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At least 451 records · Page 25Linked to original sources
PubMed2005

Spatio-temporal activation of cyclic AMP response element-binding protein, activity-regulated cytoskeletal-associated protein and brain-derived nerve growth factor: a mechanism for pontine-wave generator activation-dependent two-way active-avoidance memory processing in the rat.

The present study explored possible physiological and molecular mechanisms of pontine-wave (P-wave) generator activation-dependent memory processing in the rat using a two-way active-avoidance learning paradigm. The results show that learning training increased rapid eye movement sleep and activated brainstem cells in the P-wave generator. During this period, there was a time-dependent increase in phosphorylation of cAMP response element-binding protein (CREB) in the dorsal hippocampus and amygdala and increased synthesis of activity-regulated cytoskeletal-associated protein (Arc) in the dorsal hippocampus, amygdala, frontal cortex and occipital cortex. Learning training also increased synthesis of brain-derived nerve growth factor (BDNF) in the occipital cortex, amygdala and dorsal hippocampus at different time intervals. During this time, the levels of nerve growth factor did not change. The results also show that the increase in rapid eye movement sleep P-wave density during the post-training 3-h recording session is positively correlated with the increased levels of phosphorylated CREB, BDNF and Arc in the dorsal hippocampus. These results suggest that memory processing of two-way active-avoidance learning may involve excitation of P-wave-generating cells in the brainstem and increased expression of phosphorylated CREB, Arc and BDNF in a time-dependent manner in the forebrain. These dynamic changes in cellular and molecular features provide considerable insight into the mechanisms of the P-wave generator activation-dependent memory consolidation process.

Amygdala↗
PubMed1981

One-trial associative learning modifies food odor preferences of a terrestrial mollusc.

We present evidence of rapid and reliable associative learning by the terrestrial mollusc, Limax maximus. Slugs were exposed once to a pairing of a highly attractive food odor (potato or carrot) and a saturated solution of quinidine sulfate, a bitter-tasting plant substance. In comparison with control slugs, the exposed slugs subsequently displayed a markedly reduced preference for the odor paired with quinidine. This reduced odor preference was limited to the specific odor paired with quinidine and did not generalize to other food odors.

Journal Article↗
PubMed1998

Contextual quick-learning and generalization by humans and machines.

In a previous study (1994 Network: Comput. Neural Syst. 5 203-27) we compared human quick-learning and generalization (quick modelling) with that of neural nets (feedforward architectures), symbolic algorithms (decision tree procedures), and pattern classifiers (truth-set descriptors). Those studies raised the question of the role of context in the nature and rapidity of human learning. Here we address that issue in the setting of the same basic experiment (Quinlan classification problem) used for the previous studies. A major implication of our findings is that humans overwhelmingly seek, create, or imagine context in order to provide meaning when presented with abstract or apparently incomplete or contradictory or otherwise untenable situations.

Adolescent↗
PubMed2004

Learning modifies subsequent induction of long-term potentiation-like and long-term depression-like plasticity in human motor cortex.

Learning may alter rapidly the output organization of adult motor cortex. It is a long-held hypothesis that modification of synaptic strength along cortical horizontal connections through long-term potentiation (LTP) and long-term depression (LTD) forms one important mechanism for learning-induced cortical plasticity. Strong evidence in favor of this hypothesis was provided for rat primary motor cortex (M1) by showing that motor learning reduced subsequent LTP but increased LTD. Whether a similar relationship exists in humans is unknown. Here, we induced LTP-like and LTD-like plasticity in the intact human M1 by an established paired associative stimulation (PAS) protocol. PAS consisted of 200 pairs of electrical stimulation of the right median nerve, followed by focal transcranial magnetic stimulation of the hand area of the left M1 at an interval equaling the individual N20 latency of the median nerve somatosensory-evoked cortical potential (PAS(N20)) or N20-5 msec (PAS(N20-5)). PAS(N20) induced reproducibly a LTP-like long-lasting (>30 min) increase in motor-evoked potentials from the left M1 to a thumb abductor muscle of the right hand, whereas PAS(N20-5) induced a LTD-like decrease. Repeated fastest possible thumb abduction movements resulted in learning, defined by an increase in maximum peak acceleration of the practiced movements, and prevented subsequent PAS(N20)-induced LTP-like plasticity but enhanced subsequent PAS(N20-5)-induced LTD-like plasticity. The same number of repeated slow thumb abduction movements did not result in learning and had no effects on PAS-induced plasticity. Findings support the view that learning in human M1 occurs through LTP-like mechanisms.

Adult↗
PubMed1999

Contributions of tutor and bird's own song experience to neural selectivity in the songbird anterior forebrain.

