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PubMed1988

Testing as a teaching tool.

More than four years ago, the authors initiated testing as a means of obtaining data for evaluating residents. The testing process has evolved now and is used for its teaching value and as a means of objective resident self-evaluation. Testing is designed to provide 10 cases an hour, with characteristics allowing a single diagnosis as a unique answer. No history is provided because a common topic and anatomic area provide a context for each examination. Answers are given during the examination after each question, and discussion follows. All answers are written, and answer sheets are collected. Attendance is high. Test scores are routinely lower than in other forms of evaluation. Testing integrates all aspects of radiology training from cognitive through deductive, simulates written consultations, and provides a means of self-evaluation through rapid feedback. Testing is a viable form of teaching that blends self-evaluation with faculty and peer feedback.

Educational Measurement↗

PubMed2006

The ergogenics of hypoxia training in athletes.

Hypoxia elicits hematopoiesis, which ultimately improves oxygen transport to peripheral tissues. In part because of this, altitude training has been used in the conditioning of elite endurance athletes for decades, despite equivocal evidence that such training benefits subsequent sea level performance. Recently, traditional live high-train high athletic conditioning has been implicated in a number of deleterious effects on training intensity, cardiac output, muscle composition, and fluid and metabolite balance--effects that largely offset hematopoietic benefits during sea level performance. Modified live high-train low conditioning regimens appear to capture the beneficial hematopoietic effects of hypoxic training while avoiding many of the deleterious effects of training at altitude. Because of the logistical and financial barriers to living high and training low, various methods to simulate hypoxia have been developed and studied. The data from these studies suggest a threshold requirement for hypoxic exposure to meaningfully augment hematopoiesis, and presumably improve athletic performance.

Adaptation, Physiological↗

PubMed1997

Late potential recognition by artificial neural networks.

Ventricular late potentials (LP's) are high-frequency low-amplitude signals obtained from signal-averaged electrocardiograms (ECG's) [SAECG's]. LP's are useful in identifying patients prone to ventricular tachycardia (VT), spontaneous or inducible during electrophysiology testing. A combination of self-organizing and supervised artificial neural network (ANN) models was developed to identify patients with a positive electrophysiology (PEP) test for inducible ventricular tachycardia from patients with a negative electrophysiology (NEP) test using LP's. We have added morphology information of vector magnitude waveform to original set of three time-domain features of LP's, which are total QRS duration (TQRSD), high-frequency low-amplitude signal duration (HFLAD), and root-mean-square voltage (RMSV). Pattern recognition results from an ANN model with this combination feature set are superior to the results from Bayesian classification model based on conventional three time-domain features of SAECG. In order to increase the robustness of the recognition, a filtered QRS offset point is randomly shifted +/- 8 ms to form a fuzzy training set, which was to simulate the possible error in detecting QRS offset point of filtered SAECG. We also found that nonlinear transformation through the hidden layer of developed ANN model could increase Euclidean distance between PEP and NEP patterns.

Algorithms↗

PubMed2006

Tracking tremor frequency in spike trains using the extended Kalman smoother.

Tremor is one of the most disabling symptoms in patients with many movement disorders including Parkinson's disease (PD) and essential tremor (ET). Neural tremor manifests itself as a quasi-periodic fluctuation of the firing rate. We describe a frequency tracking method based on the extended Kalman smoother (EKS) to estimate the instantaneous tremor frequency (ITF) exhibited in binary spike trains detected from neural recordings. Simulation results demonstrate that the EKS frequency tracker can estimate the ITF accurately, even though the signal of interest is not sinusoidal and the noise is not Gaussian. The EKS frequency tracker can obtain a normalized mean squared error (NMSE) as low as 0.1 and performs much better than the conventional approach based on the Hilbert transform.

Action Potentials↗

PubMed1989

Range estimation by echolocation in the bat Eptesicus fuscus: trading of phase versus time cues.

Bats of the species Eptesicus fuscus have been trained to discriminate a stationary simulated target from a target with a virtual distance that jitters from sound to sound. Similar to Simmons [Science 207, 1336-1338 (1979)], a jitter-detection threshold below 1 microsecond was found. However, Simmons' decreased performance at a time delay jitter of 30 microseconds could not be replicated, a critical feature used to postulate the idea that bats employ a coherent cross-correlation receiver for ranging. Such a receiver uses all phase information in the signal for delay estimation and therefore will be biased by phase manipulations. To test for such a bias, a phase jitter of +/- 45 degrees and a time jitter in the echo were overlaid. It was not found that there was a combination of both where their effects canceled. Full phase information is thus not used in delay estimation. However, bats were able to detect a pure phase jitter, e.g., polarity inversion of the signal. Bats could also detect phase jitter in the presence of randomized time jitter and vice versa. Phase jitter and time jitter, therefore, are separable features for a bat. The underlying physiological mechanism is not clear.

