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At least 487 records · Page 27Linked to original sources

PubMed1993

Induction of combination rules in two-dimensional function learning.

Previous studies have typically found that when people learn to combine two dimensions of a stimulus to select a response, they learn additive combination rules more easily than nonadditive (e.g., multiplicative) ones. The present experiments demonstrate that in some situations people can learn multiplicative rules more easily than other (e.g., additive) rules. Subjects learned to produce specified response durations when presented with stimulus lines varying in length and angle of orientation. When stimuli and correct responses were related by a multiplicative combination of power functions, learning was relatively easy (Experiment 1). In contrast, systematic response biases occurred during the early phases of learning an additive combination of linear functions (Experiment 2) and a more complex (nonadditive and nonmultiplicative) combination of linear functions (Experiment 3), suggesting that people have a tendency to induce a multiplicative combination of power functions. However, the initial biases decreased with practice. These results are explained in terms of a revised adaptive regression model of function learning originally proposed by Koh and Meyer (1991). Differences between the present results and previous results in the literature are discussed.

Adult↗

PubMed2006

Learning in context: linguistic and attentional constraints on children's color term learning.

Three experiments investigated whether linguistic and/or attentional constraints might account for preschoolers' difficulties when learning color terms. Task structure and demands were equated across experiments, and both speed and degree of learning were compared. In Experiment 1, 3-year-olds who were matched on vocabulary score were taught new secondary color terms by corrective, semantic, or referential linguistic contrast. Corrective contrast produced more rapid and more extensive learning than did either semantic or referential contrast, supporting the hypothesis that targeted linguistic feedback facilitates learning. Experiment 2 replicated and extended the first experiment with Italian children and found cross-cultural differences in the amount learned about colors named differently in the two languages. In Experiment 3, some of the children were introduced to the new terms within a context of enhanced perceptual salience. These children learned as fast and performed as accurately as those given corrective linguistic feedback in Experiment 1.

Attention↗

PubMed2005

One-trial visual recognition in cats.

The ability of normal cats to perform delayed matching- and nonmatching-to-sample with trial-unique stimuli was investigated both in a modified Wisconsin General Testing Apparatus requiring manipulatory responses and in a Nencki-type testing room requiring locomotor responses. Cats trained in the WGTA learned the two tasks at about the same rate, on average, as that reported for monkeys. However, unlike monkeys, whose strong preference for novelty facilitates their learning of the nonmatching rule and retards their learning of the matching rule, the cats learned the two different rules at about the same rate, suggesting that cats do not share the monkey's strong preference for novelty. In contrast to their relatively rapid learning of the manipulatory versions of the two tasks, cats learned the locomotor versions only slowly or even failed to learn. Experimental analysis indicated that a major source of the cats' difficulty on these locomotor versions was interference from a strong tendency in the large testing room to use visuospatial strategies. Nevertheless, once the matching or nonmatching rule was learned at short delays, whether in the WGTA or the testing room, the cats performed at criterion levels without further training even at delays of 10 minutes, indicating that this species, like monkeys, has a highly developed long-term recognition memory ability.

Analysis of Variance↗

PubMed1979

Rekitting the Wechsler Paired-Associate Task: the Waterford Index.

The Waterford Index provides a new scoring system for the Wechsler paired-associate task. Item performances across successive trials were coded so as to reflect the psychological phenomena of learning, forgetting and item effects (N = 50). The Index describes two rules for differentiating between cases of cognitive impairment and non-impairment. Rule 1 contrasts the respective contributions of learning and forgetting. Rule 2 takes account of cases characterized by a high proportion of correct responses. Against a criterion index based on performances on other psychological tests of organic dysfunction, the Waterford Index yielded higher predictive efficiencies than associated with other Wechsler indices, intelligence, and age.

Adult↗

PubMed2002

Brain regions controlling nonsynergistic versus synergistic movement of the digits: a functional magnetic resonance imaging study.

Human hand dexterity depends on the ability to move digits independently and to combine these movements in various coordinative patterns. It is well established that the primary motor cortex (M1) is important for skillful digit actions but less is known about the role played by the nonprimary motor centers. Here we use functional magnetic resonance imaging to examine the hypothesis that nonprimary motor areas and the posterior parietal cortex are strongly activated when healthy humans move the right digits in a skillful coordination pattern involving relatively independent digit movements. A task in which flexion of the thumb is accompanied by extension of the fingers and vice versa, i.e., a learned "nonsynergistic" coordination pattern, is contrasted with a task in which all digits flex and extend simultaneously in an innate synergistic coordination pattern (opening and closing the fist). The motor output is the same in the two conditions. Thus, the difference when contrasting the nonsynergistic and synergistic tasks represents the requirement to fractionate the movements of the thumb and fingers and to combine these movements in a learned coordinative pattern. The supplementary (and cingulate) motor area, the bilateral dorsal premotor area, the bilateral lateral cerebellum, the bilateral cortices of the postcentral sulcus, and the left intraparietal cortex showed stronger activity when the subjects made the nonsynergistic flexion-extension movements of the digits than when the synergistic movements were made. These results suggest that the human neural substrate for skillful digit movement includes a sensorimotor network of nonprimary frontoparietal areas and the cerebellum that, in conjunction with M1, control the movements of the digits.

