterated thinking, and statistical theories of how players learn and influence others. New directions include the effects of game descriptions on choice ('framing'), strategic heuristics, and mental representation. These ideas will help root game theory more deeply in cognitive science and extend the scope of both enterprises.

Journal Article↗
PubMed1988

Contextually relevant aspects of meaning.

A series of six experiments investigated whether inferences about contextually relevant aspects of meaning were encoded into memory during reading. In all the experiments, subjects studied short paragraphs. Then, test sentences were presented that expressed relevant aspects of meaning that had not been explicitly stated in the paragraphs. For example, for a paragraph about searching for the correct color to paint a picture of a tomato, a relevant aspect of meaning would be that tomatoes are red. The test sentences were presented either immediately following the relevant paragraph or after a delay. With immediate testing, it was argued that the facilitation obtained in verification latency could result from processes occurring either when the context was read or when the test sentence was verified. With delayed testing, evidence was found to support the hypothesis that contextually relevant aspects of meaning are incorporated into the memory representation of the paragraph, but such evidence was obtained only when the retrieval environment encouraged the use of newly learned information in the decision process on the test sentence.

Cognition↗
PubMed2005

Auditory feedback in music performance: the role of melodic structure and musical skill.

Five experiments explored whether fluency in musical sequence production relies on matches between the contents of auditory feedback and the planned outcomes of actions. Participants performed short melodies from memory on a keyboard while musical pitches that sounded in synchrony with each keypress (feedback contents) were altered. Results indicated that altering pitch contents can disrupt production, but only when altered pitches form a sequence that is structurally similar to the planned sequence. These experiments also addressed the role of musical skill: Experiments 1 and 3 included trained pianists; other experiments included participants with little or no musical training. Results were similar across both groups with respect to the disruptive effects of auditory feedback manipulations. These results support the idea that a common hierarchical representation guides sequences of actions and the perception of event sequences and that this coordination is not acquired from learned associations formed by musical skill acquisition.

Adolescent↗
PubMed1991

The value and future agenda of research on teaching physical education.

Research on teaching physical education is important because teaching is central to the school institution. Consistent results have emerged from research on teaching. A moral imperative exists for continued efforts to refine what we know about effective instruction in the gym. In spite of the complex, nondeterministic, and normative nature of teaching, teachers are influenced by research on teaching as they strive to improve their craft. Research on teaching physical education must move in the direction of understanding the representations teachers employ in helping students who are having difficulty mastering subject matter. Studying teachers' methods for helping students learn while mediating students' social and emotional anxieties in a range of physical education contexts will reveal the kind of knowledge that will have practical importance. We will then be able to describe practice that is successful from the perspective of students and those who set standards for education's results.

Behavior↗
PubMed2005

Using ergodic theory to assess the performance of ecosystem models.

Ecosystem simulation models are designed to assess the flux of energy, water, carbon and nitrogen according to a given vegetation type. The reliability of the modeled results is determined by model validations. Model validations are typically done using classical statistical methods like regression analysis of predicted versus observed values, paired t statistics and error assessment procedures to characterize the quality of current and future model predictions. All these validation efforts concentrate on static aspects of the model but fail to describe the model dynamics. In this paper, we introduce methods from ergodic theory to analyze the dynamic behavior of ecosystem models. We describe (1) how the attractor representation of model behavior can be reconstructed from a time series of model outputs, and (2) what we can learn from the attractor to assess the model dynamics. As an application example, we provide simulation results for two important pine forest ecosystems in Austria, i.e., 23 Cembran pine and 16 Scots pine stands. These stands were simulated with three model parameterizations: one representing a generic, evergreen needle-leaf forest, and two species- specific parameter sets, one for Cembran pine and one for Scots pine. First, we applied standard validation methods to get static measures of model accuracy and precision. Next, we used ergodic theory to assess model dynamics. A comparison of both analyses reveals important issues related to model dynamics, such as the finding that the occurrence of instabilities in model behavior may not be detected by standard validation methods. Using ergodic theory, we were able to reconstruct the attractors of model behavior. In the attractor describing model dynamics for Cembran pine, simulated with the generic, evergreen needle-leaf forest parameter set, we detected instability in model behavior. We identified this instability as a riddled basin configuration, which is a strong indicator for the occurrence of a chaotic model behavior that may result in random predictions. Our results suggest that ergodic theory is a useful tool for assessing inconsistencies in the dynamics of ecosystem model simulations that have not been detected by standard statistical validation methods.

Climate↗
PubMed1996

The somatic marker hypothesis and the possible functions of the prefrontal cortex.

