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PubMed1998

A cross-interval spike train analysis: the correlation between spike generation and temporal integration of doublets.

A stochastic spike train analysis technique is introduced to reveal the correlation between the firing of the next spike and the temporal integration period of two consecutive spikes (i.e., a doublet). Statistics of spike firing times between neurons are established to obtain the conditional probability of spike firing in relation to the integration period. The existence of a temporal integration period is deduced from the time interval between two consecutive spikes fired in a reference neuron as a precondition to the generation of the next spike in a compared neuron. This analysis can show whether the coupled spike firing in the compared neuron is correlated with the last or the second-to-last spike in the reference neuron. Analysis of simulated and experimentally recorded biological spike trains shows that the effects of excitatory and inhibitory temporal integration are extracted by this method without relying on any subthreshold potential recordings. The analysis also shows that, with temporal integration, a neuron driven by random firing patterns can produce fairly regular firing patterns under appropriate conditions. This regularity in firing can be enhanced by temporal integration of spikes in a chain of polysynaptically connected neurons. The bandpass filtering of spike firings by temporal integration is discussed. The results also reveal that signal transmission delays may be attributed not just to conduction and synaptic delays, but also to the delay time needed for temporal integration.

Action Potentials↗

PubMed1978

Task-specific simulator pretraining and in-flight stress of student pilots.

Student pilots (n = 20) were assigned to experimental and control groups. The experimental group received 80 min of high-fidelity, task-specific simulation prior to exposure to the initial power-on stall and spin recovery lesson unit in T-37 pilot training. Both experimental and control groups received orientation simulator experience not related to the aircraft spin series. Catecholamine excretion patterns indicated that the initial power-on stall and spin recovery lesson unit resulted in a pronounced stress response in both groups. A statistically significant difference in the norepinephrine/epinephrine ratio was found to exist between the experimental and control groups. It was concluded that task-specific simulator pretraining resulted in an altered stress response characterized by lower arousal and greater mental work than was evidenced in the control group.

Achievement↗

PubMed1999

ANNSyS: an Analog Neural Network Synthesis System.

A synthesis system based on a circuit simulator and a silicon assembler for analog neural networks to be implemented in MOS technology is presented. The system approximates on-chip training of the neural network under consideration and provides the best starting point for 'chip-in-the-loop training'. Behaviour of the analog neural network circuitry is modeled according to its SPICE simulations and those models are used in the initial training of the analog neural networks prior to the fine tuning stage. In this stage, the simulator has been combined with Madaline Rule III for approximating on chip training by software, thus minimizing the effects of circuit nonidealities on neural networks. The circuit simulator partitions the circuit into decoupled blocks which can be simulated separately, with the output of one block being the input for the next one. Finally, the silicon assembler generates the layout for the neural network by reading analog standard cells from a library. The system's performance has been demonstrated by several examples.

Journal Article↗

PubMed1995

Virtual reality in surgical education.

Virtual reality (VR) is an emerging technology that can teach surgeons new procedures and can determine their level of competence before they operate on patients. Also VR allows the trainee to return to the same procedure or task several times later as a refresher course. Laparoscopic surgery is a new operative technique which requires the surgeon to observe the operation on a video-monitor and requires the acquisition of new skills. VR simulation could duplicate the operative field and thereby enhance training and reduce the need for expensive animal training models. Our preliminary experience has shown that we have the technology to model tissues and laparoscopic instruments and to develop in real time a VR learning environment for surgeons. Another basic need is to measure competence. Surgical training is an apprenticeship requiring close supervision and 5-7 years of training. Technical competence is judged by the mentor and has always been subjective. If VR surgical simulators are to play an important role in the future, quantitative measurement of competence would have to be part of the system. Because surgical competence is "vague" and is characterized by such terms as "too long, too short" or "too close, too far," it is possible that the principles of fuzzy logic could be used to measure competence in a VR surgical simulator. Because a surgical procedure consists of a series of tasks and each task is a series of steps, we will plan to create two important tasks in a VR simulator and validate their use. These tasks consist of laparoscopic knot tying and laparoscopic suturing. Our hypothesis is that VR in combination with fuzzy logic can educate surgeons and determine when they are competent to perform these procedures on patients.

