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Visual statistical learning in infancy: evidence for a domain general learning mechanism.

The rapidity with which infants come to understand language and events in their surroundings has prompted speculation concerning innate knowledge structures that guide language acquisition and object knowledge. Recently, however, evidence has emerged that by 8 months, infants can extract statistical patterns in auditory input that are based on transitional probabilities defining the sequencing of the input's components (Science 274 (1996) 1926). This finding suggests powerful learning mechanisms that are functional in infancy, and raises questions about the domain generality of such mechanisms. We habituated 2-, 5-, and 8-month-old infants to sequences of discrete visual stimuli whose ordering followed a statistically predictable pattern. The infants subsequently viewed the familiar pattern alternating with a novel sequence of identical stimulus components, and exhibited significantly greater interest in the novel sequence at all ages. These results provide support for the likelihood of domain general statistical learning in infancy, and imply that mechanisms designed to detect structure inherent in the environment may play an important role in cognitive development.

Age Factors↗

Posttraining increases in REM sleep intensity implicate REM sleep in memory processing and provide a biological marker of learning potential.

Posttraining rapid eye movement (REM) sleep has been reported to be important for efficient memory consolidation. The present results demonstrate increases in the intensity of REM sleep during the night of sleep following cognitive procedural/implicit task acquisition. These REM increases manifest as increases in total number of rapid eye movements (REMs) and REM densities, whereas the actual time spent in REM sleep did not change. Further, the participants with the higher intelligence (IQ) scores showed superior task acquisition scores as well as larger posttraining increases in number of REMs and REM density. No other sleep state changes were observed. None of the pretraining baseline measures of REM sleep were correlated with either measured IQ or task performance. Posttraining increases in REM sleep intensity implicate REM sleep mechanisms in further off-line memory processing, and provide a biological marker of learning potential.

Adult↗

The integration of knowledge through interactive Computer-Enhanced Learning in medicine.

Rapid advances in Information Technology in recent years have provided powerful computers and software that can be innovatively applied to create powerful pedagogical courseware that go beyond what precursors like the PLATO project could do on the mainframes of yesteryear. This article focusses on the research and development that we have carried out which is applicable to the whole area of education (including medical education). It introduces the elements of hypertext, hypermedia and the pedagogical user interface. It illustrates the principles necessary for the communication of conceptual, functional and structural knowledge. It emphasises the key aspect of mastery of Information Technology necessary for a new dimension in Computer-Enhanced Learning that will be of relevance to the Information Society of the 21st century.

Computer-Assisted Instruction↗

Recruitment learning of boolean functions in sparse random networks.

This work presents a new class of neural network models constrained by biological levels of sparsity and weight-precision, and employing only local weight updates. Concept learning is accomplished through the rapid recruitment of existing network knowledge - complex knowledge being realised as a combination of existing basis concepts. Prior network knowledge is here obtained through the random generation of feedforward networks, with the resulting concept library tailored through distributional bias to suit a particular target class. Learning is exclusively local - through supervised Hebbian and Winnow updates - avoiding the necessity for backpropagation of error and allowing remarkably rapid learning. The approach is demonstrated upon concepts of varying difficulty, culminating in the well-known Monks and LED benchmark problems.

Algorithms↗

Temporal plasticity in the primary auditory cortex induced by operant perceptual learning.

Processing of rapidly successive acoustic stimuli can be markedly improved by sensory training. To investigate the cortical mechanisms underlying such temporal plasticity, we trained rats in a 'sound maze' in which navigation using only auditory cues led to a target location paired with food reward. In this task, the repetition rate of noise pulses increased as the distance between the rat and target location decreased. After training in the sound maze, neurons in the primary auditory cortex (A1) showed greater responses to high-rate noise pulses and stronger phase-locking of responses to the stimuli; they also showed shorter post-stimulation suppression and stronger rebound activation. These improved temporal dynamics transferred to trains of pure-tone pips. Control animals that received identical sound stimulation but were given free access to food showed the same results as naive rats. We conclude that this auditory perceptual learning results in improvements in temporal processing, which may be mediated by enhanced cortical response dynamics.

Acoustic Stimulation↗

EEG-based system for rapid on-off switching without prior learning.

Details are reported of an EEG-based system that permits a person rapidly and reliably to switch on and off electrical devices without prior learning. The system detects and utilises increases in the amplitude of the alpha component of the EEG spectrum that occur when people close their eyes for more than 1 s. In addition to conventional signal-processing elements, the system incorporates a module for suppressing switching at the output of the system when predetermined noise threshold levels (such as those due to sources of EMG) are exceeded. This work indicates that a majority, perhaps in excess of 90%, of the adult population can demonstrate the control necessary to operate an electrical device or appliance using this system. It is indicated that multi-level switching and quasi-continuous control options are feasible with further development of the system. This work has implications for the design of a system that could be used, for example, to assist the infirm or severely physically disabled to effect greater control over their environment.

