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Results for “Simulation Training”

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At least 973 records · Page 54Linked to original sources

PubMed2000

Spike coding during locomotor network activity in ventrally located neurons in the isolated spinal cord from neonatal rat.

To characterize spike coding in spinal neurons during rhythmic locomotor activity, we recorded from individual cells in the lumbar spinal cord of neonatal rats by using the on-cell patch-clamp technique. Locomotor activity was induced by N-methyl-D aspartate (NMDA) and 5-hydroxytryptamine (5-HT) and monitored by ventral root recording. We made an estimator based on the assumption that the number of spikes arriving during two halves of the locomotor cycle could be a code used by the neuronal network to distinguish between the halves. This estimator, termed the spike contrast, was calculated as the difference between the number of spikes in the most and least active half of an average cycle. The root activity defined the individual cycles and the positions of the spikes were calculated relative to these cycles. By comparing the average spike contrast to the spike contrast in noncyclic, randomized spike trains we found that approximately one half the cells (19 of 42) contained a significant spike contrast, averaging 1.25 +/- 0.23 (SE) spikes/cycle. The distribution of spike contrasts in the total population of cells was exponential, showing that weak modulation was more typical than strong modulation. To investigate if this low spike contrast was misleading because a higher spike contrast averaged out by occurring at different positions in the individual cycles we compared the spike contrast obtained from the average cycle to its maximal value in the individual cycles. The value was larger (3.13 +/- 0.25 spikes) than the spike contrast in the average cycle but not larger than the spike contrast in the individual cycles of a random, noncyclic spike trains (3.21 +/- 0.21 spikes). This result suggested that the important distinction between cyclic and noncyclic cells was only the repeated cycle position of the spike contrast and not its magnitude. Low spike frequencies (5.2 +/- 0.82 spikes/cycle, that were on average 3.5 s long) and a minimal spike interval of 100-200 ms limited the spike contrast. The standard deviation (SD) of the spike contrast in the individual neurons was similar to the average spike contrasts and was probably stochastic because the SDs of the simulated, noncyclic spike trains were also similar. In conclusion we find a highly distributed and variable locomotor related cyclic signal that is represented in the individual neurons by very few spikes and that becomes significant only because the spike contrast is repeated at a preferred phase of the locomotor cycle.

Action Potentials↗

PubMed2005

Analyzing functional connectivity using a network likelihood model of ensemble neural spiking activity.

Analyzing the dependencies between spike trains is an important step in understanding how neurons work in concert to represent biological signals. Usually this is done for pairs of neurons at a time using correlation-based techniques. Chornoboy, Schramm, and Karr (1988) proposed maximum likelihood methods for the simultaneous analysis of multiple pair-wise interactions among an ensemble of neurons. One of these methods is an iterative, continuous-time estimation algorithm for a network likelihood model formulated in terms of multiplicative conditional intensity functions. We devised a discrete-time version of this algorithm that includes a new, efficient computational strategy, a principled method to compute starting values, and a principled stopping criterion. In an analysis of simulated neural spike trains from ensembles of interacting neurons, the algorithm recovered the correct connectivity matrices and interaction parameters. In the analysis of spike trains from an ensemble of rat hippocampal place cells, the algorithm identified a connectivity matrix and interaction parameters consistent with the pattern of conjoined firing predicted by the overlap of the neurons' spatial receptive fields. These results suggest that the network likelihood model can be an efficient tool for the analysis of ensemble spiking activity.

Action Potentials↗

PubMed1991

Establishment of a laparoscopic cholecystectomy training program.

A recently developed alternative to traditional laparotomy and cholecystectomy is laparoscopic-guided cholecystectomy. This procedure has the advantages of reduced hospital stay, early return to work, diminished abdominal wall scarring, and less patient discomfort. The complex nature of this procedure and the current lack of extensive clinical experience preclude the traditional "hands-on" training normally practiced in surgical residency programs. At the University of Maryland, we have developed a program to instruct both surgeons and surgical residents in the techniques of laparoscopic surgery. Technical competence is achieved under the close supervision and guidance of an experienced laparoscopic surgeon. Training of residents in this procedure, therefore, is not very different than that for other general surgical procedures. Surgeons already in clinical practice, however, gain experience under somewhat different circumstances. Initial training involves didactic instruction through laparoscopic surgical atlases and educational videotapes. Further training uses a simulation device which enables the trainee to practice techniques of laparoscopic suturing, knot-tying, and clip application. Actual operative experience is acquired primarily in experimental animal preparations. Laparoscopic-guided removal of the gallbladder is performed in young swine (20-25 kg) under conditions that mimic those in the operating room. Further clinical experience can be acquired by assisting on several laparoscopic operations, usually involving diagnostic or pelvic procedures. Actual operative experience with laparoscopic cholecystectomy, of course, comprises the final phase of the educational program. The introduction of clinical laparoscopic training into general surgery residency programs should influence the widespread adoption of this new procedure.

