Bayes Window (3): where do prior probabilities come from?
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Bayes Theorem↗
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Essential fatty acid preparation improves biochemical and cognitive functions in experimental allergic encephalomyelitis rats.
This study examined the possible effects of a novel mixture of fatty acids, SR-3 (a specific ratio of alpha-linolenic acids), on brain biochemistry and on learning deficits induced by injection of an agent that induces experimental allergic encephalomyelitis. Treatment with SR-3 caused a decrease in myelin and changes in the fatty acid profile of brain synaptosomes, and a learning deficit. Eighteen days of treatment with SR-3 reversed the biochemical and learning deficit significantly, but did not restore them to normal levels. We propose that, most probably, the main action of SR-3 is the modulation of the cholesterol level, which in turn causes the modulation of the fatty acid profile and enhances learning by allowing improved neuronal communication.
Analysis of Variance↗
Implicit sequence learning without motor sequencing in young and old adults.
The ability to detect patterns and organize individual events into complex sequences is a fundamental cognitive skill that is often learned implicitly. The serial response time (SRT) task has been widely used to investigate implicit sequence learning, but it remains unclear whether people learn a perceptual or motor sequence in this task. This study reports three experiments that build on previous research by Goschke and colleagues using an auditory SRT task in which the stimulus-to-response mapping changes on every trial to eliminate spatio-motor sequencing. The current study extends earlier work in three ways. First, healthy young and older adults were tested rather than the neuropsychological patients used in previous research. Second, sequences of different structural complexity were investigated including first- and second-order repeating sequences as well as higher-order probabilistic sequences. Third, the potential role of explicit knowledge was examined using three separate tests of declarative knowledge. Results indicate that young and old adults are able to learn purely perceptual auditory sequences, but that explicit knowledge contributes to learning of repeating sequences by young adults.
Acoustic Stimulation↗
Stereotactic breast biopsy: a surgical series.
BACKGROUND: Stereotactic core needle biopsy (SCNB) is increasing in popularity and is currently being performed by both radiologists and surgeons. It has been shown to be accurate and cost effective, but the appropriate use of SCNB in the probably benign mammographic lesion has not been determined. Nor has it been determined whether a learning curve affects performance of the procedure. STUDY DESIGN: The records of all patients undergoing SCNB by the author from August 1993 through May 1996 were reviewed. Two hundred forty-two patients underwent 244 procedures. Indications for biopsy, results, and complications were examined. RESULTS: Probably benign mass was the most common indication for biopsy (45%), and microcalcifications were the indication for biopsy in 24%. A diagnosis of cancer was made in 11.1%. Patients with microcalcifications and probably benign masses were diagnosed with cancer in 18.4 and 1.8%, respectively. Three of eight patients undergoing open biopsy for atypical hyperplasia were diagnosed with cancer. Accuracy rate for the entire series was 97.7%. The effect of operator experience on the indication for SCNB was studied. As experience increased from the first to the last third of the study, microcalcifications as an indication increased from 23.5-37.5%. During this same time period, "probably benign" mass decreased from 53.1-32.5%. CONCLUSION: This study demonstrates that accuracy of this surgical series is comparable to other published series. Biopsies for more difficult lesions were noted to increase as operator experience increased. It was likely that this "learning curve" was owing to improvements in technique and an increased confidence in the accuracy of the procedure. With an incidence of cancer of less than 2% in patients with a probably benign mass, interval mammography represents for many, a cost-effective alternative.
Biopsy, Needle↗
Spatio-temporal plasticity of cortical receptive fields in response to repetitive visual stimulation in the adult cat.