In this article I discuss a hypothesis, known as the somatic marker hypothesis, which I believe is relevant to the understanding of processes of human reasoning and decision making. The ventromedial sector of the prefrontal cortices is critical to the operations postulated here, but the hypothesis does not necessarily apply to prefrontal cortex as a whole and should not be seen as an attempt to unify frontal lobe functions under a single mechanism. The key idea in the hypothesis is that 'marker' signals influence the processes of response to stimuli, at multiple levels of operation, some of which occur overtly (consciously, 'in mind') and some of which occur covertly (non-consciously, in a non-minded manner). The marker signals arise in bioregulatory processes, including those which express themselves in emotions and feelings, but are not necessarily confined to those alone. This is the reason why the markers are termed somatic: they relate to body-state structure and regulation even when they do not arise in the body proper but rather in the brain's representation of the body. Examples of the covert action of 'marker' signals are the undeliberated inhibition of a response learned previously; the introduction of a bias in the selection of an aversive or appetitive mode of behaviour, or in the otherwise deliberate evaluation of varied option-outcome scenarios. Examples of overt action include the conscious 'qualifying' of certain option-outcome scenarios as dangerous or advantageous. The hypothesis rejects attempts to limit human reasoning and decision making to mechanisms relying, in an exclusive and unrelated manner, on either conditioning alone or cognition alone.

Choice Behavior↗
PubMed2005

Practitioner review: approaches to assessment and treatment of children with DCD: an evaluative review.

BACKGROUND: Movement clumsiness (or Developmental Coordination Disorder--DCD) has gained increasing recognition as a significant condition of childhood. However, some uncertainty still exists about diagnosis. Accordingly, approaches to assessment and treatment are varied, each drawing on distinct theoretical assumptions about the aetiology of the condition and its developmental course. METHOD: This review evaluates the current status of different approaches to motor assessment and treatment for children with DCD. These approaches are divided according to their broad conceptual origin (or explanatory framework): Normative Functional Skill Approach, General Abilities Approach, Neurodevelopmental Theory, Dynamical Systems Theory, and the Cognitive Neuroscientific Approach. CONCLUSIONS: Each conceptual framework is shown to support assessment and treatment methods with varying degrees of conceptual and psychometric integrity. The normative functional skill approach supports the major screening devices for DCD and cognitive (or top-down) approaches to intervention. The general abilities approach and traditional neurodevelopmental theory are not well supported by recent research. The dynamical systems approach supports promising trends in biomechanical or kinematic analysis of movement, ecological task analysis, and task-specific intervention. Finally, and more recently, the cognitive neuroscientific approach has generated some examples of process-oriented assessment and treatment based on validated (brain-behaviour) models of motor control and learning. A multi-level approach to movement assessment and treatment is recommended for DCD, providing a more complete representation of motor development at different levels of function--behavioural, neurocognitive, and emotional.

Child↗
PubMed2000

Plasticity and primary motor cortex.

One fundamental function of primary motor cortex (MI) is to control voluntary movements. Recent evidence suggests that this role emerges from distributed networks rather than discrete representations and that in adult mammals these networks are capable of modification. Neuronal recordings and activation patterns revealed with neuroimaging methods have shown considerable plasticity of MI representations and cell properties following pathological or traumatic changes and in relation to everyday experience, including motor-skill learning and cognitive motor actions. The intrinsic horizontal neuronal connections in MI are a strong candidate substrate for map reorganization: They interconnect large regions of MI, they show activity-dependent plasticity, and they modify in association with skill learning. These findings suggest that MI cortex is not simply a static motor control structure. It also contains a dynamic substrate that participates in motor learning and possibly in cognitive events as well.

Animals↗
PubMed2001

The fiction of bioethics: a precis.

Recently, bioethics has become interested in engaging with narrative, but in this engagement, narrative is usually viewed as a mere helpmate to philosophy. In this precis to his book The Fiction of Bioethics, Tod Chambers argues that narrative theory should not be simply a helpful addition to medical ethics but instead should be thought of as being as vital and important to the discipline as moral theory itself. The reason we need to rethink the relationship of medical ethics to narrative is that ethicists test their ideas by applying them to cases, and cases are a narrative genre. Recognizing the importance that cases have for the way medical ethicists do ethics is essential in order to appreciate the field as a form of applied philosophy. Like other forms of representation, narrative has distinct and defining features, which ethicists, in order to understand the data of their field, must learn to recognize and differentiate. Ethicists need to attend to the way decisions about the discourse of a narrative influences the kind of moral theories judged relevant to it. The author briefly examines six features of narrative discourse that rhetorically condition the way we understand medical ethics cases: filter, reportability, closure, characters, chronotope, and gender.

Bioethics↗
PubMed2000

Data quality in predictive toxicology: identification of chemical structures and calculation of chemical properties.