Cholecystectomy↗

PubMed2006

Encoding of time-varying stimuli in populations of cultured neurons.

We wondered whether random populations of dissociated cultured cortical neurons, despite of their lack of structure and/or regional specialization, are capable of modulating their neural activity as the effect of a time-varying stimulation - a simulated 'sensory' afference. More specifically, we used localized low-frequency, non-periodic trains of stimuli to simulate sensory afferences, and asked how much information about the original trains of stimuli could be extracted from the neural activity recorded at the different sites. Furthermore, motivated by the results of studies performed both in vivo and in vitro on different preparations, which suggested that isolated spikes and bursts may play different roles in coding time-varying signals, we explored the amount of such 'sensory' information that could be associated to these different firing modes. Finally, we asked whether and how such 'sensory' information is transferred from the sites of stimulation (i.e., the 'sensory' areas), to the other regions of the neural populations. To do this we applied stimulus reconstruction techniques and information theoretic concepts that are typically used to investigate neural coding in sensory systems.Our main results are that (1) slow variations of the rate of stimulation are coded into isolated spikes and in the time of occurrence of bursts (but not in the bursts' temporal structure); (2) increasing the rate of stimulation has the effect of increasing the proportion of isolated spikes in the average evoked response and their importance in coding for the stimuli; and, (3) the ability to recover the time course of the pattern of stimulation is strongly related to the degree of functional connectivity between stimulation and recording sites. These observations parallel similar findings in intact nervous systems regarding the complementary roles of bursts and tonic spikes in encoding sensory information.Our results also have interesting implications in the field of neuro-robotic interfaces. In fact, the ability of populations of neurons to code information is a prerequisite for obtaining hybrid systems, in which neuronal populations are used to control external devices.

Action Potentials↗

PubMed1995

Improving physicians' interviewing skills and reducing patients' emotional distress. A randomized clinical trial.

BACKGROUND: Despite high prevalence, emotional distress among primary care patients often goes unrecognized during routine medical encounters. OBJECTIVE: To explore the effect of communication-skills training on the process and outcome of care associated with patients' emotional distress. METHODS: A randomized, controlled field trial was conducted with 69 primary care physicians and 648 of their patients. Physicians were randomized to a no-training control group or one of two communication-skills training courses designed to help physicians address patients' emotional distress. The two training courses addressed communication through problem-defining skills or emotion-handling skills. All office visits of study physicians were audiotaped until five emotionally distressed and five nondistressed patients were enrolled based on patient response to the General Health Questionnaire. Physicians were also audiotaped interviewing a simulated patient to evaluate clinical proficiency. Telephone monitoring of distressed patients for utilization of medical services and General Health Questionnaire scores was conducted 2 weeks, 3 months, and 6 months after their audiotaped office visits. RESULTS: Audiotape analysis of actual and simulated patients showed that trained physicians used significantly more problem-defining and emotion-handling skills than did untrained physicians, without increasing the length of the visit. Trained physicians also reported more psychosocial problems, engaged in more strategies for managing emotional problems with actual patients, and scored higher in clinical proficiency with simulated patients. Patients of trained physicians reported reduction in emotional distress for as long as 6 months. CONCLUSIONS: Important changes in physicians' communication skills were evident after an 8-hour program. The training improved the process and outcome of care without lengthening the visits.

Adult↗

PubMed2005

Stochastic resonance of electrochemical aperiodic spike trains.