Auditory neurons of the anterior forebrain (AF) of zebra finches become selective for song during song learning. In adults, these neurons respond more to the bird's own song (BOS) than to the songs of other zebra finches (conspecifics) or BOS played in reverse. In contrast, AF neurons from young birds (30 d) respond equally well to all song stimuli. AF selectivity develops rapidly during song learning, appearing in 60-d-old birds. At this age, many neurons also respond equally well to BOS and tutor song. These similar neural responses to BOS and tutor song might reflect contributions from both song experiences to selectivity, because auditory experiences of both BOS and tutor song are essential for normal song learning. Alternatively, they may simply result from acoustic similarities between BOS and tutor song. Understanding which experience shapes selectivity could elucidate the function of song-selective AF neurons. To minimize acoustic similarity between BOS and tutor song, we induced juvenile birds to produce abnormal song by denervating the syrinx, the avian vocal organ, before song onset. We recorded single neurons extracellularly in the AF at 60 d, after birds had had substantial experience of both the abnormal BOS (tsBOS) and tutor song. Some neurons preferred the unique tsBOS over the tutor song, clearly indicating a role for BOS experience in shaping neural selectivity. In addition, a sizable proportion of neurons responded equally well to tsBOS and tutor song, despite their acoustic dissimilarity. These neurons were not simply immature, because they were selective for tsBOS and tutor song relative to conspecific and reverse song. Furthermore, their similar responses to tsBOS and tutor song could not be attributed to residual acoustic similarities between the two stimuli, as measured by several song analyses. The neural sensitivity to two very different songs suggests that single AF neurons may be shaped by both BOS and tutor song experience.

Acoustic Stimulation↗
PubMed1992

Eyeblink conditioning in the developing rat.

Long-Evans rat pups, 17-18 or 24 days of age, were trained with an eyeblink conditioning (EBC) procedure that was used previously with adult rats (Skelton, 1988). Pups received 3 sessions of delay conditioning in a single day at about 4-hr intervals (100 trials/session). Trials involved pairings of an auditory conditioned stimulus (2.8-kHz, 82-dB tone) and a periocular-shock unconditioned stimulus (US; 100 ms, 2 mA), which were presented 280 ms apart. EBC was observed at both ages, but older pups learned much more rapidly. Subsequent experiments established that this effect is associative (Experiment 2), that age differences in EBC cannot be attributed to differences in ability to respond or in sensitivity to the US (Experiment 3), and that EBC rate can be modulated by motivational state (Experiment 4). This preparation may help elucidate the relation between neural development and the ontogeny of learning.

Aging↗
PubMedDate not supplied

Rapid, labile, and protein synthesis-independent short-term memory in conditioned taste aversion.

Short-term memory is a rapid, labile, and protein-synthesis-independent phase of memory. The existence of short-term memory in conditioned taste aversion (CTA) learning has not been demonstrated formally. To determine the earliest time at which a CTA is expressed, we measured intraoral intake of sucrose at 15 min, 1 hr, 6 hr, or 48 h after contingent pairing of an intraoral infusion of 5% sucrose (6.6 ml over 6 min) and toxic lithium chloride injection (76 mg/kg). Rats were implanted with intraoral catheters to allow presentation of taste solutions at arbitrary times. Intraoral intake was measured under conditions of long-delay, single-trial learning typical of CTA. Rats decreased intraoral intake of sucrose at 15 min after contingent pairing of sucrose and LiCl, but not after noncontingent LiCl or sucrose. Thus CTA learning can be expressed rapidly. To determine if short-term CTA memory is labile and decays in the absence of long-term memory, we measured intraoral intake of sucrose after pairing sucrose with low doses of LiCl. Rats received an intraoral infusion of 5% sucrose (6 ml/6 min); 30 min later LiCl was injected at three different doses (19, 38, or 76 mg/kg). A second intraoral infusion of sucrose was administered 15 min, 1 hr, 3 hr, 4.5 hr, 6 hr, or 48 hr later. The formation of long-term CTA memory was dependent on the dose of LiCl paired with sucrose during acquisition. Low doses of LiCl induced a CTA that decayed within 6 hr after pairing. Central administration of the protein synthesis inhibitor cycloheximide prior to LiCl injection blocked long-term CTA expression at 6 and 48 hr, but not short-term CTA expression at 1 hr. Thus, short-term memory for CTA learning exists that is acquired rapidly and independent of protein synthesis, but labile in the absence of long-term memory formation.

Animals↗
PubMed2003

Prediction precedes control in motor learning.

