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PubMed1997

Simultaneous color contrast in goldfish--a quantitative study.

A set of 9-15 colored test fields was presented to goldfish. In Experiment 1, test field hues ranged from green through yellow to red; in Experiment 2, the hues varied from blue through gray to yellow. In the training conditions, the test fields were presented with a gray or black surround. The fish learned to choose one intermediate test field hue by rewarding them with food. In the test conditions, the color of the surround was changed from gray to green, or red (Experiment 1), and from black to blue, or yellow (Experiment 2). The choice behavior of the goldfish changed substantially: one of the test fields other than the training test field was preferred. Direction and strength of simultaneous color contrast was quantified in goldfish color space. The effect of spatial stimulus configuration was investigated by changing test field size and using narrow annular surrounds. With test field radii ranging between 2 and 7.5 mm simultaneous color contrast was optimal whenever the ratio between surround width and test field radius had a value of about 1:1.

Algorithms↗

PubMed2004

Differential enantioselective effects of pentyl-4-yn-valproate on spatial learning in the rat, and neurite outgrowth and cyclin D3 expression in vitro.

Previously, we demonstrated the racemic form of the valproate (VPA) analogue, 2-n-pentyl-4-pentynoic acid ([+/-]pentyl-4-yn-VPA), to be neuritogenic in vitro and to enhance cognition in vivo. To determine the enantioselectivity of these effects, the racemate and purified enantiomers of [+/-]pentyl-4-yn-VPA (84 mg/kg, i.p.) were administered to rodents 20 min prior to multi-session water maze training. The racemate and R-enantiomer significantly reduced escape latencies during water maze learning and enhanced its recall in a probe trial 3 days later. In contrast, S-pentyl-4-yn-VPA did not influence these behavioural parameters. The enantiomer-specific effects of [+/-]pentyl-4-yn-VPA were further discriminated in vitro using neuro 2A neuroblastoma and C6 glioma cell lines. In neuro 2A, the S-enantiomer induced profound neurite outgrowth at concentrations up to 0.5 mm, with the R-enantiomer and racemate being less neuritogenic. Immunoblot analysis of cyclin D3 expression in C6 glioma indicated the racemate and S-pentyl-4-yn-VPA to induce dose-dependent up-regulation of this protein, similar to that associated with G1-phase cell cycle arrest mediated by VPA, whereas R-pentyl-4-yn-VPA was without effect. These results indicate that the cognition-enhancing effects of pentyl-4-yn-VPA are due to the actions of the R-enantiomer, and that cyclin D3 up-regulation and associated anti-proliferative and pro-differentiative actions are predominantly associated with the S-enantiomer.

Animals↗

PubMed2006

Cone contrast computations: physical versus perceived background and colour constancy.

The light reflected from an object depends both on the object's surface and on the illuminant. Visual systems attempt to resolve this intrinsic ambiguity by comparing the light reflected from the object with respect to the background by computing the difference between the object-background light sampled by three cones. The cone-contrasts for the sample-background stimulus under the test illumination should correspond to the cone-contrasts for samples matched in appearance under the standard background (C). The validity of this cone-contrast rule (Whittle, 2003) and its possible link with stability of perceived colour was studied here using six test illuminants. A successive asymmetric colour-matching task with 40 simulated Munsell samples (value 7, chroma 4) on a neutral background (N7) was used. The subject adjusted the sample under standard illuminant C to match the colour appearance of the test sample under one of the test illuminants. Brunswik Ratio (BR) was used as an index of stability of colour appearance. When computed with respect to the reference illuminant C, the cone contrast rule was violated (particularly for S-cone-contrast). However, if a new reference point based on the perceived colour of the neutral background under the test illumination was used, the cone contrast rule applied. That is, when cone contrasts of the matching samples are computed with respect to this perceived background, they correspond to cone contrasts of the test stimuli. This represents a form of discounting the illuminant for the purpose of determining an object's cone-contrast against the background, which does not vary with background illumination. These cone contrasts, however, do not provide any information about the colour appearance of objects under particular viewing conditions, unless calibrated against a standard by allowing subjects to learn particular colours.

Adaptation, Ocular↗

PubMed1995

Importance of learned resourcefulness to weight loss and early success during maintenance: preliminary evidence.

