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PubMed1986

Post-ingestive food-aversion learning to amino acid deficient diets by the terrestrial slug Limax maximus.

An agar-based artificial diet containing carbohydrates, fats and twenty amino acids was constructed. This diet is highly palatable and nutritionally complete for Limax maximus as demonstrated by significant ingestion on first encounter, consistent ingestion on subsequent days and good growth of young slugs fed this diet. Removing methionine, an essential amino acid, from the complete diet produces a food which is initially as palatable as the complete diet, but after one day's intake the amount of this deficient diet eaten is greatly reduced. Removing alanine, a nonessential amino acid, does not produce any decrement in feeding relative to the complete diet. A single meal can be sufficient for establishing the aversion to the deficient diet. Following seven days of feeding on the deficient diet the aversion is retained with little or no attenuation for at least 30 days and does not generalize to either a known 'safe' food or a novel food. Evidence of a mild neophobia towards the artificial diet which attenuated after one or two meals was seen. The learned aversion to the deficient diet is reversible if slugs are repeatedly fed the complete diet following feeding on the deficient diet. Also, slugs initially fed the complete diet will develop an aversion to the methionine-deficient diet after sampling it. Slugs readily ate the artificial diets when these were offered 7 days post-hatch. The methionine-deficient diet however was not eaten in large amounts after the first meals and did not support growth. Baby slugs fed the methionine-deficient diet for 10 days and then maintained on rat chow ate only small amounts when the deficient diet was presented again 126 days later, while baby slugs fed the complete diet or an alanine deficient diet for 10 days ate large amounts when these diets were presented 126 days later. Supplementing the methionine-deficient diet with an injection of methionine into the haemocoel one hour after the completion of a meal completely blocks the development of a learned aversion while injection of Limax saline does not. These results are best explained by the hypothesis that the slugs acquire, post-ingestively, an aversion to the taste and probably the odor of the diet as the result of associative learning.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMedDate not supplied

A language learning model for finite parameter spaces.

This paper shows how to formally characterize language learning in a finite parameter space, for instance, in the principles-and-parameters approach to language, as a Markov structure. New language learning results follow directly; we can explicitly calculate how many positive examples on average ("sample complexity") it will take for a learner to correctly identify a target language with high probability. We show how sample complexity varies with input distributions and learning regimes. In particular we find that the average time to converge under reasonable language input distributions for a simple three-parameter system first described by Gibson and Wexler (1994) is psychologically plausible, in the range of 100-150 positive examples. We further find that a simple random step algorithm-that is, simply jumping from one language hypothesis to another rather than changing one parameter at a time-works faster and always converges to the right target language, in contrast to the single-step, local parameter setting method advocated in some recent work.

Adult↗
PubMed2005

Individual differences in causal learning and decision making.

In judgment and decision making tasks, people tend to neglect the overall frequency of base-rates when they estimate the probability of an event; this is known as the base-rate fallacy. In causal learning, despite people's accuracy at judging causal strength according to one or other normative model (i.e., Power PC, DeltaP), they tend to misperceive base-rate information (e.g., the cause density effect). The present study investigates the relationship between causal learning and decision making by asking whether people weight base-rate information in the same way when estimating causal strength and when making judgments or inferences about the likelihood of an event. The results suggest that people differ according to the weight they place on base-rate information, but the way individuals do this is consistent across causal and decision making tasks. We interpret the results as reflecting a tendency to differentially weight base-rate information which generalizes to a variety of tasks. Additionally, this study provides evidence that causal learning and decision making share some component processes.

Cognition↗
PubMed2002

Teaching Bayesian reasoning: an evaluation of a classroom tutorial for medical students.

How likely is a diagnosis, given a particular medical test result? This probability can be determined by using Bayes's rule; however, previous research has shown that doctors often experience problems with Bayesian inferences. These findings illustrate the need to teach statistical reasoning in medical education. A new method of teaching Bayesian reasoning is representation learning: the key idea is to instruct medical students how to translate probability information into a representation that is easier to process, namely natural frequencies. This approach was implemented in a one-hour classroom tutorial to evaluate its effectiveness in this setting and compared with a traditional rule-learning approach. Evaluation took place two months after training by testing students' ability to correctly solve a Bayesian inference task with information represented as probabilities. While both approaches improved performance, almost three times as many students were able to profit from representation training as opposed to rule training.

