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PubMed1987

Application of a cognitive-distance model to learning in a simulated travel task.

A cognitive-distance model for choice, obtained by specializing a general class of models for categorization, was tested in a situation simulating the task of controlling speed of a vehicle in tasks defined by different relations between speed and probability of delay. Subjects exhibited significant learning whenever delay schedules permitted greater-than-chance performance, but on the average they did not approach optimal performance in the sense of choosing speeds so as to maximize distance attained in allowed time. Evidence was obtained that subjects encoded information about probabilities of delay and distributions of distance attained at different speeds quite accurately in memory and that suboptimal performance was due primarily to imperfect discrimination among representations of choice alternatives on a cognitive scale of expected distance.

Adult↗
PubMed2006

A connectionist computational model for epistemic and temporal reasoning.

The importance of the efforts to bridge the gap between the connectionist and symbolic paradigms of artificial intelligence has been widely recognized. The merging of theory (background knowledge) and data learning (learning from examples) into neural-symbolic systems has indicated that such a learning system is more effective than purely symbolic or purely connectionist systems. Until recently, however, neural-symbolic systems were not able to fully represent, reason, and learn expressive languages other than classical propositional and fragments of first-order logic. In this article, we show that nonclassical logics, in particular propositional temporal logic and combinations of temporal and epistemic (modal) reasoning, can be effectively computed by artificial neural networks. We present the language of a connectionist temporal logic of knowledge (CTLK). We then present a temporal algorithm that translates CTLK theories into ensembles of neural networks and prove that the translation is correct. Finally, we apply CTLK to the muddy children puzzle, which has been widely used as a test-bed for distributed knowledge representation. We provide a complete solution to the puzzle with the use of simple neural networks, capable of reasoning about knowledge evolution in time and of knowledge acquisition through learning.

Algorithms↗
PubMed2000

Representations of dread: the dreaded self and the dreaded state of the self.

The experience of dread, an extreme form of fear that is induced by terror and horror, is seen as manifested in the shapes of a "dreaded self" and a "dreaded state of the self." These representations reflect psychic dangers ranging from a common, feared identification to states of disconnection, desolation, ego dissolution, and nonexistence. It is suggested that life crises and traumatic impingements, informed by developmental and psychic realities, are critical determinants of multiple dreaded self-representations; that disavowal often serves to massively ward off the recognition of the awful; and that these representations serve a preconscious signal function that anticipates the danger of reexperiencing an original terror. Case examples illustrate these points and reflect the utility of the language of dreaded representations in the treatment situation.

Adult↗
PubMed2003

Desert ant navigation: how miniature brains solve complex tasks.

This essay presents and discusses the state of the art in studies of desert ant (Cataglyphis) navigation. In dealing with behavioural performances, neural mechanisms, and ecological functions these studies ultimately aim at an evolutionary understanding of the insect's navigational toolkit: its skylight (polarization) compass, its path integrator, its view-dependent ways of recognizing places and following landmark routes, and its strategies of flexibly interlinking these modes of navigation to generate amazingly rich behavioural outputs. The general message is that Cataglyphis uses path integration as an egocentric guideline to acquire continually updated spatial information about places and routes. Hence, it relies on procedural knowledge, and largely context-dependent retrieval of such knowledge, rather than on all-embracing geocentred representations of space.

Animals↗
PubMed1996

Differential environmental modulations on locomotor activity, exploration and spatial behaviour in young and old rats.

The effects of environmental enrichment on motor activity, exploration and spatial performances were studied in young and old rats. Both young (4 mo old) and old (22 mo old) rats were housed from weaning to testing either in standard or in enriched conditions. All rats were submitted successively to spontaneous alternation test and to object exploration test. Results show that locomotion is decreased by age and enrichment but that the quality of exploration expressed by corrected alternation scores or by the response to spatial change is improved by enrichment sometimes in old, sometimes in young rats. Enrichment tends to accelerate the acquisition of spatial informations in young rats, but it does not succeed to restore the reactivity to spatial change of old rats in the object exploration test. These results, although they do not rule out a persistance of a continued behavioural plasticity during aging, also support the idea that the beneficial effects of environmental stimulations do not succeed to restore high cognitive function, such as the capacity to have a spatial representation, in old animals.

Aging↗
PubMed2004

Word meaning and the control of eye fixation: semantic competitor effects and the visual world paradigm.

When participants are presented simultaneously with spoken language and a visual display depicting objects to which that language refers, participants spontaneously fixate the visual referents of the words being heard [Cooper, R. M. (1974). The control of eye fixation by the meaning of spoken language: A new methodology for the real-time investigation of speech perception, memory, and language processing. Cognitive Psychology, 6(1), 84-107; ]. We demonstrate here that such spontaneous fixation can be driven by partial semantic overlap between a word and a visual object. Participants heard the word 'piano' when (a) a piano was depicted amongst unrelated distractors; (b) a trumpet was depicted amongst those same distractors; and (c), both the piano and trumpet were depicted. The probability of fixating the piano and the trumpet in the first two conditions rose as the word 'piano' unfolded. In the final condition, only fixations to the piano rose, although the trumpet was fixated more than the distractors. We conclude that eye movements are driven by the degree of match, along various dimensions that go beyond simple visual form, between a word and the mental representations of objects in the concurrent visual field.