The present study examined the importance of learned resourcefulness skills as measured by Rosenbaum's Self-Control Schedule (SCS) (Behav Ther 1980; 11: 109-121) to weight loss following a self-control program. Twenty-two women signed up for the 5-week self-control program. Participants' weight was recorded at the first and final session of the program, and at a 4-week follow-up. Results indicated that low resourceful women were more likely to drop out of the self-control program than high resourceful women. Although both the high and low resourceful women who completed the program lost the same amount of weight, only the high resourceful subjects continued to lose weight at follow-up. In contrast, the low resourceful women regained lost weight. Results point to the importance of learned resourcefulness for maintenance of weight loss following a self-control weight program.

Adult↗

PubMed2002

[Postgraduate education of neurology (PGEN) in Japan].

PGEN in USA consists of a 3-year well-organized program. This includes 18 months' in-patient service, and 12 months' rotation to various electives, also providing various conferences and lectures. Residents are salaried, so that they are able to concentrate on learning neurology. After completing the residency, the majority of the residents appear to enter their private practice. In contrast, PGEN in Japan does not have a determined period of training, and residents here are not salaried enough, so that they have to do part-time jobs to make their own living. This prevents our residents from concentrating on learning neurology. A rotation system is also difficult to be established in Japan because of the lack of manpower and subspecialists, and tight time schedule partly because of the part-time jobs. Although an affective domain as one of the educational objectives has been ignored in Japan, we should pay more attention to this domain to educate residents to good neurologists. It is also important to encourage staffs to be actively involved in the postgraduate education. In order to do this, we should evaluate their teaching achievements for their promotion appropriately, and senior staffs are required to organize the educational environments.

Education, Medical, Graduate↗

PubMed2003

Transitivity, flexibility, conjunctive representations, and the hippocampus. II. A computational analysis.

A computational neural network model is presented that explains how the hippocampus can contribute to transitive inference performance observed in rats (Dusek and Eichenbaum, 1997. Proc Natl Acad Sci U S A 94:7109-7114; Van Elzakker et al., 2003. Hippocampus 12:this issue). In contrast to existing theories that emphasize the idea that the hippocampus contributes by flexibly relating previously encoded memories, we find that the hippocampus contributes by altering the elemental associative weights of individual stimulus elements during learning. We use this model to account for a range of existing data and to make a number of distinctive predictions that clearly contrast these two views.

Animals↗

PubMed1986

Behavioral functions and hippocampal cell types: evidence for two nonoverlapping populations in the rat.

Extracellular recordings of individual hippocampal neurons in behaving rats were classified by several different electrophysiological criteria as theta (theta-) or complex spike cells. The firing characteristics of each cell were studied in two different behavioral contexts, each of which contained experimental conditions in which firing correlates of these cells have been demonstrated previously. Forty-eight theta-cells and 68 complex spike cells were classified and studied electrophysiologically as animals performed an operant auditory discrimination task or freely explored an open platform environment for water reward. Spontaneous discharge characteristics, as well as electrically evoked firing patterns following stimulation of hippocampal fiber pathways, consistently differentiated theta-cells from complex spike cells. In agreement with previous reports, these results indicate that theta-cells and complex spike cells represent electrophysiologically and possibly morphologically different types of hippocampal neurons. A clear dichotomy also emerged between the firing correlates of identified theta-cells and complex spike cells in the two behavioral tests. During auditory-discrimination learning and performance, time-locked theta-cell discharges to tone onset were correlated with the emergence of conditioned behavioral responding. Increased activity of theta-cells was also observed during locomotion in the spatial exploration task. Time-locked increases in firing to the tone stimulus were restricted to identified theta-cells. Complex spike cells, in contrast to theta-cells, did not increase activity during any phase of tone-discrimination learning or performance. The same cells, however, fired at markedly increased rates coincident with the animals' presence in specific spatial locations during exploration of the platform but did not fire during other overt behaviors on the platform such as grooming, drinking, or locomotion. Complex spike cells qualified on the basis of positive collision tests and antidromic criteria as hippocampal output neurons. "Spatial firing" was unique to complex spike cells and was not observed from theta-cells recorded from the same animal. Twenty-one theta-cells and 31 complex spike cells studied in both behavioral contexts showed mutually exclusive and nonoverlapping electrophysiological firing correlates. No cell was observed in either category which exhibited spatial and tone discrimination related firing correlates.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1978

Maternal speech to normal and Down's syndrome children matched for mean length of utterance.

