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Results for “Contrastive learning”

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PubMed1994

A nitric oxide agonist stimulates consolidation of long-term memory in the 1-day-old chick.

Chicks, age 1 to 2 days, that have been trained on a passive avoidance task with a strongly reinforced training trial yield a memory trace that is composed of 3 behaviorally and pharmacologically distinguishable stages, with the final long-term memory stage being dependent on protein synthesis. In contrast, chicks trained with a weakly reinforced learning trial typically do not demonstrate this final stage of memory. Sodium nitroprusside 150 microM intracranially administered immediately after a weak training trial promoted the formation of long-term memory, whereas saline did not. The results suggest that nitric oxide synthesis is either itself critical or stimulates other processes that are critical for the consolidation of long-term memory.

Age Factors↗

PubMed1999

Does awarding a medical degree with honours act as a motivator or demotivator to student learning?

OBJECTIVES: To look at students' support for, and perception of, the effects of awarding a degree with honours. DESIGN: Questionnaires were given to all medical students from those entering year 1 to those graduating, i.e. six cohorts. We performed quantitative and qualitative analyses on the responses. SETTING: University of Manchester. SUBJECTS: Medical students. RESULTS: Of 1618 students, 1290 responded (80%). The majority of students thought that we should have a system to award a degree with honours (968/1290[75%]), but this support was related to a number of variables. When asked to rate their agreement to a series of statements, students from the later years were more likely to disagree that an honours system is a helpful motivator for students to learn (Kruskal-Wallis; P < 0.0001). In contrast, those students with 'points' counting towards an honours degree were more likely to agree that there should be an honours system (chi2[1]=18.7, P < 0.0001). CONCLUSIONS: Most students supported the honours system. However, there was less support from students in later years. The qualitative analysis showed a mixture of views. There was a relationship between the probability of being awarding a degree with honours and support of the system.

Education, Medical, Undergraduate↗

PubMed1997

Some thoughts on the response to antigens that are effector T-helper independent ('thymus independence')

The Self-Non-Self discrimination is germline-selected for defence mechanisms ('innate immune systems') whereas it is somatically learned for immune systems ('adaptive immune systems'). It is proposed that immune system evolved from defence mechanisms by adding large recognitive repertoires that, by aggregating with antigens, were able to trigger the already existent effector functions of defence mechanisms. Thus today there are two pathways to triggering each class of effector function (macrophage opsonization, complement lysis or natural killer/-natural cytotoxic cell activity). The antigen-antibody complex and the T-cell antigen-receptor interaction trigger the immune pathway: the receptors of the defence mechanism trigger the 'alternate' or 'innate' pathway. The evolutionary selection pressure on defence mechanisms was to increase the size of the recognitive repertoire, which in turn, necessitated the emergence of a somatically learned Self-Non-Self discrimination. By contrast with defence mechanisms that are triggered effector T-helper (eTh) independently by polymers (Signal[3]), immune systems can be activated by monomers, a pathway that requires associative recognition of monomer and the reading of two Signals, Signal[1] resulting from the binding of an epitope to the antigen-receptor complex, Signal[2] delivered by an eTh cell. The evolving immune system hijacked part of this eTh-independent pathway (Signal[3]) into which Signal ([1] + [2]) merged. A model of these relationships is proposed.

Animals↗

PubMed1981

Individual recognition and learning of queen odors by worker honeybees.

A honeybee queen is usually attacked if she is placed among the workers of a colony other than her own. This rejection occurs even if environmental sources of odor, such as food, water, and genetic origin of the workers, are kept constant in laboratory conditions. The genetic similarity of queens determines how similar their recognition characteristics are; inbred sister queens were accepted in 35% of exchanges, outbred sister queens in 12%, and nonsister queens in 0%. Carbon dioxide narcosis results in worker honeybees accepting nonnestmate queens. A learning curve is presented, showing the time after narcosis required by workers to learn to recognize a new queen. In contrast, worker transfers result in only a small percentage of the workers being rejected. The reason for the difference between queens and workers may be because of worker and queen recognition cues having different sources.

Journal Article↗

PubMed1977

Acquired drive strength as a joint function of UCS intensity and number of CS-UCS pairings.

The form of the empirical law relating acquired drive strength to UCS intensity and number of CS-UCS pairings was investigated in two experiments using 120 and 30 male albino rats, respectively. Strength of UCS was varied at a broad range of intensities. Controls were introduced to prevent the intrusion of competing crouching responses (R1) on the measurement of response strength (R2). Acquired drive strength was found to be curvilinearly related to UCS intensity and number of CS-UCS pairings during conditioning. The relationship was monotonic and negatively accelerated. Habit strength, or sHr, was found to be jointly determined by UCS intensity (D) and number of CS-UCS pairings during aversive conditioning. These results were contrasted with findings for the instrumental appetitive learning case of Hull's system, where it has been shown that sHr and D are independent and interact in a multiplicative fashion in their effect on performance. An historical review of acquired drive experiments was also presented.

