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Results for “Learning Curve”

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At least 919 records · Page 51Linked to original sources

PubMed1996

A randomized, double blind, controlled trial of tocolysis to assist external cephalic version in late pregnancy.

BACKGROUND: External cephalic version at term is not always successful. This trial was done to ascertain whether tocolysis has any effect on the success rate. METHODS: A randomized, double blind, controlled trial, with continuous paired sequential analysis. Fifty-one consecutive patients with a singleton fetus in a breech presentation between 36 and 38 weeks gestation, external version being attempted on each. Ritodrine infusion or placebo was infused before attempt at external cephalic version. SETTING: A university teaching hospital with 8000 confinements annually. RESULTS: Version was successful in 17 of the 25 patients given tocolysis, but in only eight of the 25 given placebo (p < 0.01). A positive benefit for tocolysis was shown after version had been completed in 10 pairs of patients. However the trial was continued until 25 pairs had been analyzed. The benefit deteriorated during analysis of the last 15 pairs suggesting that the initial benefit may reflect a learning curve for the procedure. CONCLUSION: Tocolysis is likely to improve the success rate of external cephalic version in late pregnancy, especially in nulliparous mothers or where doctors are learning the technique.

Adult↗

PubMed1990

How much practice makes perfect? A quantitative measure of the experience needed to achieve procedural competence.

Based on the general learning curve formula, the authors have devised a method to estimate the experience needed to achieve competence in the performance of medical and surgical procedures. The method quantitates the learning ability of the trainee, the technical difficulty of the procedure, and the expected level of competence. Two retrospective applications demonstrate the ease of use and reliability of the method.

Clinical Competence↗

PubMed2005

Sentinel lymph node biopsy. Preferred method of axillary staging for breast cancer.

Sentinel lymph node (SLN) biopsy has replaced routine axillary lymph node dissection (ALND) for most breast cancer patients with clinically normal lymph nodes. The morbidity (lymphedema, arm numbness) of SLN biopsy is significantly less than ALND. The use of alternative injection sites (skin or subareolar) yields high SLN identification rates and may shorten the learning curve associated with standard peritumoral injection. The dual-agent (radiocolloid plus blue dye) technique is recommended to decrease false-negative rates, especially when surgeons are just learning how to perform SLN biopsy. Regardless of the technique employed, SLN identification rates should be > 95% with a false-negative rate of < 5%. Using serial sectioning and immunohistochemistry, SLN micrometastases can be identified in 10% to 20% of node-negative patients. However, the clinical significance of micrometastases is not known. Axillary recurrence is rare for patients without SLN metastases who do not undergo further axillary surgery. Outside a clinical trial, ALND is recommended for most patients with SLN metastases, except for cases with SLN metastases < 0.2 mm detected by immunohistochemistry alone. The indications for SLN biopsy have expanded and include breast cancer patients with multifocal/multicentric disease and large tumors, and male breast cancer. Although minimally invasive internal mammary SLN biopsy is feasible, the usefulness of this procedure is not established.

Axilla↗

PubMed2002

Why aggregated learning follows the power law of practice when individual learning does not: comment on Rickard (1997, 1999), Delaney et al. (1998), and Palmeri (1999).

The power law of practice is often considered a benchmark test for theories of cognitive skill acquisition. Recently, P. F. Delaney, L. M. Reder, J. J. Staszewski, and F. E. Ritter (1998), T. J. Palmeri (1999), and T. C. Rickard (1997, 1999) have challenged its validity by showing that empirical data can systematically deviate from power-function fits. The main purpose of the present article is to extend their explanations in two ways. First, the authors empirically show that abrupt changes in performance are not necessarily based on a shift from algorithm to memory-based processing, but rather and more generally, that they occur whenever a more efficient task strategy is generated. Second, the authors show mathematically and per simulation that power functions can perfectly fit aggregated learning curves even when all underlying individual curves are discontinuous. Therefore, the authors question conclusions drawn from fits to aggregated data.

Humans↗

PubMed2004

Technical advances in sentinel lymph node biopsy for breast cancer.

Technical advances in the past several years have simplified and improved sentinel lymph node (SLN) biopsy for breast cancer. The use of alternative injection sites (skin or subareolar) yields high SLN identification rates and may shorten the learning curve associated with standard peri-tumoral injection. The dual-agent (radiocolloid plus blue dye) technique is now recommended to decrease false-negative rates, especially when surgeons are just learning how to perform SLN biopsy. Methylene blue may be an acceptable substitute for isosulfan blue dye and is associated with fewer hypersensitivity reactions. Hand-held gamma probes are now smaller and more maneuverable, with better shielding for directional detection of gamma rays. Routine preoperative lymphoscintigraphy can be avoided, thus facilitating operating room scheduling. Surgeons can use minimally invasive techniques to identify and remove internal mammary SLNs.