Many psychophysical experiments on perceptual learning in humans show increases of performance that are most probably based on functions of early visual cortical areas. Long-term plasticity of the primary visual cortex has so far been shown in vivo with the use of visual stimuli paired with electrical or pharmacological stimulation at the cellular level. Here, we report that plasticity in the adult visual cortex can be achieved by repetitive visual stimulation. First, spatial receptive field profiles of single units (n=38) in area 17 or 18 of the anesthetized cat were determined with optimally oriented flashing light bars. Then a conditioning protocol was applied to induce associative synaptic plasticity. The receptive field center and an unresponsive region just outside the excitatory receptive field were synchronously stimulated ('costimulation', repetition rate 1 Hz; for 10-75 min). After costimulation the receptive field and its adjacent regions were mapped again. We observed specific increases of the receptive field size, changes of the receptive field subfield structure as well as shifts in response latency. In 37% of the cells the receptive field size increased specifically towards the stimulated side but not towards the non-stimulated opposite side of the receptive field. In addition, changes in the relative strength and size of the on and off subfield regions were observed. These specific alterations were dependent on the level of neuronal activity during costimulation. During recovery, the new responses dropped down to 120% of the preconditioning value on average within 103 min; however, the decay times significantly depended on the response magnitude after costimulation. In the temporal domain, the latency of new responses appeared to be strongly influenced by the latency of the response during costimulation.Twenty-nine percent of the units displayed no receptive field enlargement, most likely because the activity during costimulation was significantly lower than in the cases with enlarged receptive fields. An unspecific receptive field enlargement towards both the stimulated and non-stimulated side was observed in 34% of the tested cells. In contrast to the cells with specifically enlarged receptive fields, the unspecific increase of receptive field size was always accompanied by a strong increase of the general activity level. We conclude that the receptive field changes presumably took place by strengthening of synaptic inputs at the recorded cells in a Hebbian way as previously shown in the visual cortex in vitro and in vivo. The observed receptive field changes may be related to preattentive perceptual learning and could represent a basis of the 'filling in' of cortical scotomas obtained with specific training procedures in human patients suffering from visual cortex lesions.
Animals↗
Pros and cons of vertical integration between clinical medicine and basic science within a problem-based undergraduate medical curriculum: examples and experiences from Linköping, Sweden.
Problem-based learning (PBL), combined with early patient contact, multiprofessional education and emphasis on development of communications skills, has become the basis for the medical curriculum at the Faculty of Health Sciences in Linköping (FHS), Sweden, which was started in 1986. Important elements in the curriculum are vertical integration, i.e. integration between the clinical and basic science parts of the curriculum and horizontal integration between different subject areas. This article discusses the importance of vertical integration in an undergraduate medical curriculum, according to experiences from the Faculty of Health Sciences in Linköping, and also give examples on how it has been implemented during the latest 15 years. Results and views put forward in published articles concerning vertical integration within undergraduate medical education are discussed in relation to the experiences in Linköping. Vertical integration between basic sciences and clinical medicine in a PBL setting has been found to stimulate profound rather than superficial learning, and thereby stimulates better understanding of important biomedical principles. Integration probably leads to better retention of knowledge and the ability to apply basic science principles in the appropriate clinical context. Integration throughout the whole curriculum entails a lot of time and work in respect of planning, organization and execution. The teachers have to be deeply involved and enthusiastic and have to cooperate over departmental borders, which may produce positive spin-off effects in teaching and research but also conflicts that have to be resolved. The authors believe vertical integration supports PBL and stimulates deep and lifelong learning.
Biological Science Disciplines↗
Associative and perceptual learning and the concept of memory systems.
An introductory review is followed by some new experimental data and a final discussion. The primate temporal lobe contains multiple qualitatively distinct memory systems. The functional properties of these memory systems can be explained by reference to the nature of the afferent information which they process, rather than by reference to any putative specialization in memory processing. In this way, the plasticity of 'memory systems' in associative memory is probably similar in principle to the plasticity of 'perceptual systems' in perceptual learning. Therefore, it is important to consider the relationship between perceptual and associative learning. Two experiments investigated perceptual learning in the Rhesus monkey (Macaca mulatta). Substantial perceptual learning was observed both with complex scenes and with simple colours. Two hypotheses as to the basis of perceptual learning are discussed. A physiological hypothesis is that training with a particular set of stimuli expands the cortical representation of those stimuli. This can explain the effects in both experiments. A psychological hypothesis is that perceptual learning is produced by learned associations among multiple features of complex stimuli. This can explain the effects in Expt. 1 but not in Expt. 2. The psychological associative hypothesis is therefore redundant. Furthermore, associative learning can itself be viewed as an expansion of the cortical representation of a complex event. Thus, the distinction between perceptual and memory systems will need to be abandoned as deeper understanding of cortical plasticity is achieved.