Animals↗

PubMed2004

Non-specific effect of fear conditioning and specific effect of social defeat on social recognition memory performance in female rats.

The so called "emotion learning" literature describes the ability of distressing and aversive unconditioned stimuli to classically condition a learned avoidance response. In order to investigate the impact of experience with noxious stimuli in one conditioning context on learning and memory performance in a separate, non-aversively motivated task, juvenile recognition ability was examined in adult female rats exposed previously to one of two environmental stressors. In particular, experimental adult rats were either socially defeated by exposure to an aggressive conspecific rat or fear conditioned using single or multiple pairings with footshock prior to performance of the social recognition task. Experiment 1 established that repeated exposure to a single juvenile resulted in social memory formation reflected in decreased social investigation from the first to the second exposure. Experiment 2 documented that both single and multiple pairings of an environment with footshock produced robust freezing behavior (90-95% suppression of activity). In addition, fear conditioning produced a non-specific 5-60% increase in social investigation time in both single and multiple-pairing fear conditioned groups which confounded the ability of the social recognition measure to assess effects of fear conditioning on learning and memory performance per se. In contrast, Experiment 3 documented that when social recognition memory performance was impaired to 85% of control levels by imposition of a 2 h delay, exposure to a social defeat stressor reinstated optimal social recognition memory performance. These findings suggest that the after effects of fear conditioning include non-specific alteration of social investigation whereas exposure to conspecific aggression enhances subsequent social recognition memory.

Aggression↗

PubMed1997

Mental navigation along memorized routes activates the hippocampus, precuneus, and insula.

Positron emission tomography was used to investigate the functional anatomy of mental simulation of routes (MSR) in five normal volunteers. Normalized regional cerebral blood flow was measured while subjects mentally navigated between landmarks of a route which had been previously learned by actual navigation. This task was contrasted with both static visual imagery of landmarks (VIL) and silent Rest. MSR appears to be subserved by two distinct networks: a non-specific memory network including the posterior and middle parts of the hippocampal regions, the dorsolateral prefrontal cortex and the posterior cingulum, and a specific mental navigation network, comprising the left precuneus, insula and medial part of the hippocampal regions.

Adult↗

PubMed2000

Ageing with long-standing hearing impairment and deafness.

Until recently, ageing with a long-standing disability had not been a major consideration for governments around the world. Policy and planning for this substantial subgroup had not kept abreast with developments in regard to the growing numbers of older people in general. Consultations held in Australia provided information and recommendations for use by governments and service agencies. The focus was on the viewpoints of consumers. This article reports results for people with long-standing deafness and hearing impairment. It is believed that disadvantages throughout life act to restrict freedom of choice and well-being in old age. Important factors perceived to underlie disadvantage include lifelong restricted access to the opportunities afforded by education and employment and their concomitant effects on the ability to develop the skills, attitudes and knowledge necessary for independence in old age; attitudes of others (including service providers); and the complexity and inflexibility of service systems. However, there are positive aspects. Comparison with published reports about people who acquired hearing loss as a result of the ageing process suggests that people with long-standing disability have learned to live with their situation. In contrast, people whose loss was associated with ageing often report emotional issues and isolation.

Adaptation, Psychological↗

PubMed2002

Adaptive elastic segmentation of brain MRI via shape-model-guided evolutionary programming.

This paper presents a fully automated segmentation method for medical images. The goal is to localize and parameterize a variety of types of structure in these images for subsequent quantitative analysis. We propose a new hybrid strategy that combines a general elastic template matching approach and an evolutionary heuristic. The evolutionary algorithm uses prior statistical information about the shape of the target structure to control the behavior of a number of deformable templates. Each template, modeled in the form of a B-spline, is warped in a potential field which is itself dynamically adapted. Such a hybrid scheme proves to be promising: by maintaining a population of templates, we cover a large domain of the solution space under the global guidance of the evolutionary heuristic, and thoroughly explore interesting areas. We address key issues of automated image segmentation systems. The potential fields are initially designed based on the spatial features of the edges in the input image, and are subjected to spatially adaptive diffusion to guarantee the deformation of the template. This also improves its global consistency and convergence speed. The deformation algorithm can modify the internal structure of the templates to allow a better match. We investigate in detail the preprocessing phase that the images undergo before they can be used more effectively in the iterative elastic matching procedure: a texture classifier, trained via linear discriminant analysis of a learning set, is used to enhance the contrast of the target structure with respect to surrounding tissues. We show how these techniques interact within a statistically driven evolutionary scheme to achieve a better tradeoff between template flexibility and sensitivity to noise and outliers. We focus on understanding the features of template matching that are most beneficial in terms of the achieved match. Examples from simulated and real image data are discussed, with considerations of algorithmic efficiency.