Every technique for toxicity prediction and for the detection of structure-activity relationships relies on the accurate estimation and representation of chemical and toxicologic properties. In this paper we discuss the potential sources of errors associated with the identification of compounds, the representation of their structures, and the calculation of chemical descriptors. It is based on a case study where machine learning techniques were applied to data from noncongeneric compounds and a complex toxicologic end point (carcinogenicity). We propose methods applicable to the routine quality control of large chemical datasets, but our main intention is to raise awareness about this topic and to open a discussion about quality assurance in predictive toxicology. The accuracy and reproducibility of toxicity data will be reported in another paper.

Data Interpretation, Statistical↗
PubMed2002

Rule-based extrapolation in perceptual categorization.

Erickson and Kruschke (1998) provided a demonstration that in certain situations people will classify novel stimuli according to an extrapolated rule, even when the most similar training exemplar is an exception to the rule. This result challenged exemplar models. Nosofsky and Johansen (2000) have called this finding into question by offering an exemplar-based explanation for those data based on the perceptual features of the stimuli. Here, we describe the results of a new experiment that yields results similar to those found previously without the questionable perceptual features: Participants who learn to classify all the training stimuli have patterns of generalization that indicate a combination of rule and exemplar representation. ATRIUM, a hybrid rule and exemplar model (Erickson & Kruschke, 1998), is shown to account for these data much better than ALCOVE, an exemplar model (Kruschke, 1992). Moreover, four alternate exemplar explanations, including one suggested by Nosofsky and Johansen, cannot account for our new findings.

Cognition↗
PubMed1991

Intracerebral distribution of DL-2-amino-phosphonopentanoic acid (AP5) and the dissociation of different types of learning.

Chronic intraventricular infusion of the selective NMDA receptor antagonist AP5 appears to cause an impairment of spatial but not visual discrimination learning. However, Goddard (1986) has questioned whether this dissociation in task-selectivity reflects a difference in the underlying neural mechanisms or differential drug diffusion. Two experiments conducted to address this issue established (a) that chronic intraventricular infusion of AP5, at a dose sufficient to cause a spatial learning impairment, results in a relatively uniform distribution of the drug across the brain, and (b) that chronic bilateral intracortical infusion at sites very close to visual cortex also fails to impair visual discrimination learning. These findings argue against differential diffusion being a major cause of the sensitivity of spatial but not visual discrimination tasks to AP5, and raises the possibility that representational and procedural memory tasks may depend upon distinct cell-biological mechanisms of plasticity.

2-Amino-5-phosphonovalerate↗
PubMed2001

Generalization in interactive networks: the benefits of inhibitory competition and Hebbian learning.

Computational models in cognitive neuroscience should ideally use biological properties and powerful computational principles to produce behavior consistent with psychological findings. Error-driven backpropagation is computationally powerful and has proven useful for modeling a range of psychological data but is not biologically plausible. Several approaches to implementing backpropagation in a biologically plausible fashion converge on the idea of using bidirectional activation propagation in interactive networks to convey error signals. This article demonstrates two main points about these error-driven interactive networks: (1) they generalize poorly due to attractor dynamics that interfere with the network's ability to produce novel combinatorial representations systematically in response to novel inputs, and (2) this generalization problem can be remedied by adding two widely used mechanistic principles, inhibitory competition and Hebbian learning, that can be independently motivated for a variety of biological, psychological, and computational reasons. Simulations using the Leabra algorithm, which combines the generalized recirculation (GeneRec), biologically plausible, error-driven learning algorithm with inhibitory competition and Hebbian learning, show that these mechanisms can result in good generalization in interactive networks. These results support the general conclusion that cognitive neuroscience models that incorporate the core mechanistic principles of interactivity, inhibitory competition, and error-driven and Hebbian learning satisfy a wider range of biological, psychological, and computational constraints than models employing a subset of these principles.

Algorithms↗
PubMed2006

How we interact with objects: learning from brain lesions.

Motor deficits are the most common outcome of brain damage. Although a large part of such disturbances arises from loss of elementary sensorimotor functions, several syndromes cannot be explained purely on these bases. In this article, we briefly describe higher-order motor impairments, with specific attention to the characteristic ability of the human hand to interact with objects and tools. Disruption of this motor skill at several independent levels is used to outline a comprehensive model, in which various current proposals for a modular organization of hand-object interactions can be integrated. In this model, cortical mechanisms related to object interaction are independent from representations of the semantic features of objects.

Brain Injuries↗
PubMed1969

A theory of cerebellar cortex.