Skilled motor behavior relies on the brain learning both to control the body and predict the consequences of this control. Prediction turns motor commands into expected sensory consequences, whereas control turns desired consequences into motor commands. To capture this symmetry, the neural processes underlying prediction and control are termed the forward and inverse internal models, respectively. Here, we investigate how these two fundamental processes are related during motor learning. We used an object manipulation task in which subjects learned to move a hand-held object with novel dynamic properties along a prescribed path. We independently and simultaneously measured subjects' ability to control their actions and to predict their consequences. We found different time courses for predictor and controller learning, with prediction being learned far more rapidly than control. In early stages of manipulating the object, subjects could predict the consequences of their actions, as measured by the grip force they used to grasp the object, but could not generate appropriate actions for control, as measured by their hand trajectory. As predicted by several recent theoretical models of sensorimotor control, our results indicate that people can learn to predict the consequences of their actions before they can learn to control their actions.

Biophysical Phenomena↗
PubMed2002

Validation and learning in the Procedicus KSA virtual reality surgical simulator.

BACKGROUND: Advanced simulator training within medicine is a rapidly growing field. Virtual reality simulators are being introduced as cost-saving educational tools, which also lead to increased patient safety. METHODS: Fifteen medical students were included in the study. For 10 medical students performance was monitored, before and after 1 h of training, in two endoscopic simulators (the Procedicus KSA with haptic feedback and anatomical graphics and the established MIST simulator without this haptic feedback and graphics). Five medical students performed 50 tests in the Procedicus KSA in order to analyze learning curves. One of these five medical students performed multiple training sessions during 2 weeks and performed more than 300 tests. RESULTS: There was a significant improvement after 1 h of training regarding time, movement economy, and total score. The results in the two simulators were highly correlated. CONCLUSION: Our results show that the use of surgical simulators as a pedagogical tool in medical student training is encouraging. It shows rapid learning curves and our suggestion is to introduce endoscopic simulator training in undergraduate medical education during the course in surgery when motivation is high and before the development of "negative stereotypes" and incorrect practices.

Computer Simulation↗
PubMed2006

Basal forebrain amnesia: a case study.

OBJECTIVE: To provide new evidence of the existence of basal forebrain amnesia, as a different entity from hippocampal or diencephalic amnesia. BACKGROUND: Some authors consider that the characteristics of amnesia do not depend on lesion site, although others claim there are neuropsychologic differences between amnesias due to hippocampal, diencephalic, and basal forebrain lesions. As to the latter, literature is scarce and controversial. The opportunity to thoroughly study J.S., a man with a high IQ and amnesia, enabled us to reinforce the second hypothesis. METHODS: J.S. is a 47-year-old man who underwent surgery for a pituitary adenoma, the resulting lesion involving only the basal forebrain. We gave him a complete neuropsychologic battery for amnesia and executive functions. RESULTS: J.S. showed severe amnesia with a flat learning curve, a rapid forgetting rate and good recognition, a temporal gradient of several years for remote memory, preserved semantic and procedural memory. Most of the tests for executive functions were normal, although he did have a significant personality change after surgery. CONCLUSIONS: This patient is different from patients with hippocampal or diencephalic lesions, and is similar to other patients reported with basal forebrain lesions. The main difference is the relation between his flat learning curve and preserved recognition, both for visual and verbal material.

Adenoma↗
PubMed1991

GABAA receptor modulation of memory: the role of endogenous benzodiazepines.

GABAA receptors are known to downregulate memory consolidation processes: picrotoxin and bicuculline enhance memory, and benzodiazepines and muscimol depress it. The discovery of naturally occurring benzodiazepines in the brain prompted a recent investigation of whether these compounds could act as physiological regulators of the GABAA receptors involved in memory modulation. Different forms of learning cause a rapid reduction of benzodiazepine-like immunoreactivity in septum, amygdala and hippocampus; microinjection of the benzodiazepine antagonist flumazenil into these regions, at the time that consolidation is taking place, enhances memory. Ivan Izquierdo and Jorge Medina suggest that these and other findings indicate that benzodiazepines released in the septum, amygdala and hippocampus do indeed physiologically downregulate memory storage processes; moreover, benzodiazepine release could be modulated by the anxiety and/or stress associated with each type of learning.

Animals↗
PubMed1975

Imagery as an aid to retrieval for Korsakoff patients.

Six Korsakoff patients and six alcoholic controls learned a five item P-A task under each of the following three learning conditions; Rote, Imagery, and Cued learning. Under all conditions the Korsakoff patients took more trials to learn than did the control patients. However, both imagery learning and cued learning were easier than rote learning for the Korsakoff patients when recall was used as the learning index. When a recognition measure was used instead of the recall, imagery learning proved easiest with no difference existing between cued and rote learning. In a second experiment, the patients were given the cue (a mediating link) during presentation, but not during retrieval. Under this condition the Korsakoff patients learned no more rapidly than they did by rote regardless which response measure was required. It was concluded that imagery can aid both storage and retrieval of verbal information for Korsakoff patients, while cuing aids only the retrieval process.