Clinical Competence↗

PubMed2003

Improved running economy in elite runners after 20 days of simulated moderate-altitude exposure.

To investigate the effect of altitude exposure on running economy (RE), 22 elite distance runners [maximal O(2) consumption (Vo(2)) 72.8 +/- 4.4 ml x kg(-1) x min(-1); training volume 128 +/- 27 km/wk], who were homogenous for maximal Vo(2) and training, were assigned to one of three groups: live high (simulated altitude of 2,000-3,100 m)-train low (LHTL; natural altitude of 600 m), live moderate-train moderate (LMTM; natural altitude of 1,500-2,000 m), or live low-train low (LLTL; natural altitude of 600 m) for a period of 20 days. RE was assessed during three submaximal treadmill runs at 14, 16, and 18 km/h before and at the completion of each intervention. Vo(2), minute ventilation (Ve), respiratory exchange ratio, heart rate, and blood lactate concentration were determined during the final 60 s of each run, whereas hemoglobin mass (Hb(mass)) was measured on a separate occasion. All testing was performed under normoxic conditions at approximately 600 m. Vo(2) (l/min) averaged across the three submaximal running speeds was 3.3% lower (P = 0.005) after LHTL compared with either LMTM or LLTL. Ve, respiratory exchange ratio, heart rate, and Hb(mass) were not significantly different after the three interventions. There was no evidence of an increase in lactate concentration after the LHTL intervention, suggesting that the lower aerobic cost of running was not attributable to an increased anaerobic energy contribution. Furthermore, the improved RE could not be explained by a decrease in Ve or by preferential use of carbohydrate as a metabolic substrate, nor was it related to any change in Hb(mass). We conclude that 20 days of LHTL at simulated altitude improved the RE of elite distance runners.

Acclimatization↗

PubMed1998

How occupational therapists teach older patients to use bathing and dressing devices in rehabilitation.

OBJECTIVE: This article describes the methods occupational therapists use to teach bathing and dressing device use to older patients in rehabilitation programs. The relationship of three patient characteristics to five aspects of assistive device instruction was examined. METHOD: The study sample included 86 patients and 19 occupational therapists who provided the assistive device training. Patients were 55 years of age or older and in rehabilitation for an orthopedic deficit, cerebrovascular accident, or lower limb amputation. Therapists recorded information on teaching methods, perceptions of patient knowledge, and expectations for future device use after each treatment session. RESULTS: Patients received an average of three dressing and two bathing devices for home use. Therapists devoted an average of two and a half sessions (10 min average duration) to teach dressing device use and an average of one session (9 min average duration) to teach bathing device use. Teaching occurred mostly in the clinic setting through oral instruction and demonstration. At discharge, patients who evaluated devices positively and were evaluated as having a positive affect were perceived by the therapists as "having greater knowledge of device use." More time was spent teaching those patients with lower Functional Independence Measure scores, less positive evaluations of devices, and lower affect scores. Family caregivers were involved in one or more dressing sessions for 26% of patients and one or more bathing sessions for 36% of patients. CONCLUSION: Assistive device training in rehabilitation centers consists largely of simulated sessions in the occupational therapy clinic, and patients in the study described the instruction they received as "satisfactory." More research is needed to study the long-term effectiveness of assistive device training after patients return home.

Activities of Daily Living↗

PubMed1996

Hardware prototypes of a Boolean neural network and the simulated annealing optimization method.

