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PubMed2005

Incremental online learning in high dimensions.

Locally weighted projection regression (LWPR) is a new algorithm for incremental nonlinear function approximation in high-dimensional spaces with redundant and irrelevant input dimensions. At its core, it employs nonparametric regression with locally linear models. In order to stay computationally efficient and numerically robust, each local model performs the regression analysis with a small number of univariate regressions in selected directions in input space in the spirit of partial least squares regression. We discuss when and how local learning techniques can successfully work in high-dimensional spaces and review the various techniques for local dimensionality reduction before finally deriving the LWPR algorithm. The properties of LWPR are that it (1) learns rapidly with second-order learning methods based on incremental training, (2) uses statistically sound stochastic leave-one-out cross validation for learning without the need to memorize training data, (3) adjusts its weighting kernels based on only local information in order to minimize the danger of negative interference of incremental learning, (4) has a computational complexity that is linear in the number of inputs, and (5) can deal with a large number of-possibly redundant-inputs, as shown in various empirical evaluations with up to 90 dimensional data sets. For a probabilistic interpretation, predictive variance and confidence intervals are derived. To our knowledge, LWPR is the first truly incremental spatially localized learning method that can successfully and efficiently operate in very high-dimensional spaces.

Algorithms↗

PubMed1992

Taste avoidance, but not aversion, learning in rats lacking gustatory cortex.

Control rats rapidly learned to avoid drinking either a sucrose solution (Experiment 1) or a NaCl solution (Experiment 2) when the taste was paired with illness. These rats also produced aversive reactivity to each of these solutions in a taste reactivity test. Rats that lacked gustatory cortex (GC) learned to avoid drinking sucrose and NaCl, albeit at a slower rate than control rats. GC rats failed to display aversive reactivity to these tastes. The GC rats did show normal aversive reactivity to a strong quinine HCl solution during additional tests. It is suggested that the avoidance developed by GC rats did not entail a palatability shift of the conditional stimulus as it did in control rats. This altered learning strategy may account for the consistent learning deficits found in GC rats trained to avoid tastes.

Animals↗

PubMed2001

Conjunctive representations in learning and memory: principles of cortical and hippocampal function.

The authors present a theoretical framework for understanding the roles of the hippocampus and neocortex in learning and memory. This framework incorporates a theme found in many theories of hippocampal function: that the hippocampus is responsible for developing conjunctive representations binding together stimulus elements into a unitary representation that can later be recalled from partial input cues. This idea is contradicted by the fact that hippocampally lesioned rats can learn nonlinear discrimination problems that require conjunctive representations. The authors' framework accommodates this finding by establishing a principled division of labor, where the cortex is responsible for slow learning that integrates over multiple experiences to extract generalities whereas the hippocampus performs rapid learning of the arbitrary contents of individual experiences. This framework suggests that tasks involving rapid, incidental conjunctive learning are better tests of hippocampal function. The authors implement this framework in a computational neural network model and show that it can account for a wide range of data in animal learning.

Animals↗

PubMedDate not supplied

Operant performance patterns of normal and nervous water-deprived dogs.

Previous studies have shown that most food-deprived genetically nervous pointer dogs fail to learn a bar-pressing response for food reward and those which do learn are erratic in bar-pressing compared to genetically normal pointer dogs which usually learn rapidly and perform well. Benzodiazepine drugs facilitate learning and performance of the responses in nervous dogs. The present study aimed at finding whether a stronger drive producing state, such as water deprivation, would facilitate learning and performance in even severely nervous dogs. Eight normal line and 7 nervous line dogs successfully learned to perform well a paddle-pressing response which activates a valve releasing water into a drinking pan. One disturbing dog of each line did not learn successfully. Behavior shaping was about as easy and as rapid in nervous line dogs as in normals. Nervous line dogs tended to be as consistent in responding. However, response rates of nervous line dogs averaged about two-thirds those of normal line dogs, the slowed rate of responses being taken up mostly in excessive, rather stereotyped, licking of the water pan. Response rates correlated well with degree of nervousness as measured on independent well standardized behavior tests. This behavior seems to add another dimension to the characterization of the nervousness of these "spooky" pointer dogs.

Animals↗

PubMed1996

Orbitofrontal cortex neurons: role in olfactory and visual association learning.

