Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “representation learning”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,513 records · Page 84Linked to original sources
PubMed2004

Seeing words in context: the interaction of lexical and sentence level information during reading.

The ERP experiment reported here addresses some outstanding questions regarding word processing in sentential contexts: (1) Does only the 'message-level' representation (the representation of sentence meaning combining lexico-semantic and syntactic constraints) affect the processing of the incoming word [J. Exp. Psychol.: Learn. Mem. Cogn. 20 (1994) 92]? (2) Is lexically specified semantic relatedness between multiple words the primary factor instead [J. Exp. Psychol.: Learn. Mem. Cogn. 15 (1989) 791]? (3) Alternatively, do word and sentence level information interact during sentence comprehension? Volunteers read sentences (e.g. Dutch sentences resembling The javelin was by the athletes...) in which the (passive) syntactic structure and the semantic content of the lexical items together created a strong expectation of a specific final word (e.g., thrown), but also sentences in which the syntactic structure was changed from passive to active (e.g. Dutch sentences resembling The javelin has the athletes...), which altered the message level constraint substantially and strongly reduced the expectation of any particular completion. Half of the sentences ended in a final word with a good lexico-semantic fit relative to the preceding content words (e.g. thrown, fitting well with the preceding javelin and athletes). This creates very plausible sentences in the strong constraint context but semantically anomalous ones in the weakly constraining context (e.g., The javelin has the athletes thrown). In the other half the final word had a poor lexico-semantic fit (e.g., summarized that does not fit at all with javelin and athletes). Good lexico-semantic fit endings showed no difference in N400 amplitude in the strong and weak message-level constraint sentences, despite the fact that the latter were semantically anomalous. This result suggests that lexico-semantic fit can be more important for word processing than the meaning of the sentence as determined by the syntactic structure, at least initially. These conditions did differ, however, in the region of the P600 where the anomalous weak constraint version was much more positive, a pattern usually seen with ungrammatical sentences. The processing of poor lexico-semantic fit words showed a quite different pattern; in both strong and weak constraint sentences they elicited a substantial N400 effect, but N400-amplitude was significantly more negative following strong constraint contexts, even though both sentence contexts were equivalently anomalous. Taken together, these findings provide evidence for the importance of both message-level and lexico-semantic information during sentence comprehension. The implications for theories of sentence interpretation are discussed and an extension of the message-based hypothesis will be proposed.

Adult↗
PubMed2007

Priming reveals differential coding of symbolic and non-symbolic quantities.

Number processing is characterized by the distance and the size effect, but symbolic numbers exhibit smaller effects than non-symbolic numerosities. The difference between symbolic and non-symbolic processing can either be explained by a different kind of underlying representation or by parametric differences within the same type of underlying representation. We performed a primed naming study to investigate this issue. Prime and target format were manipulated (digits or collections of dots) as well as the numerical distance between prime and target value. Qualitatively different priming patterns were observed for the two formats, showing that the underlying representations differed in kind: Digits activated mental number representations of the place coding type, while collections of dots activated number representations of the summation coding type.

Adult↗
PubMed1999

The visual representation of three-dimensional, rotating objects.

Depth rotations can reveal new object parts and result in poor recognition of "static" objects (Biederman & Gerhardstein, 1993). Recent studies have suggested that multiple object views can be associated through temporal contiguity and similarity (Edelman & Weinshall, 1991; Lawson, Humphreys & Watson, 1994; Wallis, 1996). Motion may also play an important role in object recognition since observers recognize novel views of objects rotating in the picture plane more readily than novel views of statically re-oriented objects (Kourtzi & Shiffrar, 1997). The series of experiments presented here investigated how different views of a depth-rotated object might be linked together even when these views do not share the same parts. The results suggest that depth rotated object views can be linked more readily with motion than with temporal sequence alone to yield priming of novel views of 3D objects that fall in between "known" views. Motion can also enhance path specific view linkage when visible object parts differ across views. Such results suggest that object representations depend on motion processes.

Adult↗
PubMed1999

Speech sound perception, neurophysiology, and plasticity.

An approach to understanding biological processes underlying speech perception, is to discover how speech sounds are represented in the central auditory system and to relate that representation to the perception of speech as a meaningful acoustic signal. Research from our group that pertains to the neurophysiologic representation of speech in the central pathways is reviewed here. Specifically considered is the relation between the representation of sound in the auditory pathway and the perception/misperception of speech, and neurophysiologic plasticity associated with speech-sound perceptual learning.

Auditory Pathways↗
PubMed2003

Does the radial arm maze necessarily test spatial memory?