Aperiodic stochastic resonance in an electrochemical system with excitable dynamics is characterized in experiments and simulations. Two different spike trains, one with stochastic and the other with chaotic interspike intervals, are imposed on the system as subthreshold aperiodic signals. Information transmission is quantified by the cross correlation between the subthreshold input signal and the noise induced system response. A maximum is exhibited in the input-output correlation as a function of the noise amplitude. Numerical simulations with an electrochemical model are in excellent agreement with the experimental observations.

Copper Sulfate↗

PubMed1998

A comparative analysis of integrating visual representations with haptic displays.

As further advances in visual display technologies and force feedback devices are integrated in virtual systems, questions remain: What level of reality does the system provide to the user? Is the environment convincing enough to engage the user and to maximize transfer? Are the visual and haptic displays fully integrated to provide seamless operation in the simulated environment? Does the system provide not only the ability to navigate through a simulated environment, but also realistic interaction with instrumentation and structures? We report on our advances in developing a virtual simulation system for training in functional endoscopic sinus surgery (FESS). Specifically, we will present work on subject trials exploring the realism provided by integrated visual and haptic displays, and compare and contrast surface vs. volume representation for presenting realistic models of the anatomy for surgical interaction.

Computer Simulation↗

PubMedDate not supplied

Cross-training hospital nurses to reduce staffing costs.

There are advantages and disadvantages of cross-training hospital nurses. The financial benefit of reducing reliance on supplemental agency staff can be quantified. Cross-training policies can be compared. Simulation shows that the strategic cross-training principle of chaining performs particularly well. Practical formulas (that can be solved in a spreadsheet) are provided for quickly evaluating the economic performance of staffing and cross-training scenarios.

Absenteeism↗

PubMed2003

Virtual reality surgery: neurosurgery and the contemporary landscape.

OBJECTIVE: Virtual reality-simulated environments have been used for the training of personnel, most notably for military applications, for more than 35 years. The advantages conferred by being able to train novice personnel in a low- to no-risk simulated environment have long been appreciated by the medical community. The recent availability of affordable gigahertz-range microprocessors (once the exclusive domain of the Cray supercomputer) has made photorealistic graphical rendering and manipulation of virtual surgical substrates a reality. Concomitant advances in artificial intelligence systems and the portability of patient-specific magnetic resonance imaging, computed tomographic scanning, and angiographic image data presage the emergence of the surgical simulator as a modern surgical training adjunct. An overview of the status of surgical simulation with regard to its adaptability to current surgical training regimens is presented. METHODS: Extensive MEDLINE, Internet, and other database searches spanning the years 1960 to 2002 were conducted in an effort to delineate the status of simulated surgical environments. RESULTS: As would be expected, most articles addressing surgical simulation as their primary focus have been published in the past decade. A review of this literature demonstrates the broadest application in the field of endoscopic (and laparoscopic) procedures, most likely as a result of the reduced engineering burden with respect to incorporation of a haptic interface. CONCLUSION: The realization of ergonomically acceptable haptic interfaces remains elusive. Improvements in graphical rendering and the incorporation of artificial intelligence functions signal the certain emergence of surgical simulators as a viable supplement to the Halstedian method of surgical training.

Humans↗

PubMed2006

Bumblebees directly perceive variations in the spectral quality of illumination.

Individual bumblebees were tested on a task of walking along a test tunnel to collect sucrose solution in an initial training illumination condition that simulated natural daylight, and in two spectrally different illumination conditions. Compared to the training condition the bees took a significantly longer time to complete the task in conditions that simulated either an ultraviolet negative illumination environment, or an illumination environment that represented blue skylight. In a control condition, bees did not derive this cue from spectral information reflected from the dark background material. This result shows that bees can directly perceive spectral changes in illumination conditions, even in the context of a task that does not require colour processing. This potentially enables the visual system of bees to have prior knowledge about the spectral quality of illumination conditions in which they may forage. The findings are discussed in relation to both theoretical models and empirical evidence of colour constancy, and it is concluded that bees can use multiple mechanisms to solve the dilemma posed by having to find colour targets in the spectrally different illumination conditions that exist for insects visiting flowers.

Animals↗

PubMed2006

Learning phonetic categories by tracking movements.