1. The orbitofrontal cortex is implicated in the rapid learning of new associations between visual stimuli and primary reinforcers such as taste. It is also the site of convergence of information from olfactory, gustatory, and visual modalities. To investigate the neuronal mechanisms underlying the formation of odor-taste associations, we made recordings from olfactory neurons in the orbitofrontal cortex during the performance of an olfactory discrimination task and its reversal in macaques. 2. It was found that 68% of odor-responsive neurons modified their responses after the changes in the taste reward associations of the odorants. Full reversal of the neuronal responses was seen in 25% of these neurons. Extinction of the differential neuronal responses after task reversal was seen in 43% of these neurons. 3. For comparison, visually responsive orbitofrontal neurons were tested during reversal of a visual discrimination task. Seventy-one percent of these visual cells showed rapid full reversal of the visual stimulus to which they responded, when the association of the visual with taste was reversed in the reversal task. 4. These demonstrate that of many orbitofrontal cortex olfactory neurons on the taste with which the odor is associated. 5. This modification is likely to be important for setting the motivational value of olfactory for feeding and other rewarded behavior. However, it is less complete, and much slower, than the modifications found or orbit frontal visual during visual-taste reversal. This relative inflexibility of olfactory responses is consistent with the need for some stability is odor-taste associations to facilitate the formation and perception of flavors.

Acoustic Stimulation↗

PubMed1987

Learning and using specific instances.

A biologically plausible method for rapidly learning specific instances is described. It is contrasted with a formal model of classical conditioning (Rescorla-Wagner learning/perception training), which is shown to be relatively good for learning generalizations, but correspondingly poor for learning specific instances. A number of behaviorally relevant applications of specific instance learning are considered. For category learning, various combinations of specific instance learning and generalization are described and analyzed. Two general approaches are considered: the simple inclusion of Specific Instance Detectors (SIDs) as additional features during perception training, and specialized treatment in which SID-based categorization takes precedence over generalization-based categorization. Using the first approach, analysis and empirical results demonstrate a potential problem in representing feature presence and absence in a symmetric fashion when the frequencies of feature presence and absence are very different. However, it is shown that by using the proper representation, the addition of SIDs can only improve the convergence rate of perceptron training, the greatest improvement being achieved when SIDs are preferentially allocated for peripheral positive and negative instances. Some further improvement is possible if SIDs are treated in a specialized manner.

Animals↗

PubMed2005

Rapid word-learning in normal-hearing and hearing-impaired children: effects of age, receptive vocabulary, and high-frequency amplification.

OBJECTIVE: This study examined rapid word-learning in 5- to 14-year-old children with normal and impaired hearing. The effects of age and receptive vocabulary were examined as well as those of high-frequency amplification. Novel words were low-pass filtered at 4 kHz (typical of current amplification devices) and at 9 kHz. It was hypothesized that (1) the children with normal hearing would learn more words than the children with hearing loss, (2) word-learning would increase with age and receptive vocabulary for both groups, and (3) both groups would benefit from a broader frequency bandwidth. DESIGN: Sixty children with normal hearing and 37 children with moderate sensorineural hearing losses participated in this study. Each child viewed a 4-minute animated slideshow containing 8 nonsense words created using the 24 English consonant phonemes (3 consonants per word). Each word was repeated 3 times. Half of the 8 words were low-pass filtered at 4 kHz and half were filtered at 9 kHz. After viewing the story twice, each child was asked to identify the words from among pictures in the slide show. Before testing, a measure of current receptive vocabulary was obtained using the Peabody Picture Vocabulary Test (PPVT-III). RESULTS: The PPVT-III scores of the hearing-impaired children were consistently poorer than those of the normal-hearing children across the age range tested. A similar pattern of results was observed for word-learning in that the performance of the hearing-impaired children was significantly poorer than that of the normal-hearing children. Further analysis of the PPVT and word-learning scores suggested that although word-learning was reduced in the hearing-impaired children, their performance was consistent with their receptive vocabularies. Additionally, no correlation was found between overall performance and the age of identification, age of amplification, or years of amplification in the children with hearing loss. Results also revealed a small increase in performance for both groups in the extended bandwidth condition but the difference was not significant at the traditional p = 0.05 level. CONCLUSIONS: The ability to learn words rapidly appears to be poorer in children with hearing loss over a wide range of ages. These results coincide with the consistently poorer receptive vocabularies for these children. Neither the word-learning or receptive-vocabulary measures were related to the amplification histories of these children. Finally, providing an extended high-frequency bandwidth did not significantly improve rapid word-learning for either group with these stimuli.

Adolescent↗

PubMed1979

Learned suppression of ingestion: role of discriminative stimuli, ingestive responses, and aversive tastes.

Three experiments were designed to demonstrate that animals learn to suppress contact with aversive-tasting foods and fluids, and to investigate the behavioral mechanisms of this learning. In Experiment 1, domestic chicks (Gallus gallus) rapidly learned to suppress drinking during a visual stimulus (SQ) that signaled ingestion of a quinine solution but drank normally during a second visual stimulus (SW) that signaled water access. In Experiment 2, chicks in Group Con received oral infusions of quinine contingent upon drinking during SQ. Group Non received oral quinine infusions during SQ yoked to those of Group Con and noncontingent upon drinking. Only Group Con suppressed drinking during SQ. The third experiment investigated the contribution of the aversive taste and the postingestive effects into either the beak or the crop following drinking during SQ. Only the orally infused subjects suppressed drinking during SQ. These studies suggest that the relation between the drinking response and the aversive taste of quinine during SQ is crucial to the learned suppression of ingestion produced by the present procedures. The implications of these results for theories of food selection and Batesian mimicry are discussed.