Since its design 25 years ago (Olton & Samuelson, 1976), the eight-arm radial maze has become very popular and is now widely used to assess spatial memory in rodents. Two versions of the full-baited maze protocol are present in the literature: with or without confinement between the visit of each arm. The confinement was introduced by Olton himself as early as 1977 (Olton, Collison, & Werz, 1977) to eliminate stereotypic behaviors that he had previously observed. It is widely regarded that the confinement prevents rodents from developing these response patterns, and as such it is considered an improved procedure to test spatial memory. Surprisingly, to the best of our knowledge, no study has been especially designed to demonstrate the efficacy of the confinement in blocking the stereotypic behaviors of the animals. The present study compares the strategies of rats trained with or without a confinement procedure. The results show that, after nine days of training, rats submitted to a 5- or a 10-s confinement reach the same level of performance as rats without confinement. The confinement totally prevents stereotypic behaviors like clockwise serial searching strategies which are often observed without confinement. Even a 0-s confinement is sufficient to prevent clockwise strategies, but rats seem to develop other stratagems which do not imply spatial memory. Furthermore, rats previously trained without confinement are unable to perform the task when confinement is introduced on a test day. In contrast, rats previously trained with confinement perform the task correctly when the confinement is no longer present. Thus, without confinement, good levels of performance can be achieved without precise spatial representations.

Animals↗
PubMed2005

Love hurts: the evolution of empathic concern through the encephalization of nociceptive capacity.

Empathic concern for others is an essential motive for challenges of self-regulation at all developmental stages. A child who never develops the capacity for empathic concern may become an ineffective parent, such that developmental psychopathology propagates across generations. We draw on evidence and theory by Panksepp and associates that indicates that infant-mother bonding is mediated by opiate mechanisms. We review the neural systems of pain perception and find these are closely aligned with those for attentional and cognitive self-regulation. Analysis of the limbic and neocortical representations for interpersonal reasoning suggests there are important contributions from visceral, affective, and somatic and cognitive levels. We draw on modern learning theory to propose a critical role for frustration training in development to allow the child to achieve the capacity for tolerating psychological pain that allows effective empathic concern in later relationships.

Attention↗
PubMed1987

Visual knowledge underlying letter perception: font-specific, schematic tuning.

The representation of visual information about letters is proposed to be highly systematic, involving not only abstract information that is invariant across type faces (or fonts), but also a number of parameters whose values are determined by the current font. The system exploits regularities that are characteristic of letters and fonts by becoming tuned to the details of the font. This should result in efficient letter perception when the stimuli are regular (when all of the letters are of a consistent font), but not when the stimuli are irregular (when the letters are from a variety of fonts). The prediction of faster processing with a regular font, as compared with a mixed font, was examined in three experiments requiring the recognition of four-letter strings. Experiment 1 confirmed the prediction, and Experiment 2 replicated the effect with the number of "features" equated across conditions. Experiment 3 showed that the disadvantage for a mixture of fonts is related to how much the representational system must be adjusted to handle the different fonts.

Attention↗
PubMed1996

Conceptual effects on representational momentum.

Four experiments addressed the question of whether prior knowledge of an object's typical movement in the real world affects the representation of motion. Representational momentum (RM) is the tendency for the short-term memory representation of an object to undergo a transformation corresponding to the object's trajectory. Using the standard RM paradigm, the RM elicited by objects with different typical motions was compared. Results indicate that conceptual knowledge about an object's typical motion affects the magnitude of RM and, as such, the representation of motion.

Adult↗
PubMed2002

Dissociation of explicit and implicit timing in repetitive tapping and drawing movements.

Four experiments explored the hypothesis that temporal processes may be represented and controlled explicitly or implicitly. Tasks hypothesized to require explicit timing were duration discrimination, tapping, and intermittent circle drawing. In contrast, it was hypothesized that timing control during continuous circle drawing does not rely on an explicit temporal representation; rather, temporal control is an emergent property of other control processes (i.e., timing is controlled implicitly). Temporal consistency on the tapping and intermittent drawing tasks was related, and performance on both of these tasks was correlated with temporal acuity on an auditory duration discrimination task. However, timing variability of these 3 tasks was not correlated with timing variability of continuous circle drawing. These results support the hypothesized distinction between explicit and implicit temporal representations.

Adolescent↗
PubMed1989

Categorizing objects in isolation and in scenes: what a superordinate is good for.