Algorithms↗

PubMedDate not supplied

Health education needs of primigravidae.

Forty-eight primigravidae were interviewed when 3-4 months pregnant about their knowledge of fetal development, awareness of hazards to development and sources of information. Although there was reasonable knowledge about normal fetal development, the women were not generally aware of the repercussions of maternal rubella or rationale for many routine tests at antenatal clinics. Fourteen of the women were smoking and only four of these intended to change during pregnancy. The general practitioner was perceived as a vital source of information, in marked contrast to the midwife. Few women reported learning about child development or care at school, but most used pamphlets or books as a source of information.

Adult↗

PubMed2002

Conservation of spatial memory function in the pallial forebrain of reptiles and ray-finned fishes.

The hippocampus of mammals and birds is critical for spatial memory. Neuroanatomical evidence indicates that the medial cortex (MC) of reptiles and the lateral pallium (LP) of ray-finned fishes could be homologous to the hippocampus of mammals and birds. In this work, we studied the effects of lesions to the MC of turtles and to the LP of goldfish in spatial memory. Lesioned animals were trained in place, and cue maze tasks and crucial probe and transfer tests were performed. In experiment 1, MC-lesioned turtles in the place task failed to locate the goal during trials in which new start positions were used, whereas sham animals navigated directly to the goal independently of start location. In contrast, no deficit was observed in cue learning. In experiment 2, LP lesion produced a dramatic impairment in goldfish trained in the place task, whereas medial and dorsal pallium lesions did not decrease accuracy. In addition, none of these pallial lesions produced deficits in cue learning. These results indicate that lesions to the MC of turtles and to the LP of goldfish, like hippocampal lesions in mammals and birds, selectively impair map-like memory representations of the environmental space. Thus, the forebrain structures of reptiles and teleost fish neuroanatomically equivalent to the mammalian and avian hippocampus also share a central role in spatial cognition. Present results suggest that the presence of a hippocampus-dependent spatial memory system is a primitive feature of the vertebrate forebrain that has been conserved through evolution.

Animals↗

PubMed1993

Relationships among academic, neuropsychological, and intellectual status in subtypes of adults with learning disability.

A study was conducted of 102 adults with learning disability for the purposes of (1) contrasting a rule-based with an empirical method of classification into subtypes based on academic achievement levels in reading and arithmetic; and (2) examining cognitive profiles obtained with the Luria-Nebraska Neuropsychological Battery and the Wechsler Adult Intelligence Scale-Revised (WAIS-R) associated with each of the rule and empirically based subtypes. Both similarities and differences were found between classification methods. Both methods indicated that specific reading disability was associated with the most impaired cognitive profiles of the three subtypes identified. However, they did not agree concerning cognitive profiles of subtypes, characterised by a specific arithmetic deficit or a global deficit. It was found that both the Lurid-Nebraska and WAIS-R profiles distinguished among subtypes more by pattern than by level of performance.

Journal Article↗

PubMed1984

Nonalcoholic cirrhosis associated with neuropsychological dysfunction in the absence of overt evidence of hepatic encephalopathy.

Although much is known about the neuropsychological functioning of cirrhotic individuals with Laennec's (alcohol associated) cirrhosis, little is known about the neuropsychological functioning of individuals with nonalcoholic cirrhosis. In the present investigation, we have determined that individuals suffering from chronic nonalcoholic cirrhosis, despite the absence of clinical signs of hepatic encephalopathy, are impaired on neuropsychological tests that measure visuopractic capacity, visual scanning, and perceptual-motor speed. In contrast, intellectual, language, memory, attentional, motor, and learning abilities are intact. In comparison with a chronically ill control group of patients suffering from Crohn's disease, individuals with advanced nonalcoholic cirrhosis exhibit less emotional disturbance, but are more impaired in their daily activities. These findings indicate that individuals with nonalcoholic cirrhosis, even in the absence of overt clinical signs of encephalopathy, manifest neuropsychological impairments and experience significant disruption in the routines of everyday living.

Adult↗

PubMed1997

Hey! It was just a joke! Understanding propositions and propositional attitudes by normally developing children and children with autism.

