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PubMed2006

Dynamics of hippocampal and cortical activation during consolidation of a nonspatial memory.

Observations of temporally graded retrograde amnesia after hippocampal damage suggest that the hippocampal region plays a critical, time-limited role in memory consolidation. However, these observations do not indicate where permanent memory is stored, nor do they clarify whether the hippocampus normally remains involved in a nonessential way. Evidence from multiple neural imaging studies indicate the time-limited role of the hippocampus and suggest that the anterior cingulate cortex is a critical storage site of different types of long-term memory. However, each of the previous studies examined spatial memory, leaving open the question of whether different cortical areas support long-term memory for other types of material. We characterized the course of involvement of cortical and hippocampal areas in animals trained in an explicitly nonspatial task. First, we confirmed previous findings that hippocampal damage produces temporally graded retrograde amnesia for the social transmission of a food preference (STFP) within our experimental protocol. Damage to the hippocampal region 1 d, but not 21 d, after training impaired subsequent recall of STFP. Then, we characterized the anatomical patterns of activation of the immediate early gene c-fos during retrieval of STFP immediately and 1, 2, and 21 d after training. The ventral subiculum was activated during retrieval shortly after learning, but the level of activation declined at successive times. In contrast, olfactory recipient regions including piriform, entorhinal, and orbitofrontal cortex showed the opposite pattern, increasingly greater activation in successively later retrieval tests. These findings support the view that different cortical networks support long-term memory for different types of information.

Analysis of Variance↗

PubMedDate not supplied

Role of operative flexible choledochoscopy in calculous biliary tract disease.

BACKGROUND: In India, no study is available regarding the use of operative choledochoscopy in the management of choledocholithiasis. ERCP facilities are not always available at many centres and usually require the expertise of a medical gastroenterologist. In contrast, operative choledochoscopy is a simpler procedure that can easily be learned and practised by many surgeons at the time of CBD exploration. AIMS: To study the role of the flexible choledochoscopy in the diagnosis and management of calculous biliary tract disorders. METHODS: Twenty four patients with choledocholithiasis underwent flexible choledochoscopy. Stones were removed either with Desjardin's forceps or by choledochoscopic instrumentation. Postoperative T-tube cholangiography was done to detect any retained stones. RESULTS: Flexible choledochoscopy was performed in a total of 24 patients. Choledochoscopy was done through a choledochotomy in 23 and through the cystic duct in one patient. The choledochoscope was used following conventional CBD exploration in 18 of the 23 patients. Complete clearance of stones was confirmed by choledochoscopy in 12 of the 18 patients and additional stones were seen in the remaining 6 patients. Fogarty balloon catheter and Dormia forceps were used to extract these stones. A CBD stricture was seen in 4 of these 18 patients and choledochoscopic biopsy was done in one of them. In 5 of the 23 patients, the choedochoscope was used as the initial exploring instrument. Impacted CBD stones were detected in 3 of the 5 patients, external compression of the CBD due to periampullary carcinoma in one and stones in both the ampulla and common hepatic duct in the last patient. Postoperative T-tube cholangiography was done in 10 patients and did not reveal any retained stones. Drainage procedures were carried out in 13 patients: 11 had choledochoduodenostomy and 2 had transduodenal sphincteroplasty. Choledochoscopy was a direct aid in choosing the operative procedure in 21 patients. CONCLUSIONS: Flexible choledochoscopy is the most effective method of CBD exploration and is essential in all patients with choledocholithiasis. No additional morbidity or mortality is caused by this procedure.

Endoscopy↗

PubMed1996

Blockade of NMDA receptors during song model exposure impairs song development in juvenile zebra finches.

