SEARCH · PubMed Health

Results for “Learning Curve”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources

PubMed1995

Quantitative standardised analysis of advanced laparoscopic surgical procedures.

To support the improvement of advanced laparoscopic surgical procedures, we designed a quantitative analysis method to monitor surgical activities. The emphasis lies on the time spent on these activities and on the instruments controlled by the hands of the surgeon. Our method uses combined video images originating from the laparoscope, an overview CCD camera placed in the operating theatre and, when available, a video colonoscope. After the operation is finished, the images are evaluated by means of a standardised analysis routine based on a spreadsheet program and a set of standard terms (thesaurus), to minimise subjectivity of the analysis. After calculations, the data are presented in tables and graphs, resulting in objective information for research on the operation. Seven advanced laparoscopic procedures, in this case colon resections, have been analysed, and it was demonstrated that the analysis method is capable of describing different laparoscopic procedures using the limited thesaurus. Possible areas of application of the method are the evaluation of time-consuming parts of the operation, of surgical tasks and measurement of the surgeon's learning curve. Other applications are the prediction and measurement of the impact of new instruments and techniques.

Colectomy↗

PubMed1988

Age-related sex differences in verbal memory.

Verbal learning and memory were studied in 196 healthy men and women aged 40 to 89. The Rey Auditory Verbal Learning Task (RAVLT), a 15-word list, was presented over five trials followed by free recall after each trial. A recognition trial of 50 words subsequently was administered. A stepwise regression that examined the contributions of age, sex, and vocabulary on the five trials of the RAVLT showed that age and sex accounted for a significant portion of the variance on each trial. Vocabulary accounted for a significant portion of the variance only on trials 4 and 5. The recognition trial was not affected by age, sex, or vocabulary. Men had lower scores overall as compared to women. In the older age group (ages 66-89), this difference was significant on trials two through five. Possible mechanisms that may underlie these age-related sex differences in learning curves are discussed.

Adult↗

PubMed1996

Effects of psychotropic drugs on rat responding in an operant paradigm involving choice between delayed reinforcers.

Preference for immediate reward, taken as an index of impulsiveness, has been suggested to be under the preferential control of central serotonin (5-HT) function. The present study examined the effects of the acute administration of drugs which directly or indirectly alter 5-HT transmission on tolerance to delay of reward in rats subjected to a procedure of discrete-trial choice in an operant chamber. Different groups of rats were trained to choose between two levers giving access to reinforcers differing in both magnitude and delay: one food pellet, delayed by 0 or 5 s, vs. five pellets delivered after a prereinforcer interval fixed at either 15, 30, 45, or 60 s, depending on the experiments. The learning curves indicated that rats were able to adjust their choice strategy precisely according to various factors: the respective duration of the delays before the small and large rewards, the immediacy of the small reward delivery, and the lengthening of the trials by a postreinforcer delay (or intertrial interval). Whatever the experimental parameters and stage of the learning, an acute administration of drugs able to reduce 5-HT neuronal activity (benzodiazepines; 5-HT1A receptor partial agonists: buspirone and MDL 73005EF) or enhance 5-HT transmission (5-HT reuptake inhibitors: indalpine and zimelidine; 5-HT1A receptor full agonist: 8-OH-DPAT) failed significantly to alter choice strategy (decreased or increased preference for the large but delayed reward, respectively), as they did in other situations such as a T-maze procedure. Only d-amphetamine (0.5 mg/kg), on one occasion, significantly reduced preference for the larger reward. The choice strategy was also insensitive to acute changes in experimental parameters such as a reduction in delay or increase in the magnitude of the large reinforcement. These results indicate that the present operant paradigm is not sensitive to acute modifications in the internal state of the animals and in the reward contingencies, and therefore is not useful to evaluate tolerance to delay and variations in impulsiveness in rats.

Animals↗

PubMed2001

Design principles for the use of simulation as an aid in interventional cardiology training.

