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 1,279 records · Page 71Linked to original sources
PubMed2000

Phonology acquired through the eyes and spelling in deaf children.

Hearing and deaf children, ranging in age from 6 years 8 months to 14 years 4 months, and matched for general spelling level, were required to spell high-frequency and low-frequency words. Of interest was performance in relation to degree of exposure to Cued Speech (CS), which is a system delivering phonetically augmented speechreading through the visual modality. Groups were (a) hearing children, (b) deaf children exposed early and intensively to CS at home (CS-Home), and (c) deaf children exposed to CS later and at school only (CS-School). Most of the spelling productions of hearing children as well as of CS-Home children were phonologically accurate for high-frequency as well as for low-frequency words. CS-School children, who had less specified phonological representations, made a lower proportion of phonologically accurate spellings. These findings indicate that the accuracy of phonological representations, independent of the modality (acoustic versus visual) through which spoken language is perceived, determines the acquisition of phonology-to-orthography mappings. Analyses of the spelling productions indicate that the acquisition of orthographic representations of high precision depends on fully specified phonological representations.

Child↗
PubMed2000

Effects of environmental enrichment on rate of contextual processing and discriminative ability in adult rats.

The effect of environmental enrichment on conditioned freezing to contextual cues in adult Sprague-Dawley rats was examined. The freezing of both enriched-and standard-reared rats increased with the time spent in the chamber prior to shock. Both groups of rats showed equally low levels of contextual conditioning following a preshock period of 4 s and equally high levels following a 120-s preshock period. However, following a preshock period of 16 s enriched rats displayed more contextual conditioning than standard rats. That is, enriched rats appeared to process contextual information faster than their standard-reared counterparts. Enriched- reared rats also showed a greater ability to discriminate between the conditioning context and a similar but distinctive context. Hence, in addition to forming a representation of the context in memory more rapidly than standard-reared rats, enriched-reared rats also appear to form a more complex representation.

Age Factors↗
PubMed2002

Automatic integration of non-perceptual action effect features: the case of the associative affective Simon effect.

In the first phase of Experiment 1, participants were instructed to move a response key up or down in response to a go signal. One of both responses was consistently followed by an aversive stimulus, whereas the other response was never followed by the aversive stimulus. In a subsequent test phase, the same responses had to be emitted according to the grammatical category (noun or adjective) of positive and negative target words. Results showed that the level of affective correspondence between the task-irrelevant positive or negative connotation of the target and the motivational significance of the effect of the correct response influenced performance. The results of Experiment 2 replicated those of Experiment 1, using alternating target-response assignment. These findings point to the integration of affective action effect feature codes in the cognitive representation of actions.

Association Learning↗
PubMed2002

Representing task context: proposals based on a connectionist model of action.

Representations of task context play a crucial role in shaping human behavior. While the nature of these representations remains poorly understood, existing theories share a number of basic assumptions. One of these is that task representations are discrete, independent, and non-overlapping. We present here an alternative view, according to which task representations are instead viewed as graded, distributed patterns occupying a shared, continuous representational space. In recent work, we have implemented this view in a computational model of routine sequential action. In the present article, we focus specifically on this model's implications for understanding task representation, considering the implications of the account for two influential concepts: (1) cognitive underspecification, the idea that task representations may be imprecise or vague, especially in contexts where errors occur, and (2) information-sharing, the idea that closely related operations rely on common sets of internal representations.

Behavior↗
PubMed1996

Basic-level and superordinate-like categorical representations in early infancy.

A series of experiments using the paired-preference procedure examined 3- to 4-month-old infants' ability to form perceptually based categorical representations in the domains of natural kinds and artifacts and probed the underlying organizational structure of these representations. Experiments 1 and 2 found that infants could form categorical representations for chairs that excluded exemplars of couches, beds, and tables and also for couches that excluded exemplars of chairs, beds, and tables. Thus, the adult-like exclusivity shown by infants in the categorization of various animal pictures at the basic-level extends to the domain of artifacts as well--an ecologically significant ability given the numerous artifacts that populate the human environment. Experiments 3 and 4 examined infants' ability to form superordinate-like or global categorical representations for mammals and furniture. It was found that infants could form a global representation for mammals that included novel mammals and excluded other non-mammalian animals such as birds and fish as well as items from cross-ontological categories such as furniture. In addition, it was found that infants formed a representation for furniture that included novel categories of furniture and excluded exemplars from the cross-ontological category of mammals; however, it was less clear if infants' global representation for furniture also excluded other artifacts such as vehicles and thus the category of furniture may have been less exclusively represented. Overall, the present findings, by showing the availability of perceptually driven basic and superordinate-like representations in early infancy that closely correspond to adult conceptual categories, underscore the importance of these early representations for later conceptual representations.

Adult↗
PubMed2000

Involvement of the hippocampus and associative parietal cortex in the use of proximal and distal landmarks for navigation.