We explore in this study how infants may derive phonetic categories from adult input that are highly variable. Neural networks in the form of self-organizing maps (SOMs; ) were used to simulate unsupervised learning of Mandarin tones. In Simulation 1, we trained the SOMs with syllable-sized continuous F(0) contours, produced by multiple speakers in connected speech, and with the corresponding velocity profiles (D1). No attempt was made to reduce the large amount of variability in the input or to add to the input any abstract features such as height and slope of the F(0) contours. In the testing phase, reasonably high categorization rate was achieved with F(0) profiles, but D1 profiles yielded almost perfect categorization of the four tones. Close inspection of the learned prototypical D1 profile clusters revealed that they had effectively eliminated surface variability and directly reflected articulatory movements toward the underlying targets of the four tones as proposed by . Additional simulations indicated that a further learning step was possible through which D1 prototypes with one-to-one correspondence to the tones were derived from the prototype clusters learned in Simulation 1. Implications of these findings for theories of language acquisition, speech perception and speech production are discussed.

Humans↗

PubMed2025

Chromatin structures from integrated AI and polymer physics model.

The physical organization of the genome in three-dimensional space regulates many biological processes, including gene expression and cell differentiation. Three-dimensional characterization of genome structure is critical to understanding these biological processes. Direct experimental measurements of genome structure are challenging; computational models of chromatin structure are therefore necessary. We develop an approach that combines a particle-based chromatin polymer model, molecular simulation, and machine learning to efficiently and accurately estimate chromatin structure from indirect measures of genome structure. More specifically, we introduce a new approach where the interaction parameters of the polymer model are extracted from experimental Hi-C data using a graph neural network (GNN). We train the GNN on simulated data from the underlying polymer model, avoiding the need for large quantities of experimental data. The resulting approach accurately estimates chromatin structures across all chromosomes and across several experimental cell lines despite being trained almost exclusively on simulated data. The proposed approach can be viewed as a general framework for combining physical modeling with machine learning, and it could be extended to integrate additional biological data modalities. Ultimately, we achieve accurate and high-throughput estimations of chromatin structure from Hi-C data, which will be necessary as experimental methodologies, such as single-cell Hi-C, improve.

Chromatin↗

PubMed2002

Open surgery simulation.

The design of simulators for surgical training and planning poses a great number of technical challenges. Therefore the focus of systems and algorithms was mostly on the more restricted minimal invasive surgery. This paper tackles the more general problem of open surgery and presents efficient solutions to several of the main difficulties. In addition to an improved collision detection scheme for computing interactions with even heavily moving tissue, a hierarchical system for the haptic rendering has been realized in order to reach the best performance of haptic feedback. A flexible way of modeling complex surgical tools out of simple basic components is proposed. In order to achieve a realistic and at the same time fast relaxation of the tissue, the approach of explicit finite elements has been substantially improved. We are able to demonstrate realistic simulations of interactive open surgery scenarios.

Algorithms↗

PubMedDate not supplied

The influence of fixational eye movements on the response of neurons in area MT of the macaque.

We analyzed the relationship between eye movements and neuronal responses recorded from area MT in alert monkeys trained to maintain visual fixation during the presentation of moving patterns. The monkeys made small saccades which moved the eyes with velocities that spanned the sensitivity range of MT neurons. The saccades evoked changes in the neuronal response that depended upon (1) the level of stimulus-evoked activity amidst which the saccade occurred and (2) the direction of the saccade relative to the preferred direction of the neuron. Most notably, saccades were able to suppress stimulus-evoked activity when they caused retinal image flow that opposed the neuron's preference and were able to elicit a response or enhance weak activity when they caused flow in the neuron's preferred direction. On average, the disturbance lasted 40 ms beginning about 40 ms following saccade onset. Using these parameters, we simulated synthetic spike trains from an imaginary pair of similarly tuned neurons and determined that the interneuronal correlation due to saccades should be negligible at all but the lowest ongoing firing rates. This conclusion was supported from our data by the observation that response variance for single MT spike trains was not measurably reduced during periods of stable gaze compared to periods when eye movement exceeded a stability criterion (0.1 deg during 0.5 s). While the intrusions caused by saccades are too short-lived and infrequent to account for the variability of MT neuronal response (counter to the finding in V1 of Gur et al., 1997), the clear directional signal that they carry in area MT suggests that motion perception is not blocked during saccades by suppression at early stages in the visual pathway.

Animals↗

PubMed1994

The HysteroTrainer, a simulator for diagnostic and operative hysteroscopy.