Adult↗

Learning ability of orphan foals, of normal foals and of their mothers.

The maze learning ability of six pony foals that had been weaned at birth was compared to that of six foals reared normally. The foals' learning ability was also compared to their mothers' learning ability at the same task; the correct turn in a single choice point maze. The maze learning test was conducted when the foals were 6 to 8 mo old and after the mothered foals had been weaned. There was no significant difference between the ability of orphaned (weaned at birth) and mothered foals in their ability to learn to turn left (6 +/- .7 and 5.1 +/- .1 trials, respectively) or to learn the reversal, to turn right (6.7 +/- .6 and 6.2 +/- .6 trials, respectively). The orphan foals spent significantly more time in the maze in their first exposure to it than the mothered foals (184 +/- 42 vs 55 +/- 15 s. Mann Whitney U = 7, P less than .05). The mothers of the foals (n = 11) learned to turn left as rapidly as the foals (5.9 +/- .7 trials), but they were slower to learn to turn right (9.8 +/- 1.4 vs 6.4 +/- .4 trials, Mann Whitney U = 33, P less than .05), indicating that the younger horses learned more rapidly. There was no correlation between the trials to criteria of the mare and those of her foal, but there was a significant negative correlation between rank in trials to criteria and age (r = -65, P less than .05) when data from the mare and foal trials were combined. The dominance hierarchy of the mares was determined using a paired feeding test in which two horses competed for one bucket of feed. Although there was no correlation between rank in the hierarchy and maze learning ability, there was a correlation between body weight and rank in the hierarchy (r = .7, P less than .05). This may indicate either that heavier horses are likely to be dominant or that horses high in dominance gain more weight. Maternal deprivation did not appear to seriously retard learning of a simple maze by foals, although the orphans moved more slowly initially. The lack of maternal influence on learning is also reflected in the lack of correlation between the mare's learning ability and that of her foal. Young horses appear to learn more rapidly than older horses.

Age Factors↗

Activation of phasic pontine-wave generator prevents rapid eye movement sleep deprivation-induced learning impairment in the rat: a mechanism for sleep-dependent plasticity.

Animal and human studies of sleep and learning have demonstrated that training on various tasks increases subsequent rapid eye movement (REM) sleep and phasic pontine-wave (P-wave) activity, followed by improvement in performance on the learned task. It is well documented that REM sleep deprivation after learning trials blocks the expected improvement in performance on subsequent retesting. Our aim was to test whether experimentally induced P-wave generator activation could eliminate the learning impairment produced by post-training REM sleep deprivation. Rats were trained on a two-way active avoidance-learning task. Immediately thereafter, two groups of those rats received a control vehicle (100 nl saline) microinjection and one group received a carbachol (50 ng in 100 nl saline) microinjection into the P-wave generator. The carbachol-injected group and one of the two control saline microinjected groups were selectively deprived of REM sleep during a 6 hr polygraphic recording session. All rats were then tested on the avoidance-learning task. The rats that received both the control saline injection and REM sleep deprivation showed learning deficits compared with the control saline-injected rats that were allowed to sleep normally. In contrast, the rats that received the carbachol microinjection and REM sleep deprivation demonstrated normal learning. These results demonstrate, for the first time, that carbachol-induced activation of the P-wave generator prevents the memory-impairing effects of post-training REM sleep deprivation. This evidence supports our hypothesis that the activation of the P-wave generator during REM sleep deprivation enhances a physiological process of memory, which occurs naturally during post-training REM sleep.

Animals↗

Tyrosine administration prevents hypoxia-induced decrements in learning and memory.

Exposure to hypobaric hypoxia rapidly produces decrements in learning and memory. Tyrosine, a neurotransmitter precursor, has beneficial behavioral effects when administered to animals and humans exposed to various acute stressors. To determine whether tyrosine would protect rats from the adverse effects of hypobaric hypoxia on spatial reference and working memory, it was administered to 27 male Fischer 344 rats tested in the Morris water maze. Rats were tested starting at 2 and 6 h of an 8 h exposure to a simulated altitude of 5950 m (19,500 ft) or sea level. Tyrosine or placebo was administered 1/2 h prior to each testing session (400 mg/kg, IP). Altitude exposure significantly increased working memory escape latency; treatment with tyrosine reversed this decrement. There was no effect of altitude or tyrosine on reference memory. There were also no treatment-related differences in performance when animals were tested the next day at sea level. The beneficial effects of tyrosine on working memory performance may be due to a direct effect of tyrosine on memory, alleviation of a hypoxia-induced retardation of learning, or to other central or peripheral effects of this dietary catecholamine precursor.

Altitude↗

Tracking pattern learning with single-trial event-related potentials.