Animals↗
The rise of the boy-genius: psychological neoteny, science and modern life.
The mid-20th century saw the rise of the boy-genius, probably because a personality type characterized by prolonged youthfulness is advantageous both in science and modern life generally. This is the evolution of 'psychological neoteny', in which ever-more people retain for ever-longer the characteristic behaviours and attitudes of earlier developmental stages. Whereas traditional societies are characterized by initiation ceremonies marking the advent of adulthood, these have now dwindled and disappeared. In a psychological sense, some contemporary individuals never actually become adults. A child-like flexibility of attitudes, behaviours and knowledge is probably adaptive in modern society because people need repeatedly to change jobs, learn new skills, move to new places and make new friends. It seems that this adaptation is achieved by the expedient of postponing cognitive maturation - a process that could be termed psychological neoteny. ('Neoteny' refers to the biological phenomenon whereby development is delayed such that juvenile characteristics are retained into maturity.) Psychological neoteny is probably caused by the prolonged average duration of formal education, since students' minds are in a significant sense 'unfinished'. Since modern cultures favour cognitive flexibility, 'immature' people tend to thrive and succeed, and have set the tone of contemporary life: the greatest praise of an elderly person is to state that they retain the characteristics of youth. But the faults of youth are retained with well as its virtues: short attention span, sensation- and novelty-seeking, short cycles of arbitrary fashion and a sense of cultural shallowness. Nonetheless, as health gets better and cosmetic technologies improve, future humans may become somewhat like an axolotl - the cave-dwelling salamander which retains its larval form until death.
Beginning of Human Life↗
Disrupting circadian rhythms in rats induces retrograde amnesia.
Disrupting circadian organization in rats by phase-shifting the illumination cycle or by exposure to a reversed day/night cycle or to continuous light, resulted in retrograde amnesia for passive avoidance behavior. This retrograde amnesia induced by phase-shifting lasted at least 2 days, and gradually diminished the longer the rats were exposed to the new illumination cycle. Retention performance was not impaired when rats were exposed to phase-shifting for 3-5 days before the learning trial. The retrograde amnesia due to changing the illumination cycle is probably due to retrieval disturbances. Extinction of active avoidance behavior was facilitated in rats exposed to a phase-shifted illumination cycle, but social and explorative behavior of rats tested in dyadic encounters were not affected by changing the normal illumination cycle. It is concluded that phase-shifting may result in amnesia for newly learned behavioral responses, but not for more innate behavioral patterns.
Amnesia↗
The continuing medical education needs of anaesthetists.
Learning needs assessment is the term applied to the process of identifying or diagnosing a learner's educational needs. It is the foundation of a systematic continuing medical education (CME) programme. Needs assessment has been identified as the most pressing problem of medical education directors in North America. Furthermore, the CME learning needs, interests or motivations of anaesthetists have never been studied. The amount of time and effort required for needs assessment is probably a major deterrent to this activity. The investigators adopted simple and straightforward means of assessing the "perceived learning needs" and topic interests of anaesthetists. Questionnaires were sent by mail to anaesthetists practicing in teaching and non-teaching hospitals in the Toronto area. The questionnaire presented a list of CME content areas. The respondents were asked to indicate on scale of 1 to 10 their Current Expertise, Ideal-Desired Expertise, and Interest-Motivation levels for each content area. Need Score for each content area was calculated by taking the difference between Ideal and Current Expertise responses. A total of 101/305 anaesthetists (29%) responded to the survey. Most of the respondents had been in anaesthesia practice for less than ten years. Regional nerve block, acute pain control, and medicolegal considerations received high overall ranks in both the need and interest categories. Paediatric anaesthesia, anaesthesia for trauma surgery and thoracic anaesthesia had top ranks among the subspecialty fields. Regional anaesthesia techniques received higher need and interest ranks than intravenous and inhalational techniques. The learning needs of anaesthetists of a large urban centre have been identified, and this information is useful to CME planners.