Association Learning↗
PubMed2006

Representations of familiar and unfamiliar faces as revealed by viewpoint-aftereffects.

A viewpoint-dependent aftereffect occurs after prolonged viewing of a stimulus of a particular orientation, with the result that the test image is perceived to be facing away from the adapting orientation. Prior psychophysical work has led to the suggestion that the visual brain encodes a limited range of viewpoint information with regard to complex images. In this study, we investigated whether familiar faces were susceptible to a viewpoint aftereffect. Familiar faces are believed to be represented in a view-invariant manner, whereas unfamiliar faces are represented in a viewpoint-dependent manner. Adaptation to both familiar and unfamiliar faces influenced the perception of viewpoint of subsequent face images. However, category-specific transfer of a repulsive viewpoint-dependent aftereffect was observed with unfamiliar faces. Our results suggest that neural networks that mediate viewpoint information are also involved in view-invariant representation of familiar faces.

Adult↗
PubMed1987

Hippocampal associative cellular responses: dissociation with behavioral responses revealed by a transfer-of-control technique.

Multiunit activity was recorded in the CA3 field of the dorsal hippocampus in freely moving rats during classical conditioning and subsequent presentation of the CS on operant baselines for food reward as well as shock avoidance. Rats were first trained in a nonsignaled bar-pressing-dependent shock omission task and in a food-motivated lever-pressing task (60-s VI). Five sessions with presentations of a previously habituated tone as a CS paired with footshock as a US were then given. Testing was carried out by presenting the CS alone while behavioral responses were maintained by reinforcement in both instrumental tasks on alternate sessions. As expected, the CS induced a marked suppression of lever pressing for food reward and a marked enhancement of bar-pressing for shock avoidance. The analysis of the frequency of multiunit discharges to the CS revealed that the hippocampal cellular responses established during classical conditioning were maintained while two different behavioral responses were exhibited to the CS. The results showed that the associative response of hippocampal neurons may be dissociated from the Pavlovian conditioned responses the CS elicits. They support the hypothesis that hippocampal cellular responses represent a neural index of the acquired CS-US associative representation.

Animals↗
PubMed1982

Representations of qualitative and quantitative dimensions.

Geometric representations of psychological dimensions are analyzed and compared to an alternative set-theoretical approach. Judgments of similarity between forms and figures reveal the following effects: (a) qualitative attributes are curved relative to quantitative attributes, contrary to intradimensional subtractivity; (b) quantitative attributes augment differences in qualitative attributes, contrary to interdimensional additivity; (c) adding a new dimension with a fixed value increases similarity, contrary to translation invariance. The implications of these results to multidimensional representations of proximity data are discussed.

Adolescent↗
PubMed1996

Object representation in the bottlenose dolphin (Tursiops truncatus): integration of visual and echoic information.

A dolphin performed a 3-alternative matching-to-sample task in different modality conditions (visual/echoic, both vision and echolocation: visual, vision only; echoic, echolocation only). In Experiment 1, training occurred in the dual-modality (visual/echoic) condition. Choice accuracy in tests of all conditions was above chance without further training. In Experiment 2, unfamiliar objects with complementary similarity relations in vision and echolocation were presented in single-modality conditions until accuracy was about 70%. When tested in the visual/echoic condition, accuracy immediately rose (95%), suggesting integration across modalities. In Experiment 3, conditions varied between presentation of sample and alternatives. The dolphin successfully matched familiar objects in the cross-modal conditions. These data suggest that the dolphin has an object-based representational system.

Animals↗
PubMed1990

Lexical priming from partial-word previews.

Two naming and two lexical decision experiments examined the use of partial-word preview in visual word recognition. Replicating results of an earlier reading study, the results of Experiments 1 and 2 revealed significant benefits from position-specific beginning- and ending-letter previews. Furthermore, benefits from beginning letters were greater for words than for pseudowords. Ending-letter previews showed no corresponding lexical superiority. Experiment 3 revealed that preview of position-specific letters from the beginning plus the ending part of target stimuli, which did not reveal a unique word-beginning letter sequence, facilitated the classification of words but not pseudowords. The results support a two-route model of lexical access in which some partial-word previews afford activation of specific lexical representations, and some partial-word previews afford activation of subword representations.

Adult↗
PubMed1999

Medial prefrontal cortex lesions cause deficits in a variable-goal location task but not in object exploration.

The role of the medial prefrontal cortex (PFC) in goal-directed behavior was examined in rats with aspiration lesions. In Experiment 1, PFC lesions resulted in an impaired ability to relearn the location of a behaviorally defined goal arm of a plus-maze after it was moved from an initially fixed position. Lesioned rats also exhibited a significantly greater degree of perseveration compared with control animals. Experiment 2 was an object exploration task in which rats had to respond to a change in the layout of the environment. PFC-lesioned rats performed identically to controls, therefore demonstrating that the deficits observed in Experiment 1 did not result from a deficit in the ability to explore the environment. The results are discussed in terms of several competing, but not mutually exclusive explanations of the role of the PFC in navigation and spatial representation.