Learning complex skills through simulation is a goal for training physicians in specialties such as interventional cardiology, where traditional training puts patients at risk. Intuitively, interactive simulation of anatomy, pathology and therapeutic actions should lead to shortening of the learning curve for novice or inexperienced physicians. An accurate recreation of the interactions among anatomy, pathology and therapeutic actions is a necessary, but not sufficient, condition for the development of a simulation-based training system. In addition to real-time graphic interactivity coupled with haptic response, a successful training tool will require features of a 'learning system' such as: an embedded curriculum, functionality that allows rehearsal and practice, hypertext links to educational information, personal archiving, and instructor review and testing capabilities. We describe how such a system might look for the field of interventional cardiology, and suggest that designing a simulation with both technical and pedagogical fidelity is essential in developing simulation-based training systems in any field of medicine.

Journal Article↗

PubMed1999

Blockade of N-methyl-D-aspartate receptors in the insular cortex disrupts taste aversion and spatial memory formation.

The present experiments examined the effects of direct intracortical microinjections of the N-methyl-D-aspartate receptor antagonist 2-amino-5-phosphonovaleric acid directly into the insular cortex of rats, before or immediately after training of conditioned taste aversion and the water maze spatial learning task. In the first series of experiments animals received bilateral injections of 2-amino-5-phosphonovaleric acid prior to taste aversion conditioning or spatial training. A strong disruptive effect was found in the acquisition of training tasks. To determine the possible involvement of N-methyl-D-aspartate receptors in the early post-training processes taking place in the cortex during both learning paradigms, in a second series of experiments, animals received bilateral 2-amino-5-phosphonovaleric acid microinjections 30, 60 or 120 min after the acquisition trial, and 15 min before the retention test. For spatial learning successive treatments were independently done either starting at the onset of the asymptotic phase of the learning curve, 0, 30 or 120 min after finishing the training session, as well as 15 min before the retention test trial. The conditioned taste aversion task remained sensitive to N-methyl-D-aspartate blockade during a period of at least 2 h after the first presentation of the gustatory stimulus, while in the case of the spatial learning task, a gradually decreasing effect was observed from the onset of the asymptotic phase onwards. Taken together, these results provide direct evidence for N-methyl-D-aspartate receptor involvement in cortical regulation of memory formation. Furthermore, our results suggest that in the same cortical region, a different time-course for the activation of N-methyl-D-aspartate-dependent mechanisms occurs during the early formation of cortically mediated memories, depending on the particular behavioural task.

2-Amino-5-phosphonovalerate↗

PubMed2005

Analysis of mean learning of normal participants on the Rey Auditory-Verbal Learning Test.

Analysis of the mean performance of 58 groups of normal adults and children on the free-recall trials of the Rey Auditory-Verbal Learning Test shows that the mean auditory-verbal learning of each group is described by the function R1 + Sln(t), where R1 is a measure of the mean immediate memory span, S is the slope of the mean logarithmic learning curve, and ln(t) is the natural logarithm of the trial number t. The analysis also shows that R1 varies with age and other demographic factors, whereas S is almost a constant, and it yields equations for estimating the effect of these factors on R1. Potential use of these findings for assessment of auditory-verbal memory and learning in comparative clinical studies is discussed.

Adolescent↗

PubMed2003

Learning to control brain rhythms: making a brain-computer interface possible.

The ability to control electroencephalographic rhythms and to map those changes to the actuation of mechanical devices provides the basis for an assistive brain-computer interface (BCI). In this study, we investigate the ability of subjects to manipulate the sensorimotor mu rhythm (8-12-Hz oscillations recorded over the motor cortex) in the context of a rich visual representation of the feedback signal. Four subjects were trained for approximately 10 h over the course of five weeks to produce similar or differential mu activity over the two hemispheres in order to control left or right movement in a three-dimensional video game. Analysis of the data showed a steep learning curve for producing differential mu activity during the first six training sessions and leveling off during the final four sessions. In contrast, similar mu activity was easily obtained and maintained throughout all the training sessions. The results suggest that an intentional BCI based on a binary signal is possible. During a realistic, interactive, and motivationally engaging task, subjects learned to control levels of mu activity faster when it involves similar activity in both hemispheres. This suggests that while individual control of each hemisphere is possible, it requires more learning time.

Adaptation, Psychological↗

PubMed2001

Assessing laparoscopic manipulative skills.