Boolean Neural Network is a neural network that operates with binary weight values of "1" and "0". Otherwise it is formally analogous to the Multilayer Perceptron (MLP). Simulated Annealing is a stochastic optimization methods that is suitable for performing nonlinear multivariable optimization tasks. Training a Boolean Neural Network is a well-suited problem to this algorithm. However, the Simulated Annealing method is computationally heavy, which makes the training procedure slow. The training speed can be improved by using custom designed hardware for the whole system including the optimization method and the neural network. Hardware prototypes of a Boolean Neural Network and the Simulated Annealing optimization method have been designed using discrete components. The Boolean Neural Network implementation is basically a dynamically configurable feedforward network of Boolean logic gates of two inputs. The Simulated Annealing implementation is a general purpose hardware tool for multivariable optimization tasks. Here it is applied to do supervised training of the Boolean Neural Network hardware.

Algorithms↗

PubMed2005

Validation of a flexible endoscopy simulator.

BACKGROUND: Virtual reality (VR) simulation is a rapidly proliferating adjunct of surgical training. Numerous devices have evolved as educational tools in a variety of fields. Whether these tools can be used for validation of physicians' skills has yet to be determined. The objective of this study was to determine whether the GI Mentor (Simbionix, Lod, Israel) flexible endoscopy simulator construct could distinguish experienced endoscopists from beginners. METHODS: Seventy-five surgical attendings, fellows, and residents were recruited for participation in the study. Two cohorts were used and these groups were selected from 2 separate scientific sessions. Participants completed a standardized questionnaire documenting their endoscopic training and experience. Physicians subsequently were designated as experienced or beginner after their endoscopic training and experience were evaluated. All participants completed 1 of 2 colonoscopic simulations. The GI Mentor objectively evaluated performance on the basis of programmed data points, including the time to reach the cecum, the percentage of mucosa visualized, the completed polypectomy rate, the percentage of time spent in clear view through the lumen, the percentage of time that the patient was in pain, and overall efficiency. RESULTS: In both simulations, experienced endoscopists were more efficient than beginners (.32%/s vs. .26%/s, P=.02; and .53%/s vs. .37%/s, P=.03) and achieved a greater polypectomy rate (78% vs. 43%, P=.03; and 87% vs. 48%, P=.01). Furthermore, experienced endoscopists visualized more of the colonic surface (86% vs. 82%, P=.02) and spent a greater proportion of the time in clear view of the lumen (55% vs. 47%, P=.05) than beginners completing the first simulation. In the second simulation, experienced participants reached the cecum more rapidly than beginners (175 vs. 262 s, P=.01). CONCLUSIONS: The G1 Mentor VR colonoscopy construct appears valid. Significant performance differences were shown between the experienced and beginner cohorts. The beginner participants in this study were all physicians with some degree of endoscopic experience. Therefore, the G1 Mentor distinguished endoscopists of varying experience and exposure. Further validation studies are needed to evaluate the breadth of programs inherent to this simulator and to determine whether it may be used in the future for qualification and certification purposes.

Clinical Competence↗

PubMed1995

Energy intake, physical activity and body weight: a simulation model.

In adults, body mass (BM) and its components fat-free mass (FFM) and fat mass (FM) are normally regulated at a constant level. Changes in FM and FFM are dependent on energy intake (EI) and energy expenditure (EE). The body defends itself against an imbalance between EI and EE by adjusting, within limits, the one to the other. When, at a given EI or EE, energy balance cannot be reached, FM and FFM will change, eventually resulting in an energy balance at a new value. A model is described which simulates changes in FM and FFM using EI and physical activity (PA) as input variables. EI can be set at a chosen value or calculated from dietary intake with a database on the net energy of foods. PA can be set at a chosen multiple of basal metabolic rate (BMR) or calculated from the activity budget with a database on the energy cost of activities in multiples of BMR. BMR is calculated from FFM and FM and, if necessary, FFM is calculated from BM, height, sex and age, using empirical equations. The model uses existing knowledge on the adaptation of energy expenditure (EE) to an imbalance between EI and EE, and to resulting changes in FM and FFM. Mobilization and storage of energy as FM and FFM are functions of the relative size of the deficit (EI/EE) and of the body composition. The model was validated with three recent studies measuring EE at a fixed EI during an interval with energy restriction, overfeeding and exercise training respectively. Discrepancies between observed and simulated changes in energy stores were within the measurement precision of EI, EE and body composition. Thus the consequences of a change in dietary intake or a change in physical activity on body weight and body composition can be simulated.