Juvenile zebra finches (Poephila guttata) learn their courtship song by memorizing and then reproducing the song of an adult male. Several brain regions involved in song behavior contain N-methyl-D-aspartate (NMDA) receptors, and within one brain nucleus necessary for normal song development, the density of these receptors is twice as high in juveniles that are learning song then in adults that can no longer modify their songs. To determine whether NMDA receptor activation is necessary for normal song development, juvenile zebra finches were systemically injected with the NMDA receptor antagonist MK-801 (0.1 mg/kg) before exposure to an adult male tutor. One control group received the same number of MK-801 injections 24 h out of phase with tutoring, and another received saline before tutoring. In adulthood, birds given MK-801 before tutoring showed little evidence of learning from the tutor, and their songs contained abnormal syllables typical of untutored birds. In contrast, all control birds developed normal songs and copied an average of 72.5% of the tutor's syllables. Acute injections of MK-801 did not alter auditory brainstem evoked potentials in juveniles, indicating that the behavioral effects of MK-801 on song learning were not due to temporary hearing loss. Our results suggest that normal song development in juvenile zebra finches requires NMDA receptor activation during song model presentation.

Animals↗

PubMed1999

The importance of monitoring and self-regulation during multitrial learning.

Theory suggests that accuracy of metacognitive monitoring and self-regulation of study will affect test performance, but there is little empirical evidence linking these variables. I examined the relation among these variables in a multitrial learning task. Regression analyses showed that monitoring accuracy and self-regulation were reliably related to test performance--greater monitoring accuracy and more effective self-regulation were associated with greater test performance. These analyses were contrasted with analyses typically conducted in previous research, to show the importance of using a multitrial learning task and of attending to the theoretically based causal relation among variables when evaluating how monitoring accuracy and self-regulation are related to test performance. The results of this investigation may help to explain why previous research has failed to link these variables.

Achievement↗

PubMed1996

Evidence for extrahippocampal involvement in place learning and hippocampal involvement in path integration.

Although there is a good deal of evidence that animals require the hippocampus for learning place responses, animals with damage to the afferent and efferent fibers coursing through the fimbria-fornix have been shown to acquire a place response. This finding suggests either that the cells of the hippocampus proper (CA1-4 and dentate gyrus), via their connections to the temporal lobe, can mediate place learning or that some extrahippocampal structure is sufficient. We examined this question using rats with ibotenic acid lesions of the cells of the hippocampus. Rats were pretrained to swim to a visible platform and then given probe trials on which the visible platform was removed. Video and kinematic analyses showed that the hippocampal rats expected to find the platform at its previous location because they swam directly to that location and paused and turned at that location after the platform was removed. Additional tests confirmed that they had learned a place response. There were, however, abnormalities in their swimming patterns, and despite having acquired one place response, they did not then acquire new place responses when only the hidden platform training procedure was used. These results demonstrate that place learning can be acquired by rats in which the hippocampus proper is removed. Contrasts between conditions in which hippocampal rats acquire a place response and conditions in which they fail suggests that the hippocampus may serve as an on line system for monitoring movement and integrating movement paths.

Animals↗

PubMed2004

Tool-use learning in Tonkean macaques (Macaca tonkeana).

The transmission of tool use is a rare event in monkeys. Such an event arose in a group of semi-free-ranging Tonkean macaques (Macaca tonkeana) in which leaning a pole against the park's fence (branch leaning) appeared and spread to several males. This prompted us to test individual and social learning of this behavior in seven young males. In the first experiment, three males learned individually to obtain a food reward using a wooden pole as a climbing tool. They began using the pole to retrieve the reward only when they could alternatively experience acting on the object and reaching the target. In a second experiment, we first tested whether four other subjects could learn branch leaning after having observed a group-mate performing the task. Despite repeated opportunities to observe the demonstrator, they did not learn to use the pole as a tool. Hence we exposed the latter subjects to individual learning trials and they succeeded in the task. Tool use was not transmitted in the experimental situation, which contrasts with observations in the park. We can conclude that the subjects were not able to recognize the target as such. It is possible that they recognized it and learned the task individually when we alternated the opportunity to act upon the object and to reach the reward. This suggests that these macaques could then have associated the action they exercised upon the pole and the use of the pole as a means to reach the reward.

Animals↗

PubMed1999

Applied psychophysiology and learned physiological regulation.

This commentary emphasizes the importance of including animal research and basic human research, contrasts the present state of affairs for biofeedback in the United States versus Europe, and proposes an alternative, more expanded definition of applied psychophysiology, which includes research, diagnostics, and education, as well as interventions.