BACKGROUND: The rapid emergence of laparoscopic surgery over the past decade has highlighted the need for teaching and assessing laparoscopic manipulative skills. Most analyses consist of a measurement of the time to complete a specified task and a subjective assessment by an observer. Objective assessments of accuracy in the performance of manipulative skills have been lacking. To quantify both speed and accuracy during laparoscopic skill performance, we have developed a skills assessment device (SAD) using a laparoscopic simulator platform and computer-based skills assessment software that precisely measures an instrument's movement during performance of timed laparoscopic manipulations. STUDY DESIGN: The SAD device measures the time necessary for an operator to complete a task, and the movements of the working end of laparoscopic instruments in three dimensions. Ten nonsurgeons performed 10 repetitions of a standardized laparoscopic manipulation. Data were captured in real time for both hands on a personal computer. Accuracy was determined by calculating the sum of all distances traveled. Duration was measured in seconds. Results are group means. RESULTS: The time necessary to perform defined laparoscopic manipulative skills improved dramatically during the first 3 repetitions and then stabilized. However, accuracy of manipulations continued to improve over all 10 repetitions. CONCLUSIONS: When untrained subjects are learning a laparoscopic manipulative task, measurement of time alone fails to account for the more protracted learning curve for accuracy. Therefore, devices and training programs that fail to consider objective assessments of accuracy may overestimate laparoscopic proficiency.

Clinical Competence↗

PubMed1998

Evaluation of an ultrasonically guided venepuncture technique for the placement of permanent pacing electrodes.

We have evaluated a method of puncturing the subclavian vein in its extrathoracic portion using an ultrasound guidance system. Seventy consecutive patients requiring permanent pacemakers were included in the study. The method was successful in 56 (80%) cases (23 dual chamber systems) and unsuitable or unsuccessful in 14 (20%) cases (2 dual chamber systems). The time taken to achieve a successful cannulation of the vein was similar to that taken with conventional subclavian venepuncture (average time taken for each venepuncture was 31 seconds, range 5-130 seconds). There was a significant "learning curve" in that nearly all of the unsuccessful cases were in the first half of the series. There were no major complications. Computerized Tomography (CT) confirms that the point of entry into the subclavian vein using this technique lies outside the thoracic cavity, thereby minimizing the risk of pneumothorax. This approach to the subclavian vein is an easy technique to learn, with few immediate complications and there may be less chance of lead fracture due to subclavian crush in the longer term.

Adult↗

PubMed1999

Laparoscopic anterior lumbar interbody fusion. Technical note.

In recent years, there has been an unprecedented increase in the number of patients undergoing treatment with interbody fusion devices for degenerative disease of the lumbar spine. These devices can be placed either anteriorly or posteriorly. With the advent of minimally invasive surgery and the increasing ability of general surgeons to perform transperitoneal procedures laparoscopically, a new laparoscopic technique has been developed for placing lumbar interbody fusion devices. Although this procedure has some advantages over posterior lumbar interbody fusion, it is not without significant risk, and the learning curve is steep. The authors review a series of 32 consecutive patients who underwent single-level laparoscopic anterior lumbar interbody fusion at L4-5 or L5-S1 over a 2-year period for the treatment of single-level lumbar degenerative disease. In this report they review the technical aspects of the procedure and the important lessons they have learned through their early experience with this technique.

Journal Article↗

PubMed1999

Aging and corticosterone injections affect spatial learning in Fischer-344 X Brown norway rats.

The hippocampus is one of the first brain structures to show age-related changes. Moreover, hippocampal neurons are endangered by prolonged exposure to high circulating levels of corticosterone with stress or aging. We examined the effects of aging and high corticosterone levels on spatial learning, a key hippocampal function. Young (4-6 months), old (23-25 months), and very old (31 months) male Fischer-344xBrown Norway (F-344xBN) rats received six pre-testing days in the Morris water task to determine baseline spatial learning performance. Next, half the animals in each group were given daily corticosterone injections for 15 days. During the last six injection days, all animals underwent post-testing in the Morris water task with the environment and goal location changed. Baseline, peak, and clearance plasma corticosterone levels were determined. During pre-testing, old animals swam as directly to the goal as the young, but very old animals were significantly impaired. During post-testing, both old and very old non-injected animals had significantly greater directional heading errors and flatter learning curves than the young. Among injected animals, the very old performed as well as the young, but the old did not. Old animals who did not show improvement during the first three pre-testing days were responsible for the old impairment during post-testing. Thus, only very old F-344xBN rats are impaired when initially exposed to a spatial learning task, but half the old and all very old animals are impaired when the environment is changed. Very old F-344xBN rats, however, demonstrate enhanced spatial learning when exposed to corticosterone injections.