Adult↗
PubMed1994

Evaluation of school children at high risk for fragile X syndrome utilizing buccal cell FMR-1 testing.

We describe a pilot project utilizing saliva to identify the FMR-1 mutation in high-risk special education students from four public school districts in Colorado. The program included presentations to special education teachers regarding fragile X syndrome, parental consent for testing, completion of a behavior checklist by the teachers, identification of special education students at high risk for fragile X syndrome, subsequent brief examination of face and hands, collection of a saliva sample by either Gatorade swish or brushing of the inside of the cheek, and analysis for the FMR-1 mutation by PCR. Equivocal samples were studied by direct DNA testing using Southern blot analysis, and abnormal results were confirmed by a blood analysis for the FMR-1 mutation. Mutant individuals received genetic counseling and medical and educational assessments to optimize treatment and intervention. This pilot project was met with enthusiasm by the schools. Of the first 439 students evaluated, 68% were male with an average age of 7.75 years; 13% were mentally retarded or autistic. Most students referred for the evaluation were learning disabled (51%) and/or had an Attention Deficit Hyperactivity Disorder (ADHD) (35%). The overall prevalence of the FMR-1 mutation was 5 of 439 or 1.1%. This relatively low yield is probably due to the high number of non-retarded but learning disabled students tested. Of the mentally retarded patients tested, 3.5% were positive for the FMR-1 mutation; however, of the non-retarded or learning disabled patients, only 0.79% were FMR-1 positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2004

Simple spike and complex spike activity of floccular Purkinje cells during the optokinetic reflex in mice lacking cerebellar long-term depression.

Cerebellar long-term depression (LTD) at parallel fibre-Purkinje cell (P-cell) synapses is thought to embody neuronal information storage for motor learning. Transgenic L7-protein kinase C inhibitor (PKCI) mice in which cerebellar LTD is selectively blocked do indeed exhibit impaired adaptation in the vestibulo-ocular reflex (VOR) while their default oculomotor performance is unaffected. Although supportive, these data do not definitively establish a causal link between memory storage required for motor learning and cerebellar LTD. As the L7-PKCI transgene is probably activated from the early stages of P-cell development, an alternative could be that P-cells develop abnormal signals in L7-PKCI mutants, disturbing mechanisms of motor learning that rely on proper P-cell outputs. To test this alternative hypothesis, we studied simple spike (SS) and complex spike (CS) activity of vertical axis P-cells in the flocculus of L7-PKCI mice and their wild-type littermates during sinusoidal optokinetic stimulation. Both SS and CS discharge dynamics appeared to be very similar in wild-type and transgenic P-cells at all stimulus frequencies (0.05-0.8 Hz). The CS activity of all vertical axis cells increased with contralateral stimulus rotation and lagged ipsiversive eye velocity by 165-180 degrees. The SS modulation was roughly reciprocal to the CS modulation and lagged ipsiversive eye velocity by approximately 15 degrees. The baseline SS and CS discharge characteristics were indistinguishable between the two genotypes. We conclude that the impaired VOR learning in L7-PKCI mutants does not reflect fundamental aberrations of the cerebellar circuitry. The data thus strengthen the evidence that cerebellar LTD is implicated in rapid VOR learning but not in the development of normal default response patterns.

Action Potentials↗
PubMed2004

Protein structure and fold prediction using tree-augmented naive Bayesian classifier.

For determining the structure class and fold class of Protein Structure, computer-based techniques have became essential considering the large volume of the data. Several techniques based on sequence similarity. Neural Networks, SVMs, etc have been applied. This paper presents a framework using the Tree-Augmented Networks (TAN) based on the theory of learning Bayesian networks but with less restrictive assumptions than the naive Bayesian networks. In order to enhance TAN's performance, pre-processing of data is done by feature discretization and post-processing is done by using Mean Probability Voting (MPV) scheme. The advantage of using Bayesian approach over other learning methods is that the network structure is intuitive. In addition, one can read off the TAN structure probabilities to determine the significance of each feature (say, Hydrophobicity) for each class, which help to further understand the mystery of protein structure. Experimental results and comparison with other works over two databases show the effectiveness of our TAN based framework. The idea is implemented as the BAYESPROT web server and it is available at http://www-appn.comp.nus.edu.sg/-bioinfo/bayesprot/Default.htm.