Anesthesiology↗
Synergistic interactions between two skeletal mutations in mice: individual and combined effects of the semidominants cleidocranial dysplasia (Ccd) and short digits (Dsh).
Heterozygotes for cleidocranial dysplasia (Ccd) and short digits (Dsh) were crossed to test whether synergistic interactions occur between different dominant mutations whose individual pleiotropic phenotypic effects exhibit a common feature. These unlinked mutations are homozygous lethal, and they are congenic on the C57BL/10 background. Each mutation caused more than 10 different anomalies and showed variable expressivity. Each mutation produced several malformations that were present in every heterozygote. Seven different synergistic interactions were found, including one that yielded an entirely new abnormality not predicted from any abnormalities found in either of the single heterozygotes. Although synergistic interactions between dominant mutations have not, to our knowledge, been described in humans, these findings in mice increase the probability that they occur in humans. Under certain circumstances in human populations, the segregation of mutations causing synergistic interactions of the type demonstrated might be confused with recessive inheritance. It will be important to learn whether synergistic interactions can occur between other mutations. If they can, it will probably become important to take synergistic interactions into account when estimating the genetic hazards to humans from mutagens. Three antagonistic interactions were also found.
Animals↗
A behavioral study of the beetle Tenebrio molitor infected with cysticercoids of the rat tapeworm Hymenolepis diminuta.
The host-parasite relationship, Tenebrio molitor-Hymenolepis diminuta, was analyzed. The learning behavior of infected and uninfected (control) beetles in a T-maze was compared. The infected beetles moved much slower in the T-maze than the controls. The infected beetles reached the same level of learning as the controls. However, they needed more trials than the controls. The effect of the infection was already distinct after the first week and even higher after the second week. This indicates that the initial phase of infection caused stress in the beetles. Longer infection did not worsen their ability to learn. Thus, the parasites clearly changed the behavior of their intermediate host and probably made them more susceptible to their final host, the rat.
Animals↗
A potential role of central insulin in learning and memory related to feeding.
1. Hypothalamic insulin (HI) is well known for its role in feeding regulation. In addition, its concentration is modified in response to meals. Recent studies suggest that brain insulin participates in memory processes, possibly through stimulation by glucose. 2. The present microdialysis study focused on local in vivo regulation of HI by glucose and on the effects of aging on HI, since aging is characterized by deterioration of memory, body weight regulation, and central glucose utilization. Glucose (8 mM) infused for 5 min increased extracellular HI levels rapidly, by 4.6-fold, and cerebellar insulin levels by 0.4-fold only, suggesting a specific area-dependent regulation of HI by glucose. Neither insulinemia nor glycemia were affected, suggesting a central mechanism. The same dose of glucose induced a modest (0.4-fold), delayed (45 min) increase in hypothalamic serotonin, suggesting that the effect of glucose on HI is independent of a previously defined local serotonin-induced insulin release. HI levels in old normal weight rats were half the levels of young rats. In genetically old obese (fa/fa) Zucker rats, HI concentration was 30% of that in young normal rats, suggesting a deterioration of HI availability when aging and obesity are combined. 3. The above results, in line with recent considerations on a potential role of central insulin in learning and memory, suggest particular effects of HI on feeding and memory and probably on a specific "memory for food."
Age Factors↗
Metric learning for text documents.