Age Factors↗

PubMedDate not supplied

Knemometry in childhood: a study to compare the precision of two different techniques.

Knemometry is an accurate and non-invasive method of quantifying lower leg length changes. It reveals multiple fluctuations in leg length velocity over a short period of measurement, and on the basis of this it has been proposed that short-term growth is saltatory rather than a continuous phenomenon. The technical error (TE) of the technique which is generally employed, and which is subject to observer bias, ranges from 0.09 to 0.16 mm. This study was undertaken to compare the original method (OM) to a modified technique which involved measuring from a baseline value of which the operator was not aware; this technique is referred to as the random zero method (RM). Over a period of 10 months, 58 subjects were measured on 413 occasions. Overall, median TE in the RM group at 0.15 mm (P5-0, P95-0.65) was higher than the median TE in the OM group at 0.11 mm (P5-0, P95-0.37). However, the median TE over the last 3 months of 0.15 mm (P5-0.05, P95-0.87) was lower than the TE in the preceding 4 months of 0.20 mm (P5-0, P95-0.55) (WSR, p = 0.04) pointing towards the presence of an operator learning curve. The random zero method is a simple modification of the original method. It reduces observer bias but leads to a higher TE, which could explain some of the fluctuations seen between frequent knemometric measurements. Some knowledge of the length of the training period is important in the design of new studies involving knemometry; our data suggest that there should be a learning period of about 4 months if knemometry is performed as often as quoted above.

Adult↗

PubMed1985

Genotype-environment interaction in passive avoidance learning of the paradise fish (Macropodus opercularis).

Passive dark avoidance conditioning and effects of the presence and absence of a fish-like dummy on the training process were studied in four inbred strains of paradise fish. Strain differences were found in the shuttle activity during habituation trials, and in the sensitivity to the mild electric shock punishment. The presence or absence of the dummy in the punished dark side of the shuttle box had a genotype-dependent effect on the measures taken during the conditioning process. The statistical analysis of the learning curves revealed differences in the way the strains varied in the different environments, i.e. genotype--environment interaction components of variances were identified. The results are discussed in the light of previous investigations and their implication in further genetic analysis.

Animals↗

PubMed2000

Remodeling of hippocampal synapses after hippocampus-dependent associative learning.

The aim of this study was to determine whether hippocampus-dependent associative learning involves changes in the number and/or structure of hippocampal synapses. A behavioral paradigm of trace eyeblink conditioning was used. Young adult rabbits were given daily 80 trial sessions to a criterion of 80% conditioned responses in a session. During each trial, the conditioned (tone) and unconditioned (corneal airpuff) stimuli were presented with a stimulus-free or trace interval of 500 msec. Control rabbits were pseudoconditioned by equal numbers of random presentations of the same stimuli. Brain tissue was taken for morphological analyses 24 hours after the last session. Synapses were examined in the stratum radiatum of hippocampal subfield CA1. Unbiased stereological methods were used to obtain estimates of the total number of synapses in this layer as well as the area of the postsynaptic density. The data showed that the total numbers of all synaptic contacts and various morphological subtypes of synapses did not change in conditioned animals. The area of the postsynaptic density, however, was significantly increased after conditioning in axospinous nonperforated synapses. This structural alteration may reflect an addition of signal transduction proteins (such as receptors and ion channels) and the transformation of postsynaptically silent synapses into functional ones. The findings of the present study indicate that cellular mechanisms of hippocampus-dependent associative learning include the remodeling of existing hippocampal synapses. Further studies examining various time points along the learning curve are necessary to clarify the issue of whether these mechanisms also involve the formation of additional synaptic contacts.

Animals↗

PubMedDate not supplied

[Robotic surgery: considerations after 250 procedures].