Animals↗

PubMed1993

Modeling mortality in the intensive care unit: comparing the performance of a back-propagation, associative-learning neural network with multivariate logistic regression.

The objective of this study was to compare and contrast two techniques of modeling mortality in a 30 bed multi-disciplinary ICU; neural networks and logistic regression. Fifteen physiological variables were recorded on day 3 for 422 consecutive patients whose duration of stay was over 72 hours. Two separate models were built using each technique. First, logistic and neural network models were constructed on the complete 422 patient dataset and discrimination was compared. Second, the database was randomly divided into a 284 patient developmental dataset and a 138 patient validation dataset. The developmental dataset was used to construct logistic and neural net models and the predictive power of these models was verified on the validation dataset. On the complete dataset, the neural network clearly outperformed the logistic model (sensitivity and specificity of 1 and .997 vs. .525 and .966, area under ROC curve .9993 vs. .9259), while both performed equally well on the validation dataset (area under ROC of .82). The excellent performance of the neural net on the complete dataset reveals that the problem is classifiable. Since our dataset only contained 40 mortality events, it is highly likely that the validation dataset was not representative of the developmental dataset, which led to a decreased predictive performance by both the neural net and the logistic regression models. Theoretically, given an extensive dataset, the neural network should be able to perform mortality prediction with a sensitivity and a specificity approaching 95%. Clinically, this would be an extremely important achievement.(ABSTRACT TRUNCATED AT 250 WORDS)

Hospital Mortality↗

PubMed2000

A learning rule for dynamic recruitment and decorrelation.

The interest in neuronal networks originates for a good part in the option not to construct, but to train them. The mechanisms governing synaptic modifications during such training are assumed to depend on signals locally available at the synapses. In contrast, the performance of a network is suitably measured on a global scale. Here we propose a learning rule that addresses this conflict. It is inspired by recent physiological experiments and exploits the interaction of inhibitory input and backpropagating action potentials in pyramidal neurons. This mechanism makes information on the global scale available as a local signal. As a result, several desirable features can be combined: the learning rule allows fast synaptic modifications approaching one-shot learning. Nevertheless, it leads to stable representations during ongoing learning. Furthermore, the response properties of the neurons are not globally correlated, but cover the whole stimulus space.

Animals↗

PubMed2005

Implicit learning of ignored visual context.

Humans process a visual display more efficiently when they encounter it for a second time, showing learning of the display. This study tests whether implicit learning of complex visual contexts depends on attention. Subjects searched for a white target among black and white distractors. When the locations of the target and the attended set (white distractors) were repeated, search speed was enhanced, but when the locations of the target and the ignored set (black distractors) were repeated, search speed was unaffected. This suggests that the expression of learning depends on attention. However, during the transfer test, when the previously ignored set now was attended, it immediately facilitated performance. In contrast, when the previously attended set now was ignored, it no longer enhanced search speed. We conclude that the expression of visual implicit learning depends on attention but that latent learning of repeated information does not.

Adolescent↗

PubMed2001

Educating nurses to care for the dying in Hong Kong: a problem-based learning approach.

Caring for dying patients is an essential and major aspect of nursing care. However, previous studies have revealed that nurses felt uncomfortable and inadequate in dealing with the dying patients and their families. This study reports the effectiveness of a problem-based learning approach in death education among a group of registered nurses in Hong Kong. Three problems, with three segmented scenarios related to cancer nursing, were used. Students went through the problem-based learning process and documented their learning throughout the course in journals. A total of 72 sets of journals were collected and analyzed. The strategies of within case and cross-case analysis were employed. The within case analysis explored the learning development of students for each problem. The cross-case analysis compared and contrasted findings of the within case analysis. Three themes have been derived from the findings. They were: nurses acknowledging their emotions in facing death and dying, a need for the nurses to be better equipped in communication and counseling, and a holistic and family-centered approach to care. This study provides evidence showing that problem-based learning is an effective strategy to enhance nurses' self-awareness of death and dying issues, and to stimulate nurses to formulate a plan that addresses the physical, psychological, and social aspects of care. Findings also reveal that nurses need to take into account the particular reactions of death and dying in the Chinese culture when planning care.