Adult↗

PubMed1996

Successive negative contrast in one-way avoidance: effect of thiopental sodium and chlorpromazine.

The successive negative contrast effect on one-way avoidance was induced by shifting rats from a large reward (30 s spent in the safe compartment after completion of the avoidance response, pre-shift phase) to a small reward (1 s, post-shift phase). Under these conditions, the previously learned avoidance response deteriorated (negative contrast) when compared to a control group for which 'safe time' remained constant throughout the experimental situation (1 s). Thiopental sodium at a dose of 5 or 10 mg/kg, but not at 1, 2, 15 or 20 mg/kg i.p., abolished the negative contrast effect, and did not affect performance of the one-way avoidance task. Similar results were found when rats were treated with diazepam (1 mg/kg i.p.). Chlorpromazine at a dose of 0.5 or 1 mg/kg i.p. did not affect negative contrast, although at higher doses (2 or 3 mg/kg) there was an increase in the number of trials needed to reach the criterion for learning the avoidance response. This increase was evident in both pre-shift and post-shift phases, although only in the experimental situations involving a low level of reinforcement (1 s in the safe compartment). On the basis of these results, we tentatively suggest that the successive negative contrast effect in one-way avoidance in rats can be considered a useful pharmacological animal model for research into anxiety.

Animals↗

PubMed1979

Linguistic experience and phonemic perception in infancy: a crosslinguistic study.

English- and Spanish-learning infants were tested for perception of 2 synthetic speech contrasts differing in voice onset time. The 2 pairs were chosen so that they were native to either Spanish or English. Using the Visually Reinforced Infant Speech Discrimination (VRISD) paradigm, 6--8-month-old infants were taught to respond to a change in auditory stimuli with a headturn. Correct headturns were reinforced by the activation of a lighted animated toy. While Spanish-learning infants provided evidence of discriminating both English and Spanish contrasts, English-learning infants only provided evidence of discriminating their native contrast. The results are discussed in terms of the role of linguistic experience in the development of speech perception skills in infancy.

Cross-Cultural Comparison↗

PubMed2002

Summation in autoshaping is affected by the similarity of the visual stimuli to the stimulation they replace.

Pigeons received autoshaping with 2 stimuli, A and B, presented in adjacent regions on a television screen. Conditioning with each stimulus was therefore accompanied by stimulation that was displaced from the screen whenever the other stimulus was presented. Test trials with AB revealed stronger responding if this displaced stimulation was similar to, rather than different from, A and B. For a further experiment the training just described included trials with A and B accompanied by an additional, similar, stimulus. Responding during test trials with AB was stronger if the additional trials signaled the presence rather than the absence of food. The results are explained with a configural theory of conditioning.

Animals↗

PubMed1987

Motor learning: nonspecific subcortical mechanisms in rats.

Adult rats with bilateral lesions in the globus pallidus, substantia nigra, median raphe, midbrain central gray, or pontine reticular formation were tested for novel motor skill learning (sliding a barrel bolt to the right in order to open a door leading to a reward). Significantly impaired learning was found in animals with lesions to globus pallidus, substantia nigra, median raphe, or pontine reticular formation. These results combined with earlier findings suggest that the foregoing subcortical structures along with the regions of the ventrolateral and parafascicular nuclei of the thalamus constitute a nonspecific mechanism involved not only in motor learning but in discrimination and maze learning as well. This mechanism is contrasted with the more fashionable specific mechanisms which are involved in particular classes of learning; the sensorimotor cortex, for example, would be a component of the specific mechanism underlying motor learning. A subcortical nonspecific learning mechanism may also inhabit the human brain, as suggested by the clinical condition of "subcortical dementia."

Animals↗

PubMedDate not supplied

Increased responsiveness of hippocampal pyramidal neurons to nicotine in aged, learning-impaired rats.