Breast Neoplasms↗

PubMed1996

Hippocampus and learning: possible role of histamine receptors.

The effect of local administration of histamine and its receptor antagonists into the hippocampus on the learning process of an active avoidance response was studied. The task that the animals had to learn consisted in avoiding an electric shock on their feet after a conditioning ultrasonic 40 kHz tone was on. Latency time was defined as the time in sec rats took to avoid or escape the electric shock: % CAR was defined as the cummulative positive responses during learning session. All rats were implanted into the ventral hippocampus with guide cannulae. On the day of the experiment, rats were microinjected through the guide cannulae with 1 microliter of saline solution containing 67.5 nmol of ranitidine or pyrilamine alone or in combination with 45 nmol of histamine. All groups were subjected to two sessions of learning. Results show that treatment with histamine was effective to block the adquisition of the response, since animals showed a learning curve significantly inferior to that of the controls. Ranitidine treatment was not able to block the histamine effect. Pyrilamine treatment, instead, was effective to block the inhibitory action of histamine on learning. Results suggest that histamine in hippocampus may be exerting a modulatory control on retrieval processes of memory.

Animals↗

PubMed1991

Development of a curriculum in colposcopy.

BACKGROUND: Colposcopy for the detection of genital malignancy and disease associated with human papillomavirus, along with cytologic screening and histopathologic correlation, allows for intervention before the onset of invasive disease. Family physicians are interested in learning colposcopy, but there are few reports in the literature on the training of colposcopists. METHODS: A colposcopy curriculum for family physicians was designed with goals, objectives, and instructional strategies selected to enhance learning and quality assurance of the current principles of colposcopic evaluation. During the pilot project, a third-year resident studied a syllabus and reviewed slides, practiced performance skills, and observed colposcopies. After demonstrating competence, the resident evaluated patients with instructor supervision and feedback. RESULTS: Resident performance data from written test scores and a performance checklist indicated an excellent learning curve. High resident satisfaction was reported. Suggestions from expert reviewers were incorporated into the final curriculum product. The evaluation data indicated that, based on this pilot program, family practice residents can effectively learn colposcopy. CONCLUSIONS: Colposcopy is a highly technical skill that can be learned by family physicians through professional training. Competency in colposcopy can provide a new dimension to their practice in the diagnosis and treatment of female lower-genital-tract disease. This colposcopy curriculum is an initial effort in the identification of the content and process required to train family physicians in the use of this diagnostic procedure.

Clinical Competence↗

PubMed2003

Task-specific perceptual learning on speed and direction discrimination.

Twenty-two nai;ve undergraduates participated in a psychophysical experiment designed to elucidate the neural events that allow us to see subtle motion differences. Half of the subjects practiced extensively on a direction-discrimination task while the other half practiced extensively on a speed-discrimination task. The stimulus conditions in the two groups were identical. The results indicated that the learning curves for direction discrimination were significantly steeper than those for speed discrimination. Additionally, the significant practice-based improvements on each motion task did not transfer to the other motion task. The different learning rates and the lack of transfer suggest that the neural events mediating speed discrimination are at least partially independent from those mediating direction discrimination, and vice versa, even under identical stimulus conditions.

Discrimination Learning↗

PubMed2004

Comparative psychometric analysis of vector and isochrone cardiac activation maps.

Isochronal cardiac activation maps can be constructed from local activation times associated with spatial locations, and are frequently used to study cardiac arrhythmias. Cardiac velocity vector mapping has been proposed as an alternative method to study cardiac activation in both clinical and research environments. Velocity vectors inherently contain more information than scalar measures of latency, but it is unknown how vector maps and isochronal maps compare when they are used to identify patterns and features associated with arrhythmias. In order to quantitatively compare these two visualization methods, eight cardiologists were asked to complete forced-choice tasks in which they selected ablation sites based on synthetic vector or isochronal maps. Maps varied in arrhythmia complexity, number of vectors or activation times included, and errors in magnitude or angle for maps of velocity vectors. Quantitative comparison was achieved by using psychometric functions to characterize the learning curve and the total number of measurements needed in order to choose a correct ablation site. For simple arrhythmias, performance with vector maps was superior to isochronal maps. Subjects required fewer measurements, and learned more rapidly by studying vector maps. For more complex arrhythmias, there was no significant difference in performance between vector and isochronal maps. However, arrhythmia features were clearer with vector maps, even though this clarity did not necessarily change the ablation site choice. When errors were added to vector maps, performance was satisfactory for angle errors < 55 degrees, and speed errors did not affect performance.