The aim of this study was to investigate the results of the first 250 procedures performed on 216 patients with the da Vinci Robotic Surgical System (34/216 patients were submitted to double procedure). The purpose of the da Vinci surgical system is to exactly translate the surgeon's hand movements to the robotic arms that manipulate the laparoscopic instruments, thus facilitating minimally invasive surgery. The da Vinci system has been available in our department since 2001. The first 50 procedures were simple cases (cholecystectomies and transperitoneal hernia repairs) and were performed during the learning curve of the surgical team. The last 200 procedures were more complex cases. Time of preparation of the robot gradually decreased with growing experience. The total conversion rate (to standard laparoscopy and to open surgery) was 4.8% (12/250); conversion to laparotomy was 2.8% (7/250). Morbidity was 8.8% (19/216), and reoperation was needed in 6 patients. Mortality was 1.8% (4/216). We conclude that robotic surgery has now moved beyond the learning phase with the device and may be routinely used in selected, more complex cases, such as colorectal surgery and surgery of the gastro-oesophageal junction. The device can also be used in pancreatic and gastric surgery.

Adult↗

PubMed2004

Short and long-term motor skill learning in an accelerated rotarod training paradigm.

Rodent models of motor skill learning include skilled forelimb reaching and acrobatic locomotor paradigms. This study characterizes motor skill learning in the accelerated rotarod task. Thirty Long-Evans rats (300-400 g) were trained on an accelerated rotarod (1cm/s(2)) over eight consecutive sessions (=days, 20 trials each). Improvement in rotarod velocities mastered before falling off the rod was observed within and between sessions (plateau after five sessions). Intrasession improvement was incompletely retained at the beginning of the next day's session. Over several training sessions, intrasession improvement diminished, suggesting a ceiling effect. After 1 week of pause, the rotarod skill was retained. Locomotor exercise in a running wheel for 30 min before the first rotarod session did not affect intrasession improvement. Running-wheel exposure for 6 days did not diminish the rate of rotarod skill learning (steepness of the learning curve) but improved overall performance (upward shift of curve). Video analysis of gait on the rotarod showed that rats developed a motor strategy by modifying their gait patterns during training. The data demonstrate that rotarod improvement is not the result of enhanced general locomotor ability or fitness, which are trained in the running wheel, but requires a change in the motor strategy to master the task. Accelerated rotarod training can be regarded a valid paradigm for motor skill learning over short (intrasession, minutes) and long time frames (intersession, days).

Analysis of Variance↗

PubMed2000

Limited auditory memory for conspecific songs in a non-territorial songbird.

Males of territorial songbird species have to remember a large number of conspecific songs to defend their territories, while non-territorial songbirds do not need to. A study of a territorial species suggested seemingly unlimited auditory memory size. We measured auditory memory in Bengalese finches, a non-territorial songbird species, to examine whether the auditory memory size for conspecific songs depends on the ecological requirements for song use. Five birds were trained by operant techniques to classify song stimuli into two arbitrary categories. The learning curve reached an asymptote within approximately 100 sessions in all five birds and only eight songs were concurrently remembered on average. Results suggest that ecological requirements for song use are correlated with the auditory song memory capacity.

Acoustic Stimulation↗

PubMed2006

Development and evaluation of a training module for the clinical introduction of the da Vinci robotic system in visceral and vascular surgery.

BACKGROUND: With the increasing use of the surgical robotic system in the clinical arena, appropriate training programs and assessment systems need to be established for mastery of this new technology. The authors aimed to design and evaluate a clinic-like training program for the clinical introduction of the da Vinci robotic system in visceral and vascular surgery. METHODS: Four trainees with different surgical levels of experience participated in this study using the da Vinci telemanipulator. Each participant started with an initial evaluation stage composed of standardized visceral and vascular operations (cholecystectomy, gastrotomy, anastomosis of the small intestine, and anastomosis of the aorta) in a porcine model. Then the participants went on to the training stage with the rat model, performing standardized visceral and vascular operations (gastrotomy, anastomosis of the large and small intestines, and anastomosis of the aorta) four times in four rats. The final evaluation stage was again identical to the initial stage. The operative times, the number of complications, and the performance quality of the participants were compared between the two evaluation stages to assess the impact of the training stage on the results. RESULTS: The operative times in the final evaluation stage were considerably shorter than in the initial evaluation stage and, except for cholecystectomies, all the differences reached statistical significance. Also, significantly fewer complications and improved quality for each operation in the final evaluation stage were documented, as compared with their counterparts in the initial evaluation stage. These improvements were recorded at each level of experience. CONCLUSIONS: The presented experimental small and large animal model is a standardized and reproducible training method for robotic surgery that allows evaluation of the surgical performance while shortening and optimizing the learning-curve.

Animals↗