The effect of aging upon the responsiveness of hippocampal CA1 pyramidal neurons to nicotine was investigated using electrophysiological techniques in male Fischer 344 rats. Prior to electrophysiological recording, animals were behaviorally tested using the Morris water maze. All 3-6 and 18-21 month rats displayed rapid place learning in this task, while none of the 27-30 month animals learned within the 5-day test period. By contrast, rats of all age groups were able to learn a cue version of the water maze task. Following behavioral testing, the animals were anesthetized with sodium pentobarbital for acute recording. Nicotine was locally applied to electrophysiologically identified CA1 pyramidal neurons using pressure microejection from two-barreled glass microelectrodes. For each neuron, a dose of nicotine was found which elicited a 300-400% increase in basal firing rate. These data were used to construct cumulative dose response curves for populations of neurons tested in 3-6-, 18-21-, and 27-30-month-old animals. An age-related increase in the responsiveness of CA1 pyramidal neurons to locally applied nicotine was observed. The results of this study suggest that an increase in hippocampal CA1 pyramidal cell responsiveness to nicotine could be related to the impaired place learning ability seen with aging.

Action Potentials↗

PubMed2005

Generalization of frequency discrimination learning across frequencies and ears: implications for underlying neural mechanisms in humans.

Frequency discrimination thresholds (FDTs) at 750, 1500, 3000, and 6000 Hz were measured in 32 normal-hearing listeners before and after each listener practiced the task for 12 h at one of the above frequencies using a single ear. Marked improvements in thresholds taking place over several hours were observed during the frequency- and ear-specific training period. Comparisons between pre- and posttraining thresholds showed large improvements at the trained frequency, but also at other frequencies. The improvements were initially slightly-but significantly-larger at the trained frequency than at untrained frequencies. However, this trained-frequency advantage disappeared rapidly during the course of the two-hour multifrequency posttraining session, suggesting rapid relearning or learning generalization across frequencies. In contrast, no significant ear specificity was found, not even at early stages of the posttraining session. These findings add to earlier results suggesting that, in humans, frequency discrimination learning is only weakly frequency-specific, and they reveal that a complete generalization across frequencies can occur rapidly with little retraining at the initially untrained frequencies. Implications regarding underlying mechanisms are discussed.

Adult↗

PubMed2004

The morbidity and mortality conference: a case assessment tool, quality control measure, and teaching method.

The morbidity and mortality conference and other traditions in hospital-based training inculcate the habits of understanding evidence and its clinical application and being able to articulate these to one's peers and to learn from unanticipated outcomes. By contrast, predoctoral dental training and the environment of general dental practice do not encourage collegial reflection on the outcomes of practice. Benefits and cautions in applying the habits learned through M&M conferences are discussed for both the oral and maxillofacial and the general practice settings.

Education, Dental↗

PubMed2004

Circadian modulation of sequence learning under high and low sleep pressure conditions.

Humans are able to learn complex sequences even without conscious awareness. We have studied the repercussions of circadian phase and sleep pressure on the ability to learn structured sequences using a serial reaction time task (SRT). Sixteen young healthy volunteers were studied in a 40-h "constant posture protocol" under high sleep pressure (i.e. sleep deprivation) and low sleep pressure conditions (i.e. sleep satiation attained by multiple naps). Here we show that learning of different sequence structures improved after multiple naps, in particular after naps that followed the circadian peak of rapid-eye-movement (REM) sleep. This situation following sleep contrasted with the lack of learning without sleep. We have evidenced that the observed amelioration of learning new sequences came about by memorizing short sub-fragments ("chunks") of the sequence train. However, SRT performance did not deteriorate under high sleep pressure, despite the high level of sleepiness. Our data indicate that sequence learning is modulated by circadian phase, and the neurophysiological medium required for this type of learning is related to sleep.

Adult↗

PubMed2006

Roles of octopaminergic and dopaminergic neurons in mediating reward and punishment signals in insect visual learning.

Insects, like vertebrates, have considerable ability to associate visual, olfactory or other sensory signals with reward or punishment. Previous studies in crickets, honey bees and fruit-flies have suggested that octopamine (OA, invertebrate counterpart of noradrenaline) and dopamine (DA) mediate various kinds of reward and punishment signals in olfactory learning. However, whether the roles of OA and DA in mediating positive and negative reinforcing signals can be generalized to learning of sensory signals other than odors remained unknown. Here we first established a visual learning paradigm in which to associate a visual pattern with water reward or saline punishment for crickets and found that memory after aversive conditioning decayed much faster than that after appetitive conditioning. Then, we pharmacologically studied the roles of OA and DA in appetitive and aversive forms of visual learning. Crickets injected with epinastine or mianserin, OA receptor antagonists, into the hemolymph exhibited a complete impairment of appetitive learning to associate a visual pattern with water reward, but aversive learning with saline punishment was unaffected. By contrast, fluphenazine, chlorpromazine or spiperone, DA receptor antagonists, completely impaired aversive learning without affecting appetitive learning. The results demonstrate that OA and DA participate in reward and punishment conditioning in visual learning. This finding, together with results of previous studies on the roles of OA and DA in olfactory learning, suggests ubiquitous roles of the octopaminergic reward system and dopaminergic punishment system in insect learning.