Artificial Intelligence↗
PubMed2005

Protein structure and fold prediction using Tree-Augmented naïve Bayesian classifier.

Due to the large volume of protein sequence data, computational methods to determine the structure class and the fold class of a protein sequence have become essential. Several techniques based on sequence similarity, Neural Networks, Support Vector Machines (SVMs), etc. have been applied. Since most of these classifiers use binary classifiers for multi-classification, there may be (N) c2 classifiers required. This paper presents a framework using the Tree-Augmented Bayesian Networks (TAN) which performs multi-classification based on the theory of learning Bayesian Networks and using improved feature vector representation of (Ding et al., 2001). In order to enhance TAN's performance, pre-processing of data is done by feature discretization and post-processing is done by using Mean Probability Voting (MPV) scheme. The advantage of using Bayesian approach over other learning methods is that the network structure is intuitive. In addition, one can read off the TAN structure probabilities to determine the significance of each feature (say, hydrophobicity) for each class, which helps to further understand the complexity in protein structure. The experiments on the datasets used in three prominent recent works show that our approach is more accurate than other discriminative methods. The framework is implemented on the BAYESPROT web server and it is available at http://www-appn.comp.nus.edu.sg/~bioinfo/bayesprot/Default.htm. More detailed results are also available on the above website.

Algorithms↗
PubMed1994

A comparative study of dynamic and static testing in abstinent alcoholics.

The performance of 44 Finnish alcoholics was measured on a Vygotskian version of the Raven's Progressive Matrices and four traditional static tests (the Digit Symbol and Block Design subtests from the WAIS, Part B of the Trial Making Test, and the Embedded Figures Test). Of the static tests only the Block Design showed consistent congruence with the results of the learning potential test. The other static tests discriminated only partially from each other the groups which were formed according to learning potential. The most fruitful way to test alcoholics is probably to have a flexible combination of static and dynamic tests. We also need to have tests that are applicable to both static and dynamic testing.

Adult↗
PubMed2002

Learning, retention and generalization of a mirror tracing skill in Alzheimer's disease.

The present study examined the ability of 12 patients with probable Alzheimer's disease (AD) and 12 age- and education-matched normal control (NC) subjects to learn and retain the visuomotor skills necessary to efficiently trace a pattern (e.g., a 4- or 6-pointed star) seen only in mirror-reversed view. Those AD (N=6) and NC (N=7) subjects who were able to initially perform the basic mirror tracing task did not differ significantly in initial level of performance, learning over trials, retention of the skill over a 30-min delay interval, and generalization of the skill to a new figure or to the opposite direction of tracing. The AD patients who were unable to initially perform the mirror tracing task were significantly worse than those who could perform the task on several neuropsychological measures sensitive to deficits in problem solving and executive functions, but not on tests of global cognitive decline, memory, language, or visuoperceptual functioning. These results indicate that acquisition and retention of a complex visuomotor skill can proceed normally in the early stages of AD in those individuals who can initially perform the basic task, and that inability to perform the basic task may be related to the frontal lobe dysfunction that is often prominent in the disorder.

Aged↗
PubMed2000

Computers and the Internet: tools for lifelong learning.

Mastery of computer technology and the resources it brings to renal dietitians will be essential for future practice. The Internet, probably the most valuable resource computers bring to clinical practice, is a potential tool to fulfill goals of lifelong learning. A basic introduction to the Internet and a review of search engines and successful search strategies are provided. Major flaws of the Internet include uncertain quality and accuracy of many materials it provides. Guidelines to evaluate World Wide Web (WWW) materials are similar to guidelines dietitians use to assess written materials. The identification of certain anchor WWW sites with reliable information is a key to successful information retrieval on the Internet.

Computers↗
PubMed1989

Learning in mice selectively bred for high and low aggressiveness.

Male mice selectively bred for aggressiveness (TA) and nonaggressiveness (TNA) were compared on maze performance and passive avoidance behavior. The two lines performed the learning tasks in separate ways but the significant differences in performance were probably due to factors other than the brightness of one particular line.

Aggression↗