Animals↗

PubMed2002

Rapid long lasting learning in a collinear edge-detection task.

We have developed a detection task in which subjects identify a pair of collinear edges in a field of polygons. Five of our six subjects showed significant, rapid learning at this task. Four showed evidence of retention a day and a week later. In several transfer tests, we found that disruption of the distractors produced a significant drop-off in performance. These results are consistent with a model in which collinear targets initially produce a salience signal too weak to be reliably detected over the noise of the distractors. As the experiment proceeds, the visual system learns to dampen the distractor signals, allowing for more reliable detection.

Adult↗

PubMed2001

Rapid, object-based learning in the deployment of transient attention.

We show that transient attention summoned by an exogenous cue shows rapid learning of the relationship between the cue and a subsequent target in a discrimination task. In experiment 1, performance was unaffected when a target always appeared in the same position on a large cue, but was degraded when the target could appear anywhere within the extent of the larger cue. Experiment 2 shows that it was not the predictability of where the target appeared within the cue that aided performance, but rather a consistent location mapping of cue and target, since predictably alternating the target location relative to the cue led to worse performance than when the target was presented in the same location relative to the cue from trial to trial. Further analysis of the results of experiment 2 shows that the learning is rapid, evident after one trial, and has a cumulative influence over four consecutive trials. Possible neural correlates of this form of learning are discussed, with a focus on the supplementary eye fields in the prefrontal cortex. The reported experiments show that transient attention is not a simple reflexive mechanism but can show rapid visuospatial learning, in object-based coordinates.

Association Learning↗

PubMed1993

Laparoscopic management of ectopic pregnancy in a resident training program.

The range of procedures now routinely done through the laparoscope has continued to expand due to improved equipment for insufflation, hemostasis, and tissue manipulation, and to imaginative approaches to otherwise "routine" gynecologic problems traditionally treated by laparotomy. As with all new technologies, advocates predict that the methodology will prove to have an almost unlimited potential, while established skeptics predict that it will have a narrow applicability. With time and further clinical application, a consensus somewhere between the two positions will be reached. But while this technology develops and experience begins to accumulate, it is necessary to train residents in the technique. We discuss our experience with introducing laparoscopic management of ectopic pregnancy into a residency training program. Our results indicate a rapid learning curve, with minimal patient morbidity, brief hospitalization, and rapid convalescence.

Adult↗

PubMed1998

Complementary learning systems in the brain. A connectionist approach to explicit and implicit cognition and memory.

Freud's ideas about the role of non-conscious processes relates to contemporary thinking about explicit and implicit memory, and his early efforts to understand cognition and behavior in terms of neural mechanisms share several themes in common with contemporary connectionist models. The present paper presents a connectionist perspective of the neural basis of learning and memory and their organization in the brain. The central claim of the article is that the neocortex and many other forebrain learning systems learn slowly so as to become sensitive to the overall structure of experience. Slow learning is crucial for sensitivity to this structure and for organizing specific information with other information in a structured way. The hippocampus and related areas in the medial temporal lobes complement these slow learning systems by providing a mechanism that allows the rapid learning of arbitrary conjunctions of elements that go together to make up an episodic memory.

Brain↗

PubMed1977

Learning child psychiatry skills on the adult inpatient service.

Integration of child psychiatry training into general psychiatric residency programs is often unsuccessful. The authors describe an innovative model of training in child psychiatry that involves the children of adult inpatients. This model offers several advantages: splitting of child-adult psychiatric training is avoided, child diagnostic and evaluative skills tend to be learned rapidly, preventive orientations develop, and family process is both learned and used. Preliminary experience with this model on two inpatient services suggests that it is both didactically effective and economical in child psychiatry staff hours.

Adolescent↗

PubMed2002

Learning impairments of hippocampal-lesioned mice in a paddling pool.

Control mice rapidly learned to escape from shallow water in a paddling pool, which combined elements of the Morris water maze and the Barnes holeboard maze. The pool's transparent perimeter wall contained 12 exits, only 1 of which led to an escape tunnel. Learning was impaired in mice with cytotoxic lesions of the hippocampus. Probe trials suggested that the controls were using extramaze cues. When the exit was blocked, controls, but not hippocampals, spent more time searching in this previously correct sector. When the spatial location of the exit was changed, hippocampals escaped more quickly, as they showed no preference for the old location. These results may be useful in the assessment of hippocampal dysfunction, particularly in genetically manipulated mice.