OBJECTIVE: The main aim was to track the dynamics of pattern-learning using single-trial event-related potentials (ERPs). A new 'learning-oddball' paradigm was employed presenting eight random targets (the 'no-pattern') followed by eight regular targets (the 'pattern'). In total, six repetitions of the 'no-pattern' followed by the 'pattern' were presented. METHODS: We traced the dynamics of learning by measuring responses to 16 (eight random-eight regular) targets. Since this alternation of the 'no-pattern' followed by the 'pattern' was repeated six times, we extracted single-trial responses to all 96 targets to determine if learning occurred more rapidly with each repetition of the 'pattern.' RESULTS: Following random targets, ERPs contained a marked P3-N2 component that decreased to regular targets, whereas a contingent negative variation (CNV) appeared. ERP changes could be best described by sigmoid 'learning' curves. Single-trial analyses showed that learning occurred more rapidly over repetitions and suggested that the CNV developed prior to the decay of the N2-P3 component. CONCLUSIONS: We show a new paradigm-analysis methodology to track learning processes directly from brain signals. SIGNIFICANCE: Single-trial ERPs analyses open a wide range of applications. Tracking the dynamic structure of cognitive functions may prove crucial in the understanding of learning and in the study of different pathologies.

Acoustic Stimulation↗

Connectionist models of recognition memory: constraints imposed by learning and forgetting functions.

Multilayer connectionist models of memory based on the encoder model using the backpropagation learning rule are evaluated. The models are applied to standard recognition memory procedures in which items are studied sequentially and then tested for retention. Sequential learning in these models leads to 2 major problems. First, well-learned information is forgotten rapidly as new information is learned. Second, discrimination between studied items and new items either decreases or is nonmonotonic as a function of learning. To address these problems, manipulations of the network within the multilayer model and several variants of the multilayer model were examined, including a model with prelearned memory and a context model, but none solved the problems. The problems discussed provide limitations on connectionist models applied to human memory and in tasks where information to be learned is not all available during learning.

Attention↗

Rapid modulation of GABA concentration in human sensorimotor cortex during motor learning.

Movement representations within the human primary motor and somatosensory cortices can be altered by motor learning. Decreases in local GABA concentration and its release may facilitate this plasticity. Here we use in vivo magnetic resonance spectroscopy (MRS) to noninvasively measure serial changes in GABA concentration in humans in a brain region including the primary sensorimotor cortex contralateral to the hand used for an isometric motor sequence learning task. Thirty minutes of motor sequence learning reduced the mean GABA concentration within a 2 x 2 x 2-cm3 voxel by almost 20%. This reduction was specific to motor learning: 30 min of similar, movements with an unlearnable, nonrepetitive sequence were not associated with changes in GABA concentration. No significant changes in GABA concentration were found in the primary sensorimotor cortex ipsilateral to the hand used for learning. These changes suggest remarkably rapid, regionally specific short-term presynaptic modulation of GABAergic input that should facilitate motor learning. Although apparently confined to the contralateral hemisphere, the magnitude of changes seen within a large spectroscopic voxel suggests that these changes occur over a wide local neocortical field.

Adult↗

'Word-learning wizardry' at 1;6.

This article explores whether infants are able to learn words as rapidly as has been reported for preschoolers. Sixty-four infants aged 1;6 were taught labels for either two moving images or two still images. Each image-label pair was presented three times, after which comprehension was assessed using an adaptation of the intermodal preferential looking paradigm. Three repetitions of each label were found to be sufficient for learning to occur, fewer than has previously been reported for infants under two years. Moreover, contrary to a previous finding, learning was equally rapid for infants who were taught labels for moving versus still images. The findings indicate that infants in the early stages of acquiring a vocabulary learn new word-referent associations with ease, and that the learning conditions that allow such learning are less restricted that was previously believed.

Child Language↗

Insulin pump therapy and rapid acting insulin: what have we learned?

Approximately 80 years after the discovery and first human use of insulin, we are still striving to replace insulin in a physiological manner. The development of insulin analogues with superior pharmacokinetics has made mimicking of meal and basal insulin requirements by subcutaneous injection more feasible. Administration by continuous subcutaneous insulin infusion (CSII) has provided additional flexibility in meal timing and modifying basal insulin replacement in response to circadian rhythms. Several studies have documented improved glycaemic control with CSII using a rapid-acting analogue such as insulin lispro, compared with regular human insulin. Lower postprandial glucose peaks and improved HbA1c levels were seen with insulin lispro by CSII. In addition, the frequency of hypoglycaemia was significantly reduced and the counter-regulatory hormone responses were maintained. The use of insulin lispro in CSII, compared with regular human insulin, resulted in improved hepatic glucose output in response to glucagon. The potential for problems of hyperglycaemia and ketoacidosis with interruption of insulin delivery by CSII has been studied. One study showed accelerated development of hyperglycaemia and ketosis with insulin lispro compared with regular human insulin while another showed no difference but return to normal glycaemia was faster when insulin lispro was administered. The use of CSII in the US has grown from 6,600 in 1990 to over 100,000 patients currently. With improved insulins, better methods of delivery and advances in glucose monitoring we will continue progress towards physiological insulin replacement and reduce the long-term complications of diabetes.