Two- and three-year-old children were asked why a speaker named objects falsely. Most produced explanations in terms of the speaker's intention to joke. This implies a sensitivity to two distinct levels in language: the proposition itself and the propositional attitude. Children with learning difficulties showed a similar competence. In contrast, most children with autism failed to explain such false statements in these terms, instead merely describing them as "wrong." This was not simply due to a metalinguistic deficit, as they correctly answered questions about what a speaker had said the object was. These results suggest the normally developing toddler has a remarkable facility in processing propositional attitudes, while children with autism do not; and that such an ability is broadly independent of general intelligence.

Adolescent↗

PubMed1992

Defining experiential learning: nurse tutors' perceptions.

Experiential learning and experiential learning methods have been widely discussed in the nursing education literature. This paper offers some of the findings from a study into nurse tutors' and student nurses' perceptions of experiential learning. In the part of the study described here, 12 nurse tutors were interviewed in depth about the way that they defined experiential learning and experiential learning methods. In this paper, those definitions are compared and contrasted with definitions in the literature and implications for nurse education are identified.

Humans↗

PubMed2003

Evaluation of extended training for general practice in Northern Ireland: qualitative study.

OBJECTIVE: To evaluate participants' perceptions of the impact on them of an additional six months' training beyond the standard 12 month general practice vocational training scheme. DESIGN: Qualitative study using focus groups. SETTING: General practice vocational training in Northern Ireland. PARTICIPANTS: 13 general practitioner registrars, six of whom participated in the additional six months' training, and four trainers involved in the additional six months' training. MAIN OUTCOME MEASURES: : Participants' views about their experiences in 18 month and 12 month courses. RESULTS: Participants reported that the 12 month course was generally positive but was too pressurised and focused on examinations, and also that it had a negative impact on self care. The nature of the learning and assessment was reported to have left participants feeling averse to further continuing education and lacking in confidence. In contrast, the extended six month component was reported to have restimulated learning by focusing more on patient care and promoting self directed learning. It developed confidence, promoted teamwork, and gave experience of two practice contexts, and was reported as valuable by both ex-registrars and trainers. However, both the 12 and 18 month courses left participants feeling underprepared for practice management and self care. CONCLUSIONS: 12 months' training in general practice does not provide doctors with the necessary competencies and confidence to enter independent practice. The extended period was reported to promote greater professional development, critical evaluation skills, and orientation to lifelong learning but does not fill all the gaps.

Attitude of Health Personnel↗

PubMed1994

Early ventriculoperitoneal shunt--effects on learning ability and synaptogenesis of the brain in congenitally hydrocephalic HTX rats.

The learning ability of congenitally hydrocephalic HTX rats in which hydrocephalus had been arrested by the insertion of a V-P shunt 7 days after birth (early shunt) was assessed by means of the light-darkness discrimination test when the animals reached maturity. Early shunt placement resulted in marked reduction in size of abnormally enlarged ventricles and the prevention of both decreasing spine density and decay of synaptic vesicle protein (SVP-38) in the affected cerebral cortex. The learning ability of such animals was also found not to be impaired compared with that of animals in a sham-operation group. On the basis of these investigations, it is concluded that early shunt placement may have a beneficial role in preventing not only impairment of synaptogenesis of the brain by progressing hydrocephalus, but also learning disability. Recent biochemical investigation of the developing brains of hydrocephalic HTX rats revealed problems that cannot be resolved by early shunt insertion, and these are also discussed.

Animals↗

PubMed2002

Age-related differences and the role of augmented visual feedback in learning a bimanual coordination pattern.

The purpose of this study was to investigate the effects of aging and the role of augmented visual information in the acquisition of a new bimanual coordination pattern, namely a 90 degrees relative phase pattern. In a pilot study, younger and older adults received augmented visual feedback in the form of a real-time orthogonal display of both limb movements after every fifth trial. Younger adults acquired this task over three days of practice and retained the task well over periods of one week and one month of no practice while the older adults showed no improvement at all on the task. It was hypothesized that the amount of augmented information was not sufficient for the older adults to overcome the strong tendency to perform natural, intrinsically stable coordination patterns, which consequently prevented them from learning the task. The present study evaluated the age-related role of augmented visual feedback for learning the new pattern. Participants were randomly assigned within age groups to receive either concurrent or terminal visual feedback after every trial in acquisition. In contrast to the pilot study, all of the older adults learned the pattern, although not to the same level as the younger adults. Both younger and older adults benefitted from concurrent visual feedback, but the older adults gained more from the concurrent feedback than the younger adults, relative to terminal feedback conditions. The results suggest that when learning bimanual coordination patterns, older adults are more sensitive to the structure of the practice conditions, particularly the availability of concurrent visual information. This greater sensitivity to the learning environment may reflect a diminished capacity for inhibitory control and a decreased ability to focus attention on the salient aspects of learning the task.

Adult↗