Animals↗
PubMed1987

Adult age differences in integrative spatial ability.

Young and older adults were contrasted in three experiments that involved manipulation of the number of required spatial integration operations (Experiments 1 and 2) and manipulation of the amount of information per operation (Experiment 3). Older adults performed at lower levels of accuracy than did young adults in each experiment. However, the magnitude of the age differences tended to increase with each successive integration operation but was constant across different quantities of relevant information. I interpreted these results as suggesting that one factor responsible for age differences in tests of spatial ability is an age-related reduction in the efficiency of executing operations responsible for the accurate and stable representation of spatial information.

Adolescent↗
PubMed2005

Integrating incremental learning and episodic memory models of the hippocampal region.

By integrating previous computational models of corticohippocampal function, the authors develop and test a unified theory of the neural substrates of familiarity, recollection, and classical conditioning. This approach integrates models from 2 traditions of hippocampal modeling, those of episodic memory and incremental learning, by drawing on an earlier mathematical model of conditioning, SOP (A. Wagner, 1981). The model describes how a familiarity signal may arise from parahippocampal cortices, giving a novel explanation for the finding that the neural response to a stimulus in these regions decreases with increasing stimulus familiarity. Recollection is ascribed to the hippocampus proper. It is shown how the properties of episodic representations in the neocortex, parahippocampal gyrus, and hippocampus proper may explain phenomena in classical conditioning. The model reproduces the effects of hippocampal, septal, and broad hippocampal region lesions on contextual modulation of classical conditioning, blocking, learned irrelevance, and latent inhibition.

Hippocampus↗
PubMed1991

Categories and particulars: prototype effects in estimating spatial location.

A model of category effects on reports from memory is presented. The model holds that stimuli are represented at 2 levels of detail: a fine-grain value and a category. When memory is inexact but people must report an exact value, they use estimation processes that combine the remembered stimulus value with category information. The proposed estimation processes include truncation at category boundaries and weighting with a central (prototypic) category value. These processes introduce bias in reporting even when memory is unbiased, but nevertheless may improve overall accuracy (by decreasing the variability of reports). Four experiments are presented in which people report the location of a dot in a circle. Subjects spontaneously impose horizontal and vertical boundaries that divide the circle into quadrants. They misplace dots toward a central (prototypic) location in each quadrant, as predicted by the model. The proposed model has broad implications; notably, it has the potential to explain biases of the sort described in psychophysics (contraction bias and the bias captured by Weber's law) as well as symmetries in similarity judgments, without positing distorted representations of physical scales.

Adolescent↗
PubMed2000

A cortical-hippocampal system for declarative memory.

Recent neurobiological studies have begun to reveal the cognitive and neural coding mechanisms that underlie declarative memory--our ability to recollect everyday events and factual knowledge. These studies indicate that the critical circuitry involves bidirectional connections between the neocortex, the parahippocampal region and the hippocampus. Each of these areas makes a unique contribution to memory processing. Widespread high-order neocortical areas provide dedicated processors for perceptual, motor or cognitive information that is influenced by other components of the system. The parahippocampal region mediates convergence of this information and extends the persistence of neocortical memory representations. The hippocampus encodes the sequences of places and events that compose episodic memories, and links them together through their common elements. Here I describe how these mechanisms work together to create and re-create fully networked representations of previous experiences and knowledge about the world.

Animals↗
PubMed2000

Preschoolers' magnitude comparisons are mediated by a preverbal analog mechanism.

We report a study of 3- to 5-year-olds who performed a magnitude-comparison task. Stimuli were a series of pairs of arrays that sometimes differed in numerosity, and the children were asked to point to the more numerous array in each pair. The proportion of accurate responses was above chance for all age groups. However, error patterns were consistent with analog models of magnitude representation. Errors varied systematically with the ratio of stimulus pairs. Items with a 2:3 ratio were harder than items with a 1:2 ratio. Performance on posttests of verbal counting ability was variable, but did not predict performance on the numerical discrimination task. We argue that neither verbal counting nor nonnumerical perceptual strategies can explain these results. This study supports the hypothesis that adults and children share preverbal, analog representations of magnitude.

Adult↗
PubMed1994

Blocking in Pavlovian conditioning: effect of prior excitatory conditioning to a stimulus extraneous to compound conditioning.

The effect of prior excitatory conditioning to a stimulus not included in the compound conditioning phase of the typical blocking experiment was assessed in three CER studies. The first experiment, in which rat subjects received A+, C+, or a combination of A+/C+ trials prior to AB+ conditioning, showed that A+/C+ or C+ training produced as robust blocking as A+ training relative to a control group with no prior conditioning. A second experiment which was designed to assess the role of background cues in mediating the blocking effect indicated that background cues were not responsible for the A+ or C+ effects, while a third experiment showed these same effects were not mediated by stimulus generalization. The findings of these experiments are interpreted in the context of pseudoconditioning-induced rehearsal of a US representation in short-term memory.

Animals↗