Animals↗

PubMed1976

The effect of delta 9-tetrahydrocannabinol and LSD on the acquisition of an active avoidance response in the rat.

The course of active avoidance learning of rats in a symmetrical Y-maze under the influence of 1, 3, and 9 mg/kg of delta 9-THC i.p., and 5, 20, and mug/kg of LSD was investigated. Delta-THC in a dosage of 1 mg/kg had no effect on avoidance learning. Three to a lesser extent 9 mg/kg produced more rapid learning with a significantly better performance. Learning under delta 9-THC proved to be state-dependent. The withdrawal of delta 9-THC caused a decrease in the avoidance rate, which was dependent on the dosage. Upon renewal of the THC doses, the animals reattained their earlier preformance. In the course of the experiment there was rapid tolerance development, especially of the sedative properties of THC. LSD retarded the rate of acquisition of the active avoidance response. Whereas the control animals displayed over 80% successful active avoidance from the 14th session onwards, this was achieved by the LSD groups only after the 20th session. However, in contrast to the control group the LSD animals were able to increase their avoidance rate to over 90%, and this was maintained to the end of the experiment (a total of 24 sessions with LSD). The sudden withdrawal of LSD produced a fall in avoidance rate, which was dependent on the pervious training dosage; as with delta 9-THC state-dependent learning can also be assumed for LSD.

Animals↗

PubMed2006

The effects of variation on learning word order rules by adults with and without language-based learning disabilities.

UNLABELLED: Non-adjacent dependencies characterize numerous features of English syntax, including certain verb tense structures and subject-verb agreement. This study utilized an artificial language paradigm to examine the contribution of item variability to the learning of these types of dependencies. Adult subjects with and without language-based learning disabilities listened to strings of three non-words for which the first and third elements had a dependent relationship. In the low variability condition, 12 non-words occurred in the middle position, and in the high variability condition, 24 non-words occurred in this position. Non-disabled adults were able to learn the non-adjacent contingencies and generalize the underlying structure to new strings, but only when variability was high. Adults with language-based learning disabilities did not perform above chance levels under either variability condition. Thus, this group showed poor sensitivity to statistical information in speech input that both infants and non-disabled adults are known to track. LEARNING OUTCOMES: As a result of this activity, the reader will: (1) understand the advantages of using an artificial language to investigate language learning; (2) become familiar with a paradigm for studying the rapid learning of syntactic contingencies; (3) comprehend how the ability to map language structure differs for non-disabled adults and adults with a history of language/learning disability as a function of variability in the input the listener receives.

Adolescent↗

PubMed2001

Recognition and categorization of biologically significant objects by rhesus monkeys (Macaca mulatta): the domain of food.

To survive, organisms must be able to identify edible objects. However, we know relatively little about how humans and other species distinguish food items from non-food items. We tested the abilities of semi-free-ranging rhesus monkeys (Macaca mulatta) to learn rapidly that a novel object was edible, and to generalize their learning to other objects, in a spontaneous choice task. Adult monkeys watched as a human experimenter first pretended to eat one of two novel objects and then placed replicas of the objects at widely separated locations. Monkeys selectively approached the object that the experimenter had previously eaten, exhibiting a rapidly induced preference for the apparently edible object. In further experiments in which the same objects were used as tools or were manipulated at the face but not eaten, we fail to observe an approach bias, providing evidence that the monkeys' pattern of approach in the earlier experiments was specific to objects that were eaten. Subsequent experiments tested how monkeys generalized their preference for an edible object by first allowing them to watch a human experimenter eat one of two objects and then presenting them with new objects composed of the same substance but differing from the original, edible object in shape or color. Monkeys ignored changes in the shape of the object and generalized from one edible object to another on the basis of color in conjunction with other substance properties. Finally, we extended this work to infant rhesus monkeys and found that, like adults, they too used color to generalize to novel food objects. In contrast to adults, however, infants extended this pattern of generalization to objects that were acted on in other ways. These results suggest that infant monkeys form broader object categories than adults, and that food categories become sharpened as a function of maturational or experiential factors.

Age Factors↗

PubMed1978

Voice, speech, and language habilitation in young children without laryngeal function.

We discuss aphonia in children, secondary to laryngeal obstruction, with regard to the development of a voice, speech, and language system that can be an effective and efficient means of communication while obstruction persists and a precursor to good voice and speech habits if and when the laryngeal function is reestablished. Several methods were considered. A technique of esophageal voice training for children was developed and implemented, which combined the aspects of normal language learning with the mechanical aspects of esophageal voice production. Results showed rapid learning in a 2 1/2-year-old child with severe juvenile laryngeal papillomatosis and normal speech and language at the age of 4 years when laryngeal function returned. A second technique, a communication board, was used with a 4-year-old child with total subglottic stenosis and brain damage.

Aphonia↗