The study was designed to provide data on the maternal linguistic environments of normal and Down's syndrome children at three levels of language development, as assessed by children's mean length of utterances (MLU). The three MLU levels were 1.00--1.50, 1.75--2.25, and 2.50--3.00, respectively. The subjects were 21 Down's syndrome children and their natural mothers and 21 normal children and their natural mothers. Normal children ranged in chronological age from 20 to 32 months and Down's syndrome children from 3 to 12 years. A one-hour verbal interaction between mother and child was tape recorded at home in a free-play situation. Maternal speech was analyzed using 20 measures related to its output-numerical, lexical, syntactical, semantic-structural, semantic-pragmatic, and language-teaching aspects. Additionally, eight measures of children's speech related to the output-numerical, lexical, syntactical semantic-structural aspects, and to imitativeness of maternal speech were computed as a means of testing the validity of the MLU-matching that forms a basis for this study. Except for the Type-token ratio, which favored Down's syndrome children, normal and Down's syndrome children were not found to differ. In contrast, there were numerous differences between the children in the different aspects of speech considered according to language level. None of the comparisons made of mother's speech to normal and to Down's syndrome children led to differences for any of the three children's language levels studied. It appeared that the maternal linguistic environments of language-learning Down's syndrome and normal children of corresponding MLU were similar in most respects. In contrast, there were numerous differences in mother's speech according to the language level of the children addressed. This confirmed that the expressive language level of the children is a far more powerful factor in influencing maternal speech than whether they are normal or Down's syndrome children. The implications of these findings were related to the delay-difference question in the language development of Down's syndrome children and to various interpretations of the effects of maternal linguistic input for language development and for intervention programs of language enhancement in the Down's syndrome child.

Adult↗

PubMed2007

Reversing the truth effect: learning the interpretation of processing fluency in judgments of truth.

Repeated statements receive higher truth ratings than new statements. Given that repetition leads to greater experienced processing fluency, the author proposes that fluency is used in truth judgments according to its ecological validity. Thus, the truth effect occurs because people learn that fluency and truth tend to be positively correlated. Three experiments tested this notion. Experiment 1 replicated the truth effect by directly manipulating processing fluency; Experiment 2 reversed the effect by manipulating the correlation between fluency and truth in a learning phase. Experiment 3 generalized this reversal by showing a transfer of a negative correlation between perceptual fluency (due to color contrast) and truth to truth judgments when fluency is due to prior exposure (i.e., repetition).

Cues↗

PubMed2005

Induction of cAMP response element-binding protein-dependent medium-term memory by appetitive gustatory reinforcement in Drosophila larvae.

The fruit fly Drosophila melanogaster has been successfully used as a model animal for the study of the genetic and molecular mechanisms of learning and memory. Although most of the Drosophila learning studies have used the adult fly, the relative complexity of its neural network hinders cellular and molecular studies at high resolution. In contrast, the Drosophila larva has a simple brain with uniquely identifiable neural networks, providing an opportunity of an attractive alternative system for elucidation of underlying mechanisms involved in learning and memory. In this paper, we describe a novel paradigm of larval associative learning with a single odor and a positive gustatory reinforcer, sucrose. Mutant analyses have suggested importance of cAMP signaling and potassium channel activities in larval learning as has been demonstrated with the adult fly. Intriguingly, larval memory produced by the appetitive conditioning lasts medium term and depends on both amnesiac and cAMP response element-binding protein (CREB). A significant part of memory was disrupted at very early phase by CREB blockade without affecting immediate learning performance. Moreover, we also show that synaptic output of larval mushroom body neurons is required for retrieval but not for acquisition and retention of the larval memory, including the CREB-dependent component.

Animals↗

PubMed2006

Source memory in the absence of successful cued recall.

Five experiments were conducted to address the question of whether source information could be accessed in the absence of being able to recall an item. The authors used a paired-associate learning paradigm in which cue-target word pairs were studied, and target recall was requested in the presence of the cue. When target recall failed, participants were asked to make a source judgment of whether a man or woman spoke the unrecalled item. In 3 of the 5 experiments, source accuracy was at or very close to chance. By contrast, if cue-target pairs were studied multiple times or participants knew in advance of learning that a predictive judgment would be required, then predictive source accuracy was well above chance. These data are suggestive that context information may not play a very large role in metacognitive judgments such as feeling-of-knowing ratings or putting one into a tip-of-the-tongue state without strong and specific encoding procedures. These same results also highlight the important role that item memory plays in retrieving information about the context in which an item was experienced.