Rats with dorsal hippocampus or associative parietal cortex (APC) lesions and sham-operated controls were trained on variants of the Morris water maze navigation task. In the 'proximal landmark condition', the rats had to localize the hidden platform solely on the basis of three salient object landmarks placed directly in the swimming pool. In the 'distal landmark condition', rats could rely only on distal landmarks (room cues) to locate the platform. In the 'beacon condition', the platform location was signaled by a salient cue directly attached to it. Rats with hippocampal lesions were impaired in the distal and to a less extent in the proximal landmark condition whereas rats with parietal lesions were impaired only in the proximal landmark condition. None of the lesioned groups was impaired in the beacon condition. These results suggest that the processing of information related to proximal, distal landmarks or associated beacon are mediated by different neural systems. The hippocampus would contribute to both proximal and distal landmark processing whereas the APC would be involved in the processing of proximal landmarks only. Navigation relying on a cued-platform would not require participation of the hippocampus nor the APC. Assuming that the processing of proximal landmarks heavily depends on the integration of visuospatial and idiothetic information, these results are consistent with the hypothesis that the APC plays a role in the combination of multiple sensory information and contributes to the formation of an allocentric spatial representation.

Animals↗
PubMed1994

Does orientation-independent object recognition precede orientation-dependent recognition? Evidence from a cuing paradigm.

Object recognition may entail an incremental normalization process before access to canonical orientation representations, but is this process guided by prior access to object-centered representations? In Experiment 1, the authors showed observers figure-ground stimuli known to reflect access to, and output from, stored shape representations. The stimuli appeared in each of 6 different orientations, preceded by cues providing either (a) no information, (b) upright shape information only, (c) upright shape information plus orientation information (separately), or (d) shape information in the same orientation as the upcoming figure-ground test stimulus. Contrary to predictions by a postaccess account, the cues failed to eliminate orientation dependency in shape recognition. The results favor a preaccess account of the normalization process within the context of canonical orientation representations.

Adult↗
PubMed1998

Effects of orientation on the identification of rotated objects depend on the level of identity.

Matching names and rotated line drawings of objects showed effects of object orientation that depended on name level. Large effects, in the same range as object naming, were found for rotations between 0 degrees and 120 degrees from upright with subordinate names (e.g., collie), whereas nonsignificant effects were found with superordinate (e.g., animal) and basic names (e.g., dog). These results support image normalization, after contact with orientation-invariant representations, that provide basic-level identity. They consequently fail to support theories of object recognition in which rotated object images are normalized to the upright position before contact with long-term object representations.

Adolescent↗
PubMed1995

Attention, automaticity, and levels of representation in number processing.

Participants performed same-different judgments for pairs of numerals in 2 conditions: numerical matching (responding "same" to pairs such as 2-TWO), or physical matching (responding "different" to pairs such as 2-TWO). In most cases, a distance effect was obtained, with the different responses being slower when the 2 numbers were numerically close together (e.g., 1-2) than when they were further apart (e.g., 1-8). This indicates that numbers were automatically converted mentally into quantities, even when the participants had been told to attend exclusively to their physical characteristics. As postulated by several models of number processing, (e.g., Dehaene, 1992; McCloskey, 1992) Arabic and verbal numerals thus appear to converge toward a common semantic representation of quantities. However, the present results suggest that an asemantic transcoding route might allow for a direct mapping of Arabic and verbal numbers, perhaps by means of a common phonological representation.

Adolescent↗
PubMed1992

N-methyl-D-aspartate receptor antagonist MK-801 and spatial memory representation: working memory is impaired in an unfamiliar environment but not in a familiar environment.

Female Sprague-Dawley rats were injected with the noncompetitive N-methyl-D-aspartate (NMDA) antagonist MK-801 or saline 30 min before daily testing in spatial working memory (WM) and reference memory (RM) procedures in an 8-arm radial maze. MK-801 impaired RM and WM acquisition but not performance when rats were trained to criterion before drug administration. Neither a 2-hr nor a 4-hr delay between the first and last 2 correct WM choices impaired long-term WM. MK-801 impaired WM performance in trained rats only when rats were tested in a new environment. Thus, 2 mechanisms may be required for relational memory: an NMDA-dependent mechanism for acquiring long-term spatial representations and an NMDA-insensitive mechanism for operating on these stored representations.

Animals↗
PubMed1984

Stimulus equivalence after inferior temporal lesions in monkeys.

Monkeys with inferior temporal cortex lesions and unoperated monkeys were trained to discriminate pairs of objects and then tested for transfer after the original discriminanda were made larger or smaller, rotated, or presented as two-dimensional projections. The two groups of monkeys transferred equally well to the discriminanda altered in size or orientation, but only the unoperated animals transferred to the two-dimensional representation.

Animals↗
PubMed2005

Interactions between conditioned and unconditioned flavor preferences.