Arrhythmias, Cardiac↗

PubMed2001

Learning in networks of cortical neurons.

The results presented here demonstrate selective learning in a network of real cortical neurons. We focally stimulate the network at a low frequency (0.3-1 Hz) until a desired predefined response is observed 50 +/- 10 msec after a stimulus, at which point the stimulus is stopped for 5 min. Repeated cycles of this procedure ultimately lead to the desired response being directly elicited by the stimulus. By plotting the number of stimuli required to achieve the target response in each cycle, we are able to generate learning curves. Presumably, the repetitive stimulation is driving changes in the circuit, and we are selecting for changes consistent with the predefined desired response. To the best of our knowledge, this is the first time learning of arbitrarily chosen tasks, in networks composed of real cortical neurons, is demonstrated outside of the body.

Action Potentials↗

PubMedDate not supplied

First impressions: using an electronic utility for web-assisted teaching.

Using a web utility such as Blackboard to post handouts and announcements for students can better meet both student and instructor needs. Students can retrieve the handout whenever and wherever they want. Instructors can reduce the number of stored hard copy handouts (because they can be stored electronically) as well as reduce handout revision time (because they already are stored in electronic form). There is a learning curve to master for both students and instructors. Although this is not a perfect tool, it has the capacity to improve paper management issues for teachers, improve student access to documents and targeted supplemental learning aids, engage student interest in course content through technology, and encourage students to take responsibility for their own education. This article shares the authors' first impressions with using an electronic utility for web-assisted teaching.

Audiovisual Aids↗

PubMed1999

Medium-term results of a mobile bearing total knee replacement.

Mobile bearing total knee arthroplasty kinematically allows the advantages of large and congruent surface contact and low contact pressures, while preserving flexion, extension, and rotation in knee motion. In allowing for these degrees of freedom, the interface between bone and component also is protected from high stress. The Self Aligning I total knee arthroplasty initially was implanted in patients after its development at the authors' institution in 1990. Between 1990 and 1994, 141 patients with osteoarthritis of the knee underwent 172 total knee replacements using this system. At average followup of 5.6 years (range, 5-8 years), clinical results using this system showed a 94% satisfaction rate (good or very good). Two revision surgeries have been performed for polyethylene wear, with none of the remaining knees showing evidence of discernible wear. Complications included four cases of deep infection, four cases where a press fit femoral component failed (nonporous coated) and the patients required revision surgery, four traumatic fractures (three patellar and one supracondylar), one popliteal artery occlusion, and one revision for stiffness. Three patients required manipulation under anesthesia for arthrofibrosis. Kaplan-Meier survival curves show the probability of survival to be 91.7%, with revision surgery for any reason as an end point, and 98.8% for revision surgery because of polyethylene wear as an end point. Following the initial learning curve with this prosthesis, the medium term results using this system show maintenance of clinical success. No progressive evidence of polyethylene wear with time has been found, supporting the concept of mobile bearing arthroplasty in extending the service life of total knee arthroplasty.

Aged↗

PubMed2005

The influence of task demand and learning on the psychophysiological response.

The level of expertise of an operator may significantly influence his/her psychophysiological response to high task demand. A naive individual may invest considerable mental effort during performance of a difficult task and psychophysiological reactivity will be high compared to the psychophysiological response of a highly skilled operator. A study on multitasking performance was conducted to investigate the interaction between learning and task demand on psychophysiological reactivity. Thirty naive participants performed high and low demand versions of the Multi-attribute Task Battery (MATB) over a learning period of 64 min. High and low task demand setting were preset via a pilot study. Psychophysiological variables were collected from four channels of EEG (Cz, P3, P4, Pz), ECG, EOG and respiration rate to measure the impact of task demand and learning. Several variables were sensitive to the task demand manipulation but not time-on-task, e.g., heart rate, Theta activity at parietal sites. The sensitivity of certain variables to high demand was compromised by skill acquisition, e.g., respiration rate, suppression of alpha activity. A sustained learning effect was observed during the high demand condition only; multiple regression analyses revealed that specific psychophysiological variables predicted learning at different stages on the learning curve. The implications for the sensitivity of psychophysiological variables are discussed.

Adolescent↗

PubMed2005

The dynamics of perceptual learning: an incremental reweighting model.