Cues↗

PubMed1991

Effects of short-lasting inactivations of the ventral hippocampus and medial septum on long-term and short-term acquisition of spatial information in rats.

This study was aimed at testing the effects of a reversible inactivation of the hippocampal formation on long-term and short-term acquisition of spatial information. Rats chronically equipped with either bilateral cannulae into the ventral hippocampus or a single cannula into the medial septum had to locate, in a circular platform with 18 holes on the periphery, the unique hole leading to a hidden shelter in order to avoid bright light. In Expt. 1, following 16 days of training (1 trial/day, 24 h ITI) without physical intervention, the location of the correct hole was changed on both Days 17 and 23, and the rats were either sham-injected or injected with lidocaine. Both hippocampally and septally lidocaine-injected rats relearned the new location at a rate similar to corresponding sham-injected animals. In Expt. 2, a massed-trial version of the task was used, in which the rats had to learn a new hole location on each daily session (3 trials, ITI = 1 min). Animals were sham-injected or lidocaine-injected on alternate sessions. While sham-injected rats improved in orientational accuracy over successive trials, both hippocampally and septally lidocaine-injected rats failed to display any between-trial improvement. The impairment displayed by lidocaine-injected rats when their hippocampus was inactivated confirms the role of the hippocampus in short-term spatial memory (Expt. 2). In contrast, short-lasting inactivation of the hippocampus did not prevent long-term spatial learning (Expt. 1). These results suggest that the hippocampus could process information 'off-line' in the delay between temporally discontiguous learning trials, and show that short-term and long-term spatial learning rely on distinct neurobiological mechanisms.

Animals↗

PubMed1997

Shift in the performance of 24-month-old Wistar rats in the Morris water escape task: a comparison across 36 experiments.

Spatial discrimination learning in aged rats serves as an animal model of cognitive aging. We assessed the replicability of spatial discrimination performance in the standard Morris water escape task. To this end the learning curves and the performance in a probe trial of 24-month-old outbred Wistar (HsdWin:Wu) control rats from 36 experiments were compared. These experiments had been performed at our laboratory under strictly controlled conditions over a period of 71 weeks. There was a very high variability in the learning curves between experiments. The initial performance level, i.e. the performance during the first session, did not change systematically across the 36 experiments. In contrast, the final performance level, i.e. the level reached in the fifth training session, decreased over the 71 week period, when the platform escape latency and the distance swam to reach the platform, measured as number of line crossings, were considered. In the last experiments of the series, learning curves were no longer seen: the rats did not improve their performance across the acquisition sessions. By contrast, the swimming speed and, in the probe trial, the bias for the quadrant where the platform had been positioned during training, did not change. This indicates that a decrease across experiments occurred predominantly with respect to spatial orientation performance, whereas the motor performance appeared to be unchanged. Explanations for this observation, such as differences in viability between shipments and the possible occurrence of genetic drift, are discussed.

Aging↗

PubMed1989

Brief communication: a simple model for teaching double-contrast examinations of the gastrointestinal tract.

Good double-contrast studies of the stomach and colon demand a meticulous examination technique. The radiology resident learning this technique often has difficulty understanding the effect of patient positioning on the barium and air. A simple three-dimensional model is described here which helps the resident understand the rationale for the sequence of manoeuvres required to move the barium and air through the gut.

Audiovisual Aids↗

PubMed2006

Learning hierarchically structured action sequences is unaffected by prefrontal-cortex lesion.

This study tested the impact of prefrontal-cortex lesion on learning hierarchically structured action sequences. Using a visual-manual serial reaction time task, we had subjects first perform five blocks of trials with a hierarchically structured 14-element action sequence and then tested for sequence-specific learning by introducing a pseudo-random transfer sequence. Relative to control subjects (N = 39), we found that both lateral frontal (N = 16) and medial frontal (N = 18) patients showed reduced overall performance benefits across the training phase. In contrast, the negative transfer test showed significantly increased reaction times in all patient groups, indicating robust sequence-specific learning. This learning was not significantly different from that of the control group. Taken together, the data suggest that learning hierarchically structured action sequences is unimpaired in patients with prefrontal-cortex lesion.