Adult↗

PubMed2004

Pyrolysis patterns of 5 close Corynebacterium species analyzed by artificial neural networks.

In the present study, an artificial neural network was trained with the Stuttgart Neural Networks Simulator, in order to identify Corynebacterium species by analyzing their pyrolysis patterns. An earlier study described the combination of pyrolysis, gas chromatography and atomic emission detection we used on whole cell bacteria. Carbon, sulfur and nitrogen were detected in the pyrolysis compounds. Pyrolysis patterns were obtained from 52 Corynebacterium strains belonging to 5 close species. These data were previously analyzed by Euclidean distances calculation followed by Unweighted Pair Group Method of Averages, a clustering method. With this early method, strains from 3 of the 5 species (C. xerosis, C. freneyi and C. amycolatum) were correctly characterized even if the 29 strains of C. amycolatum were grouped into 2 subgroups. Strains from the 2 remaining species (C. minutissimum and C. striatum) cannot be separated. To build an artificial neural network, able to discriminate the 5 previous species, the pyrolysis data of 42 selected strains were used as learning set and the 10 remaining strains as testing set. The chosen learning algorithm was Back-Propagation with Momentum. Parameters used to train a correct network are described here, and the results analyzed. The obtained artificial neural network has the following cone-shaped structure: 144 nodes in input, 25 and 9 nodes in 2 successive hidden layers, and then 5 outputs. It could classify all the strains in their species group. This network completes a chemotaxonomic method for Corynebacterium identification.

Algorithms↗

PubMed1998

Effects of training for two ball games on the saliva response of adrenocortical hormones to exercise in elite sportswomen.

In a group of 20 elite female handball or volleyball players, an evaluation was made of the response to a 4-month training period of cortisol, androstenedione and dehydroepiandrosterone in the saliva. At the beginning of the training programme (W1) and at the 7th (W7) and 16th weeks (W16), hormone concentrations were measured on awakening (8 a.m.; resting samples), and also before (t0) and at the end (t120) of a 2-h exercise session (simulated match) which took place at 6 p.m. The training programme increased the concentrations of adrenal androgens in the saliva at rest (P < 0.05) for both groups of subjects, with no change being noted in cortisol concentrations. In contrast, amongst the volleyball players, stressful stimuli produced by an increase in the amount of training did not affect adrenocortical metabolism during exercise. Indeed, a simulated volleyball match resulted in a decrease in salivary cortisol (P < 0.05) and androgen concentrations (P < 0.05) without regard for the week chosen for the test investigations. In contrast, a simulated handball match caused an increase in cortisol concentrations at W1 only (P < 0.05), with no change in the adrenal androgens concentration in any week of the training programme. The regulators of these hormones during a period of exercise and during the course of a training programme would seem to be different.

Adrenal Cortex Hormones↗

PubMed1994

[The Pulsatile Organ Perfusion - a chance to reduce animal experiments in minimally invasive surgery training]

The momentum brought about by the expansion in the field of minimally invasive surgery (MIS) and the endeavor of many surgeons to apply this operative technique, raises both quantitative as well as qualitative problems as far as the training in minimally invasive surgery is concerned. In the respective courses the training usually begins with synthetic dummies and/or animal organs in the simulation trainer. In the next - and already last - step before the clinical operation, the procedure is practiced on anesthetized animals. The wide gap between basic training and the animal experiment is filled by the Pulsatile Organ Perfusion (POP). POP simulates blood supply of organs or organsystems ideally and therefore it is the ideal method for completing training in laparoscopic and thoracoscopic techniques as this method would be used at any hospital or laboratory. The quality of simulating operations is excellent, the method is cost-effective and does not require the expense and infrastructure of the experimental animal laboratory. Furthermore the amount of animals required for advanced MIS-training will be greatly reduced.