Hysteroscopy has become an integral part of operative gynecology, with rates of major complications of 1%. To avoid serious, even lethal, complications, an intensive, well-structured training program for practicing surgeons is necessary. In response to these educational requirements. The HysteroTrainer was developed to provide in vitro simulation training for diagnostic and operative hysteroscopy, including laser and high-frequency electrosurgery.

Cervix Uteri↗

PubMed1998

Simulated surgery in the summative assessment of general practice training: results of a trial in the Trent and Yorkshire regions.

BACKGROUND: General practice registrars are now required to undertake a summative assessment of their consulting skills. Simulated surgeries have been developed as an alternative to the existing method of assessing video-recorded consultations. AIM: To evaluate the simulated surgery assessment method, developed in the General Practice Postgraduate Education Department in Leicester, for use in assessing general practice consultation skills. METHOD: General practice registrars in Leicester performed two eight-patient simulated surgeries separated by four weeks. Assessment outcomes were compared to demonstrate the consistency of the method. Pilot surgeries in Yorkshire were videotaped, and then rated by video-raters trained for summative assessment. RESULTS: The method consistently identified those registrars who were competent and those who were not yet competent in consulting skills. It proved acceptable to candidate doctors and has fewer resource requirements for both examiners and candidates than other consulting skills assessment methods. CONCLUSION: The method developed in Leicester and successfully transferred to Yorkshire is feasible on a large scale, and offers an acceptable alternative to other consulting skills assessment methods. In this study it consistently identified competent from incompetent candidate doctors.

Clinical Competence↗

PubMed2006

Simulators and virtual reality in surgical education.

This article explores the pros and cons of virtual reality simulators, their abilities to train and assess surgical skills, and their potential future applications. Computer-based virtual reality simulators and more conventional box trainers are compared and contrasted. The virtual reality simulator provides objective assessment of surgical skills and immediate feedback further to enhance training. With this ability to provide standardized, unbiased assessment of surgical skills, the virtual reality trainer has the potential to be a tool for selecting, instructing, certifying, and recertifying gynecologists.

Clinical Competence↗

PubMed2006

Virtual reality ureteroscopy simulator as a valid tool for assessing endourological skills.

AIM: Virtual reality (VR) simulators are now commercially available for various surgical skills training. The Uro Mentor VR Ureteroscopy Simulator by Symbionix is one system that may revolutionize the way we assess and teach surgical residents. Surgical educators may no longer have to depend on the operating room as the sole venue for teaching residents technical skills. We validated performance on this new system with previously developed assessment tools and compared it to performance on a high fidelity ureteroscopy bench model. METHODS: Urology residents (n = 16) were assessed on their ability to perform cystoscopy, guidewire insertion, semirigid ureteroscopy and basket extraction of a distal ureteric stone on the VR simulator. A blinded examiner assessed subject performance using a checklist, global rating scale and a pass/fail rating. In addition, computer-generated parameters including time to complete task, scope and instrument trauma and the number of attempts to insert a guidewire were analysed. Performance on the VR simulator was compared to performance on a high fidelity ureteroscopy bench model. RESULTS: Senior residents (n = 8) scored significantly higher on their global rating scale (29.4 +/- 2.5 vs 20.8 +/- 0.9, P = 0.005), checklist (19.1 +/- 1.1 vs 15.2 +/- 0.9, P = 0.02), pass/fail rating (chi(2) = 7.3, P = 0.007) and required less time to complete the task (352.9 +/- 55.7 s vs 576.8 +/- 67.4 s., P = 0.02) than the junior residents (n = 8) on the VR simulator. Junior residents also had a significantly higher incidence of scope trauma (4 vs 0.6, P = 0.02). No significant differences were noted in instrument trauma and the number of attempts to insert the guidewire. Global rating scale performance on the VR simulator correlated well to performance on the high fidelity ureteroscopy bench model (r = 0.7, P = 0.002) as did time to complete task (r = 0.7, P = 0.004). CONCLUSIONS: The Uro Mentor VR Ureteroscopy Simulator is a useful tool in assessing resident endourological skills. Performance on the VR simulator is comparable to a validated high fidelity ureteroscopy bench model. Future studies will assess the utility of VR simulators in surgical skills training.

Adult↗