1. A detailed theory of cerebellar cortex is proposed whose consequence is that the cerebellum learns to perform motor skills. Two forms of input-output relation are described, both consistent with the cortical theory. One is suitable for learning movements (actions), and the other for learning to maintain posture and balance (maintenance reflexes).2. It is known that the cells of the inferior olive and the cerebellar Purkinje cells have a special one-to-one relationship induced by the climbing fibre input. For learning actions, it is assumed that:(a) each olivary cell responds to a cerebral instruction for an elemental movement. Any action has a defining representation in terms of elemental movements, and this representation has a neural expression as a sequence of firing patterns in the inferior olive; and(b) in the correct state of the nervous system, a Purkinje cell can initiate the elemental movement to which its corresponding olivary cell responds.3. Whenever an olivary cell fires, it sends an impulse (via the climbing fibre input) to its corresponding Purkinje cell. This Purkinje cell is also exposed (via the mossy fibre input) to information about the context in which its olivary cell fired; and it is shown how, during rehearsal of an action, each Purkinje cell can learn to recognize such contexts. Later, when the action has been learnt, occurrence of the context alone is enough to fire the Purkinje cell, which then causes the next elemental movement. The action thus progresses as it did during rehearsal.4. It is shown that an interpretation of cerebellar cortex as a structure which allows each Purkinje cell to learn a number of contexts is consistent both with the distributions of the various types of cell, and with their known excitatory or inhibitory natures. It is demonstrated that the mossy fibre-granule cell arrangement provides the required pattern discrimination capability.5. The following predictions are made.(a) The synapses from parallel fibres to Purkinje cells are facilitated by the conjunction of presynaptic and climbing fibre (or post-synaptic) activity.(b) No other cerebellar synapses are modifiable.(c) Golgi cells are driven by the greater of the inputs from their upper and lower dendritic fields.6. For learning maintenance reflexes, 2(a) and 2(b) are replaced by2'. Each olivary cell is stimulated by one or more receptors, all of whose activities are usually reduced by the results of stimulating the corresponding Purkinje cell.7. It is shown that if (2') is satisfied, the circuit receptor --> olivary cell --> Purkinje cell --> effector may be regarded as a stabilizing reflex circuit which is activated by learned mossy fibre inputs. This type of reflex has been called a learned conditional reflex, and it is shown how such reflexes can solve problems of maintaining posture and balance.8. 5(a), and either (2) or (2') are essential to the theory: 5(b) and 5(c) are not absolutely essential, and parts of the theory could survive the disproof of either.

Animals↗
PubMed1988

Perception of the immediate extrapersonal space through proprioceptive inputs.

In the present work we sought to examine the idea that an internalized representation of space can be formed and used in the absence of visual information. To this end human subjects were trained to locate 5 points within a horizontal plane at shoulder level, under guidance of an acoustic signal. Next, reaching accuracy was determined for both the trained and the untrained hands without external cues. This allowed comparison of hand positioning that could be based upon a memory trace or proprioceptive inputs (trained hand) to hand positioning that must be based upon a more abstract internal representation than proprioceptive memory (untrained hand). The effect of training on reach accuracy of the two hands and the effect of prolongation the time interval between guided and recall (unguided) trials were studied. Finally, subjects were asked to interpolate between already learned target positions, a procedure which tested their ability to utilize an abstract construct of space. The relative contribution of the elbow and shoulder joints to reaching errors was determined. This analysis served to evaluate whether representation of spatial locations was based on joint angle coordinates, or on a more abstract extracorporeal reference system. Our results indicate that a memorized sensory image of the limb, which corresponds to the hand being at the target position, is used whenever possible. An abstract representation of position is used whenever comparison of the actual sensory input to a memorized sensory trace is made impossible, costing an approximately 25% reduction in accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2003

Associative olfactory learning of honeybees to differential rewards in multiple contexts--effect of odor component and mixture similarity.

Discrimination among differentially rewarding flowers allows honeybees to maximize their foraging efficiency. We studied how honeybees are able to relate to differential positive rewards when the odor representations are either structurally dissimilar, structurally similar (or form a substrate-product duo in planta), or form a binary mixture sharing a common constituent. Bees were tested both in conditioning of the proboscis-extension response (PER) and in a free-flying context. Our results point to honeybees using olfactory associative learning to differentiate between two positively rewarded odors. In PER, subjects discriminated best between dissimilar odors; they initially generalized between similar odors, but eventually learned to discriminate between them. The discrimination between mixtures sharing a common constituent remained poor. Likewise, the difference in visits to low- and high-rewarding flowers of free-flying bees was greater for dissimilar odors than for binary mixtures sharing a common constituent. Consequences of the operant conditioning nature of the free-flying context are discussed.

Animals↗