Many studies have shown that subjects are faster at categorizing objects into "basic" concepts than into more general superordinate concepts. However, all of these studies have used a categorization task in which single, isolated objects are identified. There is good reason to believe that superordinate concepts are typically used to refer to collections of objects rather than to individual objects. For example, people more often use the term furniture to refer to a number of pieces of furniture rather than to name a single piece. This suggest that superordinate concepts include information about multiple objects and their common relations, particularly the typical scenes in which such objects appear. Four experiments examined this possibility by investigating whether the basic concept advantage will decrease or reverse itself when subjects are asked to categorize an object as part of a scene. The results showed that the basic-superordinate difference did decrease when subjects categorized objects in scenes. Furthermore, when an object was placed in an inappropriate scene, there was more interference for superordinate identifications. The results suggest qualitative differences in the representations of superordinate and basic concepts.

Adult↗
PubMed2002

The roles of body and mind in abstract thought.

How are people able to think about things they have never seen or touched? We demonstrate that abstract knowledge can be built analogically from more experience-based knowledge. People's understanding of the abstract domain of time, for example, is so intimately dependent on the more experience-based domain of space that when people make an air journey or wait in a lunch line, they also unwittingly (and dramatically) change their thinking about time. Further, our results suggest that it is not sensorimotor spatial experience per se that influences people's thinking about time, but rather people's representations of and thinking about their spatial experience.

Adult↗
PubMed2005

The site of a motor memory shifts with consolidation.

The basis for the consolidation of memory is a controversial topic, particularly in the case of motor memory. One view is that motor memory is transferred, partially or completely, to a new location during the consolidation process ("systems consolidation"). We investigated this possibility in a primitive motor system, the vestibulo-ocular reflex (VOR). In the simple circuitry of the VOR, there are relatively few possible storage sites for memory. We partially blocked excitatory neurotransmission in the cerebellar cortex of cats with the glutamate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). If CNQX was injected immediately after 60 min of rotation under conditions that induced a learned decrease in the gain of the VOR, gain was returned to its baseline value. Expression of the new memory could also be disrupted by rotation in darkness, suggesting that consolidation had not taken place; however, after learning had continued for 3 d, expression of the learned change was diminished only slightly by blockade and was unaffected by rotation in darkness. Our interpretation of these results is that learning may take place initially in the cerebellar cortex and that during consolidation, motor memories are converted to a more distributed representation that includes the cerebellar cortex and another site.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2003

Incidental formation of episodic associations: the importance of sentential context.

The influence of relevant semantic context on the incidental formation of episodic associations between words was probed in two experiments. In Experiment 1, we examined the influence of associations formed incidentally between unrelated words presented either in isolation or embedded in a sentential context on subsequent explicit paired-associate leaning tested by cued recall. The results of Experiment 1 showed that the cued-recall rate of words studied in sentential context was higher than that of words co-occurring in isolated pairs. A subsequent single-items recognition test showed equal item memory for words studied in sentences than for words studied in isolated pairs, suggesting that the sentential context effect in cued recall indeed reflected stronger associations between paired words rather than better memory for single words. In Experiment 2, we ruled out memory for the entire sentence as an alternative explanation for the results of Experiment 1. We suggest two possible mechanisms to account for this advantage: First, pairs embedded in a sentence undergo semantic elaboration that might lead to the incidental formation of an association between them. Second, words embedded in a sentence enjoy the conjoint activation of compatible semantic features, a fact that may also facilitate the formation of an episodic association between them. The implications of these results for computational models using word representations based on co-occurrence data are discussed.

Humans↗
PubMed2003

A primitive memory system for the deployment of transient attention.

When transient attention is summoned by the sudden appearance of a large cue, it can be deployed to a small portion of the cue where a target appeared on previous trials (Kristjánsson, Mackeben, & Nakayama, 2001). This result runs counter to the view that transient, or exogenous, attention is summoned automatically and indiscriminately to abruptly appearing stimuli. To further characterize the short-term learning mediating this phenomenon, we report the following results. (1) When there was a consistent relationship between a small identifying portion of the cue and the target, learning occurred rapidly. Thus, transient attention can be summoned to a distinctively colored or distinctively shaped portion of the cue as a consequence of repeated pairing (Experiments 1 and 2). (2) When there was a consistent relation between a given position on the object and its overall color or shape, no learning occurred (Experiments 3 and 4). Thus, transient attention cannot learn a complex relation between target position and shape or color. (3) We confirmed the fast object-centered learning of position shown in Kristjánsson et al. (2001). (4) Explicit knowledge of the cue-target relationship had no effect on the performance of the task. The results provide evidence for the existence of a primitive object-centered learning mechanism beneficial for the rapid deployment of transient attention. The possible role of such a mechanism in the maintenance of representations of the visual environment is discussed.