Five experiments investigated how rats' conditioned preferences or aversions for aqueous odors paired with sucrose or salt are affected by their unconditioned response to those tastes. Rats preferred an odor paired with 30% sucrose over an odor paired with 5% sucrose when both were presented in 5% sucrose, but they showed no preference or, if thirsty, showed the reverse preference, when the odors were presented in 30% sucrose. These changes in conditioned preference corresponded to changes in the rats' unconditioned preference for the accompanying sucrose solution. Rats' conditioned aversions for odors paired with salt showed a similar dependence on their reaction to the accompanying salt solution. The results were interpreted as showing that conditioned and unconditioned flavor preferences combine additively, as if mediated by the same sensory representation.

Analysis of Variance↗
PubMed2006

Picture-object recognition in pigeons: evidence of representational insight in a visual categorization task using a complementary information procedure.

Success in tasks requiring categorization of pictorial stimuli does not prove that a subject understands what the pictures stand for. The ability to achieve representational insight is by no means a trivial one because it exceeds mere detection of 2-D features present in both the pictorial images and their referents. So far, evidence for such an ability in nonhuman species is weak and inconclusive. Here, the authors report evidence of representational insight in pigeons. After being trained on pictures of incomplete human figures, the birds responded significantly more to pictures of the previously missing parts than to nonrepresentative stimuli, which demonstrates that they actually recognized the pictures' representational content.

Animals↗
PubMed1997

Declarative memory: insights from cognitive neurobiology.

The discovery of declarative memory as distinct from other forms of memory is a major recent achievement in cognitive science. Basic issues about the nature of declarative memory are considered in this review from the perspective of studies on its underlying brain mechanisms. These studies have shown that declarative memory is mediated by a specific brain system including areas of the cerebral cortex and hippocampal region that make distinct functional contributions to memory processing. These processing mechanisms mediate the organization of memories in ways that can support the special properties of declarative or explicit memory expression. Furthermore, the basic properties of declarative memory in human beings can be viewed as evolving from a capacity for organized memory representation and flexible memory expression in animals.

Animals↗
PubMed1989

Selectional processes in causality judgment.

Two experiments illustrate the way in which competition between potential causes occurs when subjects are asked to judge the extent to which an action is the cause of an outcome. In the first experiment, it was found that introducing occurrences of the outcome in the absence of the action reduced causality judgments, but this effect was attenuated if these outcomes were signaled by another stimulus. In the second experiment, a delay between the action and the outcome reduced judgments, but this could be abolished by inserting a stimulus between the action and the outcome. The results are discussed in terms of a view of causality judgment that assumes that such judgments are based on associations between the mental representations of the action and the outcome.

Association Learning↗
PubMed2000

Perceptual reference points for form and orientation in young infants: anchors or magnets?

In some domains, certain stimuli are especially salient and efficiently encoded and are referred to as reference points. One current issue concerns whether reference points are associated with regions of increased or decreased discriminability and function as either perceptual anchors or magnets. In two experiments utilizing the familiarization/novelty-preference procedure, the question of whether 3- to 4-month-old infants' representations of form and orientation information are structured by perceptual reference points and whether such reference points serve as anchors or magnets is examined. In Experiment 1, infants displayed above-chance discrimination performance for pairs of form stimuli that were equivalently distinct on a physical basis, but only when one member of each pair was a "good" form (i.e., diamond, square, or triangle). In Experiment 2, infants displayed above-chance discrimination performance for pairs of stimuli differing by 7.5 degrees of orientation, but only when one member of each pair was either horizontal or vertical. The combined results from the two experiments suggest that "simple" gestalts and main axes (i.e., horizontal and vertical) serve as perceptual anchors in young infants' representations of form and orientation information.

Attention↗
PubMed1997

Naloxone impairs spatial performance in rats.

Naloxone-injected (1.0 mg/kg) and saline-injected control rats were subjected to a two-trial test of object localization memory. In trial I rats were allowed to explore for 5 min an enclosed T-maze with an object (plastic bottle) placed in one maze arm. Then, the object was removed and after a 20-min retention interval rats were faced with two empty arms of the same maze (trial II). Control rats showed good retention of the place occupied by the object, displaying a significant preference (74%, P < 0.032) for the arm which previously contained the object. Naloxone treated rats responded at chance levels (53%). An accurate performance in this task is normally based on information provided by spatial cues outside the maze (cognitive map), so that a random performance of Naloxone treated rats could supposedly be related to some disorders in the internal representation of the environment.

Animals↗
PubMed1990

Stimulus generalization as a function of stimulus novelty and familiarity in rats.

Three experiments used rats as subjects to investigate the generalization of conditioned responding between stimuli as a function of the subjects' exposure to these cues prior to conditioning. Experiment 1 used a between-subjects design, food as the reinforcer, and measured the tendency of subjects to approach the site of food delivery during the stimuli. Generalization of this response was more marked when the training and test stimuli were equated in terms of their novelty (i.e., when both were novel or both were familiar) than when the stimuli differed in this respect (i.e., when one was novel and the other was familiar). Experiments 2a and 2b used within-subjects designs to confirm the reliability of the results of Experiment 1. Implications of these results for current theories of stimulus representation are discussed.

Animals↗