Adult↗

PubMed1999

Training Japanese listeners to identify English /r/ and /l/: long-term retention of learning in perception and production.

Previous work from our laboratories has shown that monolingual Japanese adults who were given intensive high-variability perceptual training improved in both perception and production of English /r/-/l/ minimal pairs. In this study, we extended those findings by investigating the long-term retention of learning in both perception and production of this difficult non-native contrast. Results showed that 3 months after completion of the perceptual training procedure, the Japanese trainees maintained their improved levels of performance of the perceptual identification task. Furthermore, perceptual evaluations by native American English listeners of the Japanese trainees' pretest, posttest, and 3-month follow-up speech productions showed that the trainees retained their long-term improvements in the general quality, identifiability, and overall intelligibility of their English/r/-/l/ word productions. Taken together, the results provide further support for the efficacy of high-variability laboratory speech sound training procedures, and suggest an optimistic outlook for the application of such procedures for a wide range of "special populations."

Adult↗

PubMed1976

Effects of fructose-1,6-diphosphate administration on learning efficiency and time sense of the honey bee, Apis mellifica carnica.

In discrimination experiments honey bees had to decide between two glass dishes, one placed on a black cross, the other 40 cm away on a black square. In spontaneous selections the bees in 70% of all cases chose the black cross. The bees were then trained to search back and forth between the cross and the square until after 5 min sugar-water was given on the black square. Over a total of 5 learning trials, during which multiple decisions had been made by the searching insects, 96% of all choices were in favour of the black square. If 80 mM fructose-1,6-diphosphate (F-1,6-P2) in 1 M glucose had been ingested by the bees 30 min before the first spontaneous choice, learning was facilitated with 83% deciding in favour of the black square at the first trial compared with 46% of the controls (which had been fed on 1 M glucose only). In both groups of bees the same number of flight approches was made to the cross or square as made by the bees searching for 5 min before the reward was given. Thus no change in general activity or harvesting motivation appears to be induced by F-1,6-P2. When F-1,6-P2 had been given at the end of a successful learning series the bees favoured the black square for up to 3 days. In contrast to the controls no new incentive needed to be given during this period. Ingestion of other metabolites proved either ineffective, as in the case of fructose-6-phosphate or 5'-adenosine monophosphate, or, as observed after feeding citrate plus 3-phosphoglycerate, even reduced the performance. To test the effect of F-1,6P2 on the same time sense (circadian rhythm), bees were trained on three successive days to visit a feeding place at a specific time of day. The control bees which ingested only glucose on the evening of the 3rd day returned at their entrained 24-h interval on the 4th day. In contrast, the maximum frequency of appearance of bees fed on F-1,6-P2 was advanced by one hour, with minor appearance peaks at earlier hours of the day.

Animals↗

PubMedDate not supplied

Neocortical involvement in the acquisition and retention of learned alcohol aversions in rats.

In one experiment, rats lacking gustatory neocortex (GN) were compared with control (both normal and control lesion) rats in the acquisition of a learned alcohol aversion. In a second experiment, the effect of GN ablations on preoperatively learned alcohol aversions was examined. Results showed that rats lacking GN both learned and retained alcohol aversions in a normal manner. These same GN rats, however, extinguished the alcohol aversions significantly faster than controls. These results are in contrast to previous data which indicated that the integrity of the GN was necessary for normal acquisition and retention of learned taste aversions. It is suggested that the odor qualities present in the alcohol stimulus account for the relatively normal performance of GN rats.

Alcohol Drinking↗

PubMed2005

Dynamics of learning-induced spine redistribution along dendrites of pyramidal neurons in rats.