Diabetes Mellitus, Type 1↗

Intradimensional and extradimensional shifts in spatial learning.

Animals trained on 2 discriminations learn the 2nd rapidly if the relevant stimuli are from the same dimension as the 1st (an intradimensional or ID shift) but slowly if the relevant stimuli for the 2 problems are from different dimensions (an extradimensional or ED shift). Four experiments examined ID and ED shifts in spatial learning. Rats trained on 2 spatial problems learned the 2nd more rapidly than rats whose 1st problem had been nonspatial. But this difference between ID and ED shifts depended on the spatial relationship between rewarded (S+) and unrewarded (S-) alternatives in the 2 spatial problems. The results imply that rats trained on a spatial discrimination do not learn to attend to all spatial landmarks but only to those that serve to differentiate S+ and S-.

Animals↗

Nicotine improves learning and memory in rats: morphological evidence for acetylcholine involvement.

It has been suggested that nicotine improves rapid information processing (learning and memory) tasks. However, it is not clear which aspects of cognition actually underlie these improvements because relatively less attention has been given to nicotinic cholinergic systems compared to muscarinic systems. The authors therefore studied the effects of nicotine on the learning and memory performance by a step-through passive avoidance task. Nicotine (0.4 mg/kg) was administered s.c. single dose (acute group), once a day for 3 days (subchronic group) or 21 days (chronic group). Nicotine treated and control rats were trained in one trial learning step-through passive avoidance task, where retention latencies were carried out 1 h, 24 h, and 3 days after learning trial. Treatment with nicotine before training session prolonged the latencies significantly (p < .01). Control group, acute, subacute and chronic nicotine treatment groups showed latencies 4.75 +/- 0.6, 69.4 +/- 14, 116.2 +/- 30, and 118.5 +/- 23 s, respectively. In addition, to prove the actual contribution of nicotinic cholinergic system in improvement of learning and memory processing, histological methods that permit the visualization and quantification of ACh levels were used. Electron microscopic evaluation revealed increased numbers of Ach-containing vesicles especially in hippocampus in chronic nicotine-treated rats; although frontal and temporal cortex in addition to hippocampus showed increment in Ach vesicles in a lesser extent in all nicotine treatment groups. These results indicate that long-term nicotine treatment can be important for improving cognitive function in regard to increased cholinergic activity.

Acetylcholine↗

Neural net simulation of the corpus callosum.

The effects of simulated anatomical and physiological parameters were investigated in a "neural net" model, where two neural nets corresponding to two small patches of cerebral cortex were connected by a simulated "corpus callosum." The isolated neural nets have previously been shown to exhibit oscillatory activity similar to the raw EEG. By connecting the nets with fibers which have a specified percentage of inhibition and a specified percentage of homotopicity, the effects of such parameters on the cyclic activity of the nets were studied. It was found that, regardless of the inhibitory-excitatory nature of the simulated corpus callosum, the cyclic activity established in one hemisphere is more readily transferred to the contralateral hemisphere, the greater the percentage of homotopic callosal fibers. Learning was more rapid when the effect of the corpus callosum was primarily excitatory, but learning also took place over inhibitory or mixed callosal tracts. The simulation does not therefore resolve the issue of the predominant physiological effect of the corpus callosum, but does indicate that, given the assumptions of the simulation, "learning" can occur regardless of the percentage of excitatory or inhibitory fibers. It is noteworthy that homotopicity was more important for learning across an inhibitory tract than across an excitatory tract.

Animals↗

Learning to cope with biting flies: rapid NMDA-mediated acquisition of conditioned analgesia.

A 30-min exposure to intact biting flies (stable flies) induced an opioid-mediated analgesia in fly-naive male deer mice, whereas exposure to either altered biting flies whose biting mouthparts were removed or nonbiting house flies had no significant effects. However, mice that were previously exposed to intact stable flies for 30 min exhibited significant analgesia when exposed 24-168 hr later to stable flies whose biting parts were removed, but not to nonbiting house flies. Administration of the specific N-methyl-D-aspartate (NMDA) antagonist NPC 12626 to fly-naive mice before exposure to intact flies, although not significantly reducing the analgesic response, blocked the subsequent conditioned analgesia. Naloxone, which blocked the intact biting fly-induced analgesia, did not alter the acquisition of the conditioned analgesic response to the altered stable flies. This demonstrates an NMDA-mediated acquisition of conditioned analgesia to a natural aversive stimulus.

Adaptation, Physiological↗