Journal Article↗

PubMed2005

Role-playing for more realistic technical skills training.

Clinical skills are an important and necessary part of clinical competence. Simulation plays an important role in many fields of medical education. Although role-playing is common in communication training, there are no reports about the use of student role-plays in the training of technical clinical skills. This article describes an educational intervention with analysis of pre- and post-intervention self-selected student survey evaluations. After one term of skills training, a thorough evaluation showed that the skills-lab training did not seem very realistic nor was it very demanding for trainees. To create a more realistic training situation and to enhance students' involvement, case studies and role-plays with defined roles for students (i.e. intern, senior consultant) were introduced into half of the sessions. Results of the evaluation in the second term showed that sessions with role-playing were rated significantly higher than sessions without role-playing.

Adult↗

PubMed2004

The educational impact of bench model fidelity on the acquisition of technical skill: the use of clinically relevant outcome measures.

OBJECTIVE: To evaluate the impact of bench model fidelity on the acquisition of technical skill using clinically relevant outcome measures. METHODS: Fifty junior surgery residents participated in a 1-day microsurgical training course. Participants were randomized to 1 of 3 groups: 1) high-fidelity model training (live rat vas deferens; n = 21); 2) low-fidelity model training (silicone tubing; n = 19); or 3) didactic training alone (n = 10). Following training, all participants were assessed on the high- and low-fidelity bench models. Immediate outcome measures included procedure times, blinded, expert assessment of videotaped performance using checklists and global rating scales, anastomotic patency, suture placement precision, and final product ratings. Delayed outcome measures (obtained from the live rat vas deferens 30 days following training) included anastomotic patency, presence of a sperm granuloma, and the presence of sperm on microscopy. RESULTS: Following training, checklist (P < 0.001) and global rating scores (P < 0.001) on the bench model simulators were higher among subjects who received hands-on training, irrespective of model fidelity. Immediate anastomotic patency rates of the rat vas deferens were higher with increasing model fidelity training (P = 0.048). Delayed anastomotic patency rates were higher among subjects who received bench model training, irrespective of model fidelity (P = 0.02). Rates of sperm presence on microscopy were higher among subjects who received high-fidelity model training compared with subjects who received didactic training (P = 0.039) but did not differ among subjects in the high- and low-fidelity groups. CONCLUSIONS: Surgical skills training on low-fidelity bench models appears to be as effective as high-fidelity model training for the acquisition of technical skill among novice surgeons.

Adult↗

PubMed2005

Integrating a bovine rectal palpation simulator into an undergraduate veterinary curriculum.

There are problems associated with teaching bovine rectal palpation to undergraduate veterinary students. The students need opportunities to examine enough cows to develop the required skills, but increasing student numbers and limitations on access to cows have made this more and more difficult to achieve. A virtual reality-based teaching tool, the Bovine Rectal Palpation Simulator, has been developed as a supplement to existing training methods. The student palpates computer generated virtual models of the bovine reproductive tract while interacting with a haptic (touch feedback) device. During training sessions, the instructor follows the student's actions inside the virtual cow on the computer screen and gives instruction. A trial integration of the simulator into the fourth-year bovine reproduction course was undertaken at the University of Glasgow Veterinary School during the 2003/2004 academic year. Students were offered two training sessions, and feedback was gathered using questionnaires. In the first session, all students were taught a range of basic skills using a standardized teaching protocol. The second training session was customized to each student's learning needs and included practice in dealing with a range of on-farm scenarios. Student feedback indicated that the training had been useful for learning various aspects of bovine rectal palpation and provided information that helped in the further development of the simulator as a teaching tool.

Animals↗

PubMed2002

[Geometry of laparoscopy, telesurgery, training and telementoring].