Attention↗
PubMed2002

Volatile visual representations: failing to detect changes in recently processed information.

Research documenting people's inability to detect large changes in visual scenes suggests that visual representations may be sparse and volatile, providing no cumulative record of the attended items in a scene. However, these studies have failed to control for attention. Thus, the visual system may construct a cumulative record of all attended stimuli and still miss such changes, because they involve items that were never attended to. In two experiments, subjects saw 12-digit arrays and identified either the highest digit in the array (Experiment 1) or the lowest digit not in the array (Experiment 2). Subsequent change-detection tasks revealed that subjects often failed to detect changes that involved the same digits they had previously identified to perform the digit tasks successfully. This provides additional evidence that our usable visual representations are relatively impoverished and volatile.

Adult↗
PubMed2000

Visualization of multiple influences on ocellar flight control in giant honeybees with the data-mining tool Viscovery SOMine.

Viscovery SOMine is a software tool for advanced analysis and monitoring of numerical data sets. It was developed for professional use in business, industry, and science and to support dependency analysis, deviation detection, unsupervised clustering, nonlinear regression, data association, pattern recognition, and animated monitoring. Based on the concept of self-organizing maps (SOMs), it employs a robust variant of unsupervised neural networks--namely, Kohonen's Batch-SOM, which is further enhanced with a new scaling technique for speeding up the learning process. This tool provides a powerful means by which to analyze complex data sets without prior statistical knowledge. The data representation contained in the trained SOM is systematically converted to be used in a spectrum of visualization techniques, such as evaluating dependencies between components, investigating geometric properties of the data distribution, searching for clusters, or monitoring new data. We have used this software tool to analyze and visualize multiple influences of the ocellar system on free-flight behavior in giant honeybees. Occlusion of ocelli will affect orienting reactivities in relation to flight target, level of disturbance, and position of the bee in the flight chamber; it will induce phototaxis and make orienting imprecise and dependent on motivational settings. Ocelli permit the adjustment of orienting strategies to environmental demands by enforcing abilities such as centering or flight kinetics and by providing independent control of posture and flight course.

Animals↗
PubMed1997

The perception of shape and curvedness from binocular stereopsis and structure from motion.

The integration of binocular stereopsis and kinetic depth was measured for two distinct aspects of 3-D structure: (1) shape index, which is a measure of scale-independent structure, and (2) curvedness, which is a measure of scale-dependent structure. We found that motion contributes significantly more to judged shape index than it does to judged curvedness, and stereo contributes significantly more to judged curvedness than it does to judged shape index. This suggests that the differences in the relative contribution of motion and stereo reported here occurred because these two sources do not equally specify the scale-dependent and scale-independent aspects of surface structure. Furthermore, these results seem to be inconsistent with integration models in which the different visual cues all initially contribute to the same single representation of 3-D structure.

Depth Perception↗
PubMed1984

[Selective stabilization of neuronal representations by resonance between spontaneous prerepresentations of the cerebral network and percepts evoked by interaction with the outside world].

Changeux et al. (Changeux, Heidmann and Patte, in "The Biology of Learning" Dahlem Conference, 1984, pp. 115-133, Springer Verlag) have recently discussed a model of "learning by selection" in which the storage of patterns of activity--or prerepresentations--within a network of neurons, results from the coincidence or "resonance" between a spontaneous activity of the neurons and external signals applied to the network--for instance sensory stimuli. In this Note, a mathematical formulation of the model is presented, based on that proposed by Little and Shaw (Little, Math. Biosci., 19, 1974, pp. 101-120; Little and Shaw, Math. Biosci., 39, 1978, pp. 281-290) for the statistical analysis of neuronal activity within a network, and on a rule for modulation of synaptic efficacies derived from that proposed by Hebb (Hebb, The Organisation of Behaviour, 1949, Wiley). The effect of an external signal sigma on the probability P(beta) of occurrence of a given prerepresentation beta under stationary conditions has been analytically derived [cf. equation (16) in text]. Taking into account that the system spontaneously fluctuates between various prerepresentations, it is shown that P(beta) is increased by the external signal sigma when (1) beta is close to sigma--namely the external signal significantly modifies the probabilities of those prerepresentations that resemble sigma--, and (2) when the external signal sigma sets the neurons precisely in the state that they would have more probably reached at the moment when the external signal was applied. Namely there should exist a "resonance" between sigma and the prerepresentation of the network when sigma is applied.

Animals↗