The mechanisms of perceptual learning are analyzed theoretically, probed in an orientation-discrimination experiment involving a novel nonstationary context manipulation, and instantiated in a detailed computational model. Two hypotheses are examined: modification of early cortical representations versus task-specific selective reweighting. Representation modification seems neither functionally necessary nor implied by the available psychophysical and physiological evidence. Computer simulations and mathematical analyses demonstrate the functional and empirical adequacy of selective reweighting as a perceptual learning mechanism. The stimulus images are processed by standard orientation- and frequency-tuned representational units, divisively normalized. Learning occurs only in the "read-out" connections to a decision unit; the stimulus representations never change. An incremental Hebbian rule tracks the task-dependent predictive value of each unit, thereby improving the signal-to-noise ratio of their weighted combination. Each abrupt change in the environmental statistics induces a switch cost in the learning curves as the system temporarily works with suboptimal weights.

Brain↗

PubMed2006

Teaching robotic surgery: a stepwise approach.

BACKGROUND: After an initial institutional experience with 50 robot-assisted laparoscopic Roux-en-Y gastric bypass procedures, a curriculum was developed for fellowship training in robotic surgery. METHODS: Thirty consecutive robotic gastric bypasses were performed using the Zeus robotic surgical system to fashion a two-layer gastrojejunostomy. For teaching purposes, performance of the anastomosis was divided into three discrete tasks. Robotic suturing tasks were assigned to the trainee in cumulative order in ten-case increments. Our patient population averaged 44 years of age and 47 kg/m(2) in BMI. Patients were predominantly female (87%). RESULTS: The robotic training experience of the fellow defines the increases in surgical responsibility over the series of cases. Statistical analysis revealed no significant differences in task times or total robotic operative time as participation of the trainee in performing the gastrojejunostomy increased. No adverse robotic events or surgical complications occurred throughout this series. The learning curve of the fellow compared favorably with the initial experience of the institution. CONCLUSION: Robotic surgery training may be safely implemented in a minimally invasive surgery training program. A gradual introduction of robotic technique appears to maximize the learning experience and minimize the potential for adverse outcomes.

Adult↗

PubMed2002

Online learning: enhancing nurse education?

BACKGROUND: The need to integrate information technology into nursing education has been recognized and well documented. In spite of this, information technology remains a neglected subject in many nursing programmes. Strategies have been considered for increasing the integration of information technology in nursing education. One of the key issues identified is the need for research into the factors that contribute to optimal learning with information technology, specifically the need to explore issues that contribute to student frustration and satisfaction with learning. Within Australia, the incorporation of information technology as a core subject in nursing education is still relatively new. This article describes how one university used 'online' learning to expose students to conceptual and experiential opportunities that enabled them to develop skills in the management of information technology. METHODS: Twenty-one students participated in this qualitative study. Individual interviews were used to develop insights into student perceptions. Thematic analysis enabled refined themes to emerge. These themes formed the basis of focus group discussions. Focus groups were used to enhance and validate the information from one-to-one interviews by using group dynamics to add experiential richness to the data. FINDINGS: Four major themes emerged: computer confidence, flexibility, active learning and practicalities of teaching. CONCLUSIONS: The integration of information technology into nursing education requires a dramatic change in thinking. The 'learning curve' is steep for both student and educator and there are many issues that need to be considered. This research does not aim to provide solutions to the issues highlighted but rather offers recommendations for enhancing the teaching and learning experience.

Attitude of Health Personnel↗

PubMed2000

A stepwise approach to laparoscopic Nissen fundoplication: avoiding technical pitfalls.

Laparoscopic Nissen fundoplication is now widely used in the surgical management of gastroesophageal reflux disease. However, it is a complex operation that requires advanced laparoscopic skills. The learning curve is steep, and complications are directly related to the surgeon's experience level. Both experimental and clinical data demonstrate a decline in complications with increasing experience. We divided this complex procedure into logical and orderly components, to facilitate the learning process. We believe that this approach will not only reduce complications by highlighting potential problems at each stage but also make it easier to teach others.

Fundoplication↗

PubMedDate not supplied

Distributed synchrony in a cell assembly of spiking neurons.

We investigate the formation of a Hebbian cell assembly of spiking neurons, using a temporal synaptic learning curve that is based on recent experimental findings. It includes potentiation for short time delays between pre- and post-synaptic neuronal spiking, and depression for spiking events occurring in the reverse order. The coupling between the dynamics of synaptic learning and that of neuronal activation leads to interesting results. One possible mode of activity is distributed synchrony, implying spontaneous division of the Hebbian cell assembly into groups, or subassemblies, of cells that fire in a cyclic manner. The behavior of distributed synchrony is investigated both by simulations and by analytic calculations of the resulting synaptic distributions.

Action Potentials↗