Laparoscopic surgery in general is handicapped by the reduction of the range of motion from 6 to 4 degrees of freedom. This has a major impact on technically difficult procedures such as laparoscopic radical prostatectomy. Solutions for this problem include understanding the geometry of laparoscopy with sophisticated training programs, but also newly developed surgical robots, computer simulators, and telementoring. This article evaluates the value of these alternatives based on own experience and an analysis of the current literature. Our experience with robot-assisted surgery includes 244 laparoscopic radical prostatectomies using a voice-controlled camera arm (AESOP) and 6 telesurgical interventions with the da Vinci system. Additionally, experimental studies were performed focussing on the geometry of laparoscopy and new training concepts such as perfused pelvitrainers and computer simulation. Three-dimensional systems have not yet proved to be effective due to handling problems such as shutter glasses, video helmets, or reduced brightness. At present, there are only two robotic surgical systems (ZEUS, da Vinci) in clinical use for telesurgery, of which only the da Vinci provides stereovision and all 6 degrees of freedom (DOF). In the meantime, more than 100 laparoscopic radical prostatectomies have been performed with this system. However, there was no evidence of any advantages over the conventional laparoscopic approach. The ZEUS in combination with the telecommunication system SOKRATES is the only device that enables telemanipulation and telementoring over long distances (i.e., transatlantic). Robotic surgery represents a turning point in surgical research. However, broad use of robotic systems is limited mainly because of high investment and running costs. Whereas audiovisual telementoring will play a clear role in future training concepts, the need for telemanipulation or telesurgery has not yet been clarified.

Computer Simulation↗

PubMed2005

A parallel decision tree-based method for user authentication based on keystroke patterns.

We propose a Monte Carlo approach to attain sufficient training data, a splitting method to improve effectiveness, and a system composed of parallel decision trees (DTs) to authenticate users based on keystroke patterns. For each user, approximately 19 times as much simulated data was generated to complement the 387 vectors of raw data. The training set, including raw and simulated data, is split into four subsets. For each subset, wavelet transforms are performed to obtain a total of eight training subsets for each user. Eight DTs are thus trained using the eight subsets. A parallel DT is constructed for each user, which contains all eight DTs with a criterion for its output that it authenticates the user if at least three DTs do so; otherwise it rejects the user. Training and testing data were collected from 43 users who typed the exact same string of length 37 nine consecutive times to provide data for training purposes. The users typed the same string at various times over a period from November through December 2002 to provide test data. The average false reject rate was 9.62% and the average false accept rate was 0.88%.

Algorithms↗

PubMed1999

Small conductance potassium channels cause an activity-dependent spike frequency adaptation and make the transfer function of neurons logarithmic.

We made a computational model of a single neuron to study the effect of the small conductance (SK) Ca2+-dependent K+ channel on spike frequency adaptation. The model neuron comprised a Na+ conductance, a Ca2+ conductance, and two Ca2+-independent K+ conductances, as well as a small and a large (BK) Ca2+-activated K+ conductance, a Ca2+ pump, and mechanisms for Ca2+ buffering and diffusion. Sustained current injection that simulated synaptic input resulted in a train of action potentials (APs) which in the absence of the SK conductance showed very little adaptation with time. The transfer function of the neuron was nearly linear, i.e., both asymptotic spike rate as well as the intracellular free Ca2+ concentration ([Ca2+]i) were approximately linear functions of the input current. Adding an SK conductance with a steep nonlinear dependence on [Ca2+]i (. Pflügers Arch. 422:223-232; Köhler, Hirschberg, Bond, Kinzie, Marrion, Maylie, and Adelman. 1996. Science. 273:1709-1714) caused a marked time-dependent spike frequency adaptation and changed the transfer function of the neuron from linear to logarithmic. Moreover, the input range the neuron responded to with regular spiking increased by a factor of 2.2. These results can be explained by a shunt of the cell resistance caused by the activation of the SK conductance. It might turn out that the logarithmic relationships between the stimuli of some modalities (e.g., sound or light) and the perception of the stimulus intensity (Fechner's law) have a cellular basis in the involvement of SK conductances in the processing of these stimuli.

Action Potentials↗