Adult↗

PubMed1995

The AXR1 and AUX1 genes of Arabidopsis function in separate auxin-response pathways.

The recessive mutations aux1 and axr1 of Arabidopsis confer resistance to the plant hormone auxin. The axr1 mutants display a variety of morphological defects. In contrast, the only morphological defect observed in aux1 mutants is a loss of root gravitropism. To learn more about the function of these genes in auxin response, the expression of the auxin-regulated gene SAUR-AC1 in mutant and wild-type plants has been examined. It has been found that axr1 plants display a pronounced deficiency in auxin-induced accumulation of SAUR-AC1 mRNA in seedlings as well as rosette leaves and mature roots. In contrast, the aux1 mutation has a modest effect on auxin induction of SAUR-AC1. To determine if the AUX1 and AXR1 genes interact to facilitate auxin response, plants which are homozygous for both aux1 and axr1 mutations have been constructed and characterized. The two mutations are additive in their effects on auxin response, suggesting that each mutation confers resistance by a different mechanism. However, the morphology of double mutant plants indicates that there is an inter-action between the AXR1 and AUX1 genes. In mature plants, the aux1-7 mutation acts to partially suppress the morphological defects conferred by the axr1-12 mutation. This suppression is not accompanied by an increase in auxin response, as measured by SAUR-AC1 expression, suggesting that the interaction between the AUX1 and AXR1 genes is indirect.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1994

Hemispheric teaching strategies in the acquisition and retention of a motor skill.

An extreme preference in processing information within either the left or right hemisphere is known as hemisphericity. A previous study investigating hemisphericity as a factor in motor skill learning (Murray, 1979) found that matching subjects' hemisphericity characteristics with hemispherical teaching strategies enhanced skill acquisition. In contrast, our study examined the effects of hemispherical teaching strategies on a group of subjects who did not present hemisphericity. Right-handed male high school students were randomly assigned to either a left hemisphere, right hemisphere, or an interhemispherical teaching condition. Subjects in the right hemisphere and interhemispherical conditions performed and learned the skill more effectively than subjects in the left hemisphere teaching condition. The right hemisphere and interhemispherical groups performed comparably in acquisition; however, the interhemispherical group showed significantly better retention of the skill. Motor skill acquisition and retention for nondominant processors appears best served by directing both verbal and nonverbal attention to the skill.

Adolescent↗

PubMed1996

Adult auditory learning and training.

We describe a theoretical framework that distinguishes stimulus, procedural, and task aspects of learning, and we suggest that this framework may allow an improved understanding of acclimatization and late-onset auditory deprivation. We review the literature on learning after sensorineural hearing loss and after the provision of amplification. We then examine the possibility of using training to improve the speech-understanding skills of listeners with sensorineural hearing loss after provision of amplification. Here, we concentrate on techniques recently demonstrated to encourage the acquisition of non-native phonetic contrasts in second-language learners. We argue that there are three general principles associated with auditory learning and training: 1) the more complex the task, the longer the learning period required; 2) the greater the similarity between training and test tasks, the greater the transfer of training; and 3a) the more familiar the stimulus materials, the faster the subsequent learning. When training for speech identification in everyday life, maximizing the opportunity for the listener to cope with the acoustic variability found in natural speech, both within and between talkers, is important. We, therefore, argue that the third principle should be extended: 3b) the more the training set exemplifies the acoustic variability found within and between talkers, the greater the transfer to open-set speech identification in everyday life. Throughout the review, we show that individual differences in learning are observed in the rate of acquisition and in the level of asymptotic performance. We argue that it is possible to postulate modulators of learning that may account for some of these individual differences. Possible candidates for influential modulators are: 1) the history of hearing impairment--the longer the history, the longer the time taken to improve performance and, possibly, the lower the asymptotic level of performance; 2) the severity and pattern of hearing loss; 3) the degree of asymmetry in the hearing loss and its effect on the binaural organization of the hearing system; and 4) the level of patient adaptability and cognitive abilities, such as attentional control and short-term memory span.

Cognition↗