Animals↗

PubMed1993

An examination of the relations between hippocampal long-term potentiation, kindling, afterdischarge, and place learning in the water maze.

Two approaches were used to study the relations between the acquisition of place learning in the Morris water maze and long-term potentiation (LTP), kindling, and afterdischarge (AD). In the first, the possibility of behavioral LTP in the dentate gyrus field potential evoked by stimulation of the perforant path was evaluated in rats that showed robust place learning in the water maze. There was no effect of place learning on the field potential, and field potential measures did not correlate with place learning acquisition measures. In the second approach, the effect of bilateral saturation of LTP on subsequent place learning in the water maze task, begun within 5 minutes of the last LTP session, was evaluated. The effect of kindled seizures evoked bilaterally from the perforant path, or of a single unilateral AD, on acquisition of the water maze task (begun within 10 minutes) were also evaluated. Bilateral LTP saturation did not affect place learning, and the bilateral LTP group learned as readily as controls. In contrast, the kindled and AD groups were severely impaired in their performance of the place learning task. A second day of training in the water maze without any further electrical stimulation indicated that these groups had acquired considerable information on the first day of maze training and were not distinguishable from controls on the second day of training. This indicated that the deficit in these groups on the first day of training was temporary and likely resulted from a temporary perturbation of normal brain function due to the seizures. The results indicate that bilateral saturation of LTP in the dentate gyrus does not affect place learning in the water maze. They also indicate that recent hippocampal seizures, but not kindling, disrupt place learning in this task.

Animals↗

PubMed2002

Hippocampus lesions impair landmark array spatial learning in homing pigeons: a laboratory study.

Hippocampal (HF)-lesioned pigeons display impaired homing ability when flying over familiar terrain, where they are presumably relying on a map-like representation of familiar landmarks to navigate. However, research carried out in the field precludes a direct test of whether hippocampal lesions compromise the ability of homing pigeons to navigate by familiar landmarks. To examine more thoroughly the relationship between hippocampus and landmark spatial learning, control, neostriatum-lesioned, and HF-lesioned homing pigeons were trained on two open field, laboratory, conditional discrimination tasks. One was a visual landmark array task, and the other was a room color discrimination task. For the tasks, the correct of three differently colored food bowls was determined by the spatial relationship among a group of five landmarks and room color, respectively. Intact control birds successfully learned both tasks, while neostriatum-lesioned birds successfully learned the landmark array task-the only task on which they were trained. By contrast, HF-lesioned birds successfully learned the room color task but were unable to learn the landmark array task. The data support the hypothesis that homing performance deficits observed in the field following hippocampal lesions are in part a consequence of an impairment in the ability of lesioned pigeons to use familiar visual landmarks for navigation.

Animals↗

PubMed1992

Impaired learning and memory in mature spontaneously hypertensive rats.

In very old, normotensive rats, a disorganization occurs selectively in the retrosplenial cortex, and a similar disorganization occurs in this area in spontaneously hypertensive rats (SHR) at a much earlier age. Since this breakdown compromises a neural circuit involved in learning and memory, this study tests the hypotheses that these functions are disturbed in mature SHR and that they can be prevented or attenuated by long-term, anti-hypertensive therapy. SHR and Sprague Dawley rats (SD) at 3- and 12 months of age, and a group of SHR that had been normotensive from 3 to 12 months of age (CAP-SHR) were trained on an 8 arm radial maze task. Of the 12-month-old groups, SD reached criterion earliest (28 +/- 2 days) and made the least number of total errors. In comparison, 12-month-old SHR took significantly longer to reach criterion (39 +/- 2 days) and made nearly twice as many total errors. CAP-SHR were intermediate between the other two groups (32 +/- 2 days). Three-month-old SD learned the task at the same rate as the 12-month-old SD. In contrast, 3-month-old SHR learned the task significantly faster (21 +/- 1 days) and with fewer errors than any other group. These data indicate that, in SHR, learning and memory are compromised by 12 months of age, and that anti-hypertensive therapy with captopril partially prevents this decline.

Animals↗

PubMed1989

Maximal opposition approach to phonological treatment.

The purpose of this paper was to evaluate a phonological treatment program of maximal rather than minimal feature contrasts by charting the course of learning in a child displaying a systematic error pattern involving the nonoccurrence of word-initial consonants. Generalization data indicated that the child learned 16 word-initial consonants following treatment of only three sets of maximal opposition contrasts. Overgeneralization data indicated that the child restructured his phonological system based on a larger concept of "word initialness." Basic components of and differences between various forms of contrast treatment are discussed.

Articulation Disorders↗