Many algorithms in machine learning rely on being given a good distance metric over the input space. Rather than using a default metric such as the Euclidean metric, it is desirable to obtain a metric based on the provided data. We consider the problem of learning a Riemannian metric associated with a given differentiable manifold and a set of points. Our approach to the problem involves choosing a metric from a parametric family that is based on maximizing the inverse volume of a given data set of points. From a statistical perspective, it is related to maximum likelihood under a model that assigns probabilities inversely proportional to the Riemannian volume element. We discuss in detail learning a metric on the multinomial simplex where the metric candidates are pull-back metrics of the Fisher information under a Lie group of transformations. When applied to text document classification the resulting geodesic distance resemble, but outperform, the tfidf cosine similarity measure.
Algorithms↗
Statistical computations over a speech stream in a rodent.
Statistical learning is one of the key mechanisms available to human infants and adults when they face the problems of segmenting a speech stream (Saffran, Aslin, & Newport, 1996) and extracting long-distance regularities (G6mez, 2002; Peña, Bonatti, Nespor, & Mehler, 2002). In the present study, we explore statistical learning abilities in rats in the context of speech segmentation experiments. In a series of five experiments, we address whether rats can compute the necessary statistics to be able to segment synthesized speech streams and detect regularities associated with grammatical structures. Our results demonstrate that rats can segment the streams using the frequency of co-occurrence (not transitional probabilities, as human infants do) among items, showing that some basic statistical learning mechanism generalizes over nonprimate species. Nevertheless, rats did not differentiate among test items when the stream was organized over more complex regularities that involved nonadjacent elements and abstract grammar-like rules.
Animals↗
Computer literacy in nursing education. An overview.
Nursing educators are beginning to realize that computer literacy has become a survival skill for the profession. They understand that literacy must be at a level that assures the ability to manage and control the flood of available information and provides an openness and awareness of future technologic possibilities. The computer has been on college campuses for a number of years, used primarily for record storage and retrieval. However, early on a few nurse educators saw the potential for its use as a practice tool. Out of this foresight came both formal and nonformal educational offerings. The evolution of formal coursework in computer literacy has moved from learning about the computer to learning with the computer. Today the use of the computer is expanding geometrically as microcomputers become common. Graduate students and faculty use them for literature searches and data analysis. Undergraduates are routinely using computer-assisted instruction. Coursework in computer technology is fast becoming a given for nursing students and computer competency a requisite for faculty. However, inculcating computer competency in faculty and student repertoires is not an easy task. There are problems related to motivation, resources, and control. Territorial disputes between schools and colleges must be arbitrated. The interface with practice must be addressed. The paucity of adequate software is a real concern. But the potential is enormous, probably restricted only by human creativity. The possibilities for teaching and learning are profound, especially if geographical constraints can be effaced and scarce resources can be shared at minimal cost. Extremely sophisticated research designs and evaluation methodologies can be used routinely.(ABSTRACT TRUNCATED AT 250 WORDS)
Computer-Assisted Instruction↗
Actual versus consistent decision behavior.
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Decision Making↗
Remission, recovery, relapse, and recurrence in eating disorders: conceptualization and illustration of a validation strategy.
In a consensus-building process a group of experts from 19 European countries (COST Action B6) adapted the terms partial and full remission, relapse, recovery, and recurrence according to principles described by Frank et al. for depression. The empirical validity of the operationalizations was illustrated by longitudinal data on the post treatment course of 233 anorectic and 422 bulimic patients (diagnosed according to DSM-IIIR) from the German Project TR-EAT. These data were collected 2.5 years after admission using the Longitudinal Interval Follow-up Evaluation (LIFE) and statistically explored by survival-analysis. It was demonstrated that these consensus definitions measure what they intend to measure. They open a longitudinal perspective in that one can learn not only whether, but also when and with what probability patients change for the better or worse. Data suggest that persistence of symptom improvement has different implications for anorexia and bulimia nervosa. For example, relapse prevention would be most beneficial for bulimic patients for about 4 months after key symptoms remit, while this would be of less importance for anorexic patients. It is discussed whether and how this longitudinal approach can contribute to an empirically based rationale for targeted and individualized treatment.
Adult↗