Alcohol Amnestic Disorder↗
PubMedDate not supplied

Neural correlates of person recognition.

Rapidly identifying known individuals is an essential skill in human society. To elucidate the neural basis of this skill, we monitored brain activity while experimental participants demonstrated their ability to recognize people on the basis of viewing their faces. Each participant first memorized the faces of 20 individuals who were not known to the participants in advance. Each face was presented along with a voice simulating the individual speaking their name and a biographical fact. Following this learning procedure, the associated verbal information could be recalled accurately in response to each face. These learned faces were subsequently viewed together with new faces in a memory task. Subjects made a yes-no recognition decision in response to each face while also covertly retrieving the person-specific information associated with each learned face. Brain activity that accompanied this retrieval of person-specific information was contrasted to that when new faces were processed. Functional magnetic resonance imaging in 10 participants showed that several brain regions were activated during blocks of learned faces, including left hippocampus, left middle temporal gyrus, left insula, and bilateral cerebellum. Recordings of event-related brain potentials in 10 other participants tracked the time course of face processing and showed that learned faces engaged neural activity responsible for person recognition 300-600 msec after face onset. Collectively, these results suggest that the visual input of a recently learned face can rapidly trigger retrieval of associated person-specific information through reactivation of distributed cortical networks linked via hippocampal connections.

Adult↗
PubMedDate not supplied

An age-related spatial learning deficit: choline uptake distinguishes "impaired" and "unimpaired" rats.

A functional decline in the hippocampal formation may underlie the emergence of spatial learning deficits in aged rodents. In this study, sodium-dependent high-affinity choline uptake (HACU) was used to monitor hippocampal function in response to training on a spatial task. The subjects were male Long-Evans rats at either 4 months or 22-24 months of age. Animals were trained to locate a camouflaged escape platform in the Morris water maze. Each animal that received place training had a yoked counterpart that was exposed to swimming in the maze but was not required to learn the task. Animals, both young and aged, were sacrificed after attaining a criterion performance. Relative to animals in the yoked condition, place training significantly reduced HACU in both the young rats and in a subpopulation of the aged animals that learned the task rapidly. In contrast, for aged rats that had an impaired rate of acquisition, no effect of place training on HACU was observed. These results provide evidence for a relationship between the behavioral capacities of aged rats and changes in the status of hippocampal function.

Aging↗
PubMed1974

Quality of stimuli and prefrontal lesions effects on reversal learning in go-no go avoidance reflex differentiation in cats.

Go – no go avoidance reflex differentiation of two acoustic stimuli has been previously established in cats. Then the signalling properties of the conditioned stimuli were reversed and the course of acquisition of a new go-no go differentiation was studied in normal cats and in cats with prefrontal lesions. The hypothesis based on stimulus intensity dynamism theory was: (i) in normal cats acquisition of the new differentiation would be easier if the more effective stimulus of the pair were used as the positive stimulus, and (ii) in prefrontal cats this effect of stimulus quality would be l a or absent. Results confirmed both predictions. The differences in rapidity of reversal learning were almost exclusively due to differences in responding to the new positive stimulus. Prefrontal cats were not deficient in comparison with normal cabs in their inhibitory abilities in spite of the fact that extinction of bar-pressing to the new negative conditioned stimulus was much slower than trader of the avoidance response to the new positive stimulus. At the beginning of reversal learning two opposite changes in responding on no-go trials were observed: (i) a decrease in the number of long-latency responses, which reflected the changed signalling value of the previously positive stimulus, and (ii) an increase in the number of short-latency responses, which was positively correlated with the increase in rate of intertrial responding. The increases in number of short-latency responses to the new negative stimulus and in rate of intertrial responding observed at the beginning of reversal learning were smaller in prefrontal than in normal cabs. Results of the experiment indicate that the "drive disinhibition hypothesis" does not account for the effects of prefrontal lesions on avoidance behavior.

Animals↗
PubMed1974

Olfactory learning-set formation in rats.

Rats trained on 16 two-odor discrimination problems showed rapid acquisition of a learning set and one-trial learning by the end of the problem series. Learning to sample odor cues before responding and adoption of a "win-stay, lose-shift" strategy probably accounts for the virtually errorless learning. Learning-set performance of rats trained with odor stimulus comparable to that reported for primates trained on visual cues.

Animals↗