We have previously shown that olfactory-discrimination (OD) learning is accompanied by enhanced spine density along proximal apical dendrites of layer II pyramidal neurons in the piriform (olfactory) cortex. Here we studied the temporal dynamics of learning-induced modifications in dendritic spine density throughout the dendritic trees of these neurons. We observed a transient increase in proximal apical spine density after OD learning, suggesting a strengthening of intrinsic excitatory inputs interconnecting neurons within the olfactory cortex. By contrast, the afferent pathway receiving direct input from the olfactory bulb shows spine pruning, suggesting that the connectivity is weakened. The changes in spine density can be attributed to a net change in number of spines, as the morphometric parameters of the dendrites are unaffected by learning. We suggest that spine density changes may represent a mechanism of selective synaptic reorganization required for olfactory learning consolidation.

Animals↗

PubMed1985

Ontogeny of brain nuclei controlling song learning and behavior in zebra finches.

An anatomically discrete system of interconnected brain nuclei controls production of learned song patterns in adult male zebra finches (Poephila guttata). The corresponding nuclei in females, who do not sing, are greatly reduced in volume. Cells in some telencephalic song-control nuclei accumulate androgens, and male nuclei contain a much higher proportion of hormone-concentrating cells than do female nuclei. The main purpose of this experiment was to examine the normal ontogeny of the total volume of various telencephalic nuclei that have been directly or indirectly implicated in song learning and behavior in male zebra finches. In addition, the corresponding nuclei of age-matched females were examined. The major findings were as follows: the volumes of the caudal nucleus of the ventral hyperstriatum (HVc), the robust nucleus of the archistriatum (RA), and area X increased sharply in males between 12 and 53 days of age, whereas brain regions not involved with song control increased much less. Increases in the size of HVc occurred prior to those in RA and area X. Previous studies have shown that males are learning the auditory and motor characteristics of song during this time. In contrast, the volume of the magnocellular nucleus of the anterior neostriatum (MAN) decreased precipitously in males between 25 and 53 days. Measurements of neuron density and soma size demonstrated that this decreased volume is attributable to a loss of greater than 50% of the neurons in MAN. We have previously shown that lesions of MAN during this time completely disrupt song development. The volumes of HVc and RA were smaller in females than in males at all ages studied. Between 12 and 25 days the volumes of female HVc and RA increased less than brain regions not involved with song control. Female HVc and RA decreased slightly in volume between 25 and 53 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1998

Drawing impossible entities: a measure of the imagination in children with autism, children with learning disabilities, and normal 4-year-olds.

Contemporary findings suggest that the imagination of autistic children is not as limited as was once thought. In contrast, Scott and Baron-Cohen (1996) claim that children with autism are unable to draw pictures of impossible entities. An experiment showed that children with autism, children with moderate learning disabilities, and normal 4-year-olds were equally successful at identifying real and impossible pictures and at completing pictures to make them look either real or impossible. The previously reported inability to draw "impossible" pictures is unlikely to reflect an imaginative deficit and may instead result from a misunderstanding of the task or limitations in the executive abilities required to plan and draw an unusual picture for the first time.

Art↗

PubMed1996

Preferential activation of midbrain dopamine neurons by appetitive rather than aversive stimuli.

Midbrain dopamine systems are crucially involved in motivational processes underlying the learning and execution of goal-directed behaviour. Dopamine neurons in monkeys are uniformly activated by unpredicted appetitive stimuli such as food and liquid rewards and conditioned, reward-predicting stimuli. By contrast, fully predicted stimuli are ineffective, and the omission of predicted reward depresses their activity. These characteristics follow associative-learning rules, suggesting that dopamine responses report an error in reward prediction. Accordingly, neural network models are efficiently trained using a dopamine-like reinforcement signal. However, it is unknown whether the responses to environmental stimuli concern specific motivational attributes or reflect more general stimulus salience. To resolve this, we have compared dopamine impulse responses to motivationally opposing appetitive and aversive stimuli. In contrast to appetitive events, primary and conditioned non-noxious aversive stimuli either failed to activate dopamine neurons or, in cases of close resemblance with appetitive stimuli, induced weaker responses than appetitive stimuli. Thus, dopamine neurons preferentially report environmental stimuli with appetitive rather than aversive motivational value.

Animals↗