Amplifiers, Electronic↗

PubMed1994

Model reference direct adaptive control of nonlinear plants using neural networks.

A learning scheme for multilayer feedforward neural networks used as direct adaptive controllers of nonlinear plants is suggested. This scheme is a supervised steepest descent one that does not require backpropagation of the error. Using a neural network controller trained with this method does not require the identification stage and this makes it superior to the other methodologies. Methods for using neural networks in plant control suggested in the literature are discussed and compared with the proposed system. The structure of the network and the training method used are explained. Simulations based on model reference control of some nonlinear plants show satisfactory performance.

Computer Simulation↗

PubMed1982

Neural representation of target distance in auditory cortex of the echolocating bat Myotis lucifugus.

1. Single- and multiunit recordings were obtained from neurons in the auditory cortex of the echolocating bat Myotis lucifugus, while trains of stimuli designed to simulate the bat's frequency-modulated (FM) orientation pulse and its returning echo were delivered. It was found that many neurons in the cortex responded selectively to pulse-echo pairs only if the time delay separating the artificial pulse and the echo was within a certain range. This response property is called "delay-dependent facilitation." Since echolating bats are known to utilize echo-delay information for the determination of target distance, it is postulated that these neurons are involved in the process of distance perception. 2. Two types of delay-sensitive neurons were characterized on the basis of their response patterns. P-type units had short maximum response delays, narrow delay response functions, and response latencies for pulse-echo pairs that were similar to their response latencies for single loud FM pulses. E-type units had longer maximum response delays, wide delay response functions, and pulse-echo pair response latencies that were time-locked to the echo. Another important difference between these two classes was that changes in the amplitude of the artificial echo caused systematic changes in the delay response of E-type units but not of P-type units. 3. The sharpness and stability of the delay response functions of P-type units suggested that they may encode target distance by responding at discrete echo delays. In contrast, delay tuning may not be an unambiguous determinant of echo delay in E-type units. Here, the most consistent and reliable response parameter for echo delay is the time at which the responses occurred. This suggested that echo delay could be encoded by the temporal pattern of responses in E-type units in relation to the responses evoked by the outgoing orientation cry. The different range of delay of delay sensitivity of P-type and E-type units indicates that these two mechanisms could be operating at different ranges of target distance. 4. P-type and E-type responses may not be due to different populations of neurons but to different response properties of the same population under different conditions. Evidence for this proposition was obtained by showing that in some recordings, decreases in the amplitude of the artificial pulse caused a switch in response from a long best delay, E-type response to a short best delay, P-type response. This suggested that the delay sensitivity of cortical neurons could be under the bat's control based on the intensity of its pulse emissions.

Animals↗

PubMed1993

Coincidence detection by binaural neurons in the chick brain stem.

1. Neurons in nucleus laminaris (NL) of birds are the first to receive binaural information and are presumed to play a role in encoding interaural time differences (ITDs). We studied extracellular single-unit responses of NL neurons in slices of the auditory brain stem of the chick. The afferents to NL were activated by electrical stimulation of nucleus magnocellularis (NM) or the auditory nerve. Changes in responses were measured as the delay between trains of bilateral stimuli (the simulated interaural time difference or S-ITD, n = 26) was varied and as the interstimulus interval and stimulus amplitude were varied (n = 61). 2. The probability of an action potential and the action-potential latency varied as a function of interstimulus interval. Most NL neurons showed a greater response probability and a shorter response latency to an interstimulus interval between 2.5 and 3.5 ms. The interstimulus interval that produced the minimum response latency was slightly longer than the interval that produced the maximum response probability. In contrast, NM neurons (n = 4) showed no preferred rate, instead, the probability of firing increased as the interstimulus interval increased. 3. Responses to bilateral stimulation showed that NL neurons can act as coincidence detectors. NL neurons responded most reliably when activated simultaneously by their two inputs and, at favorable S-ITDs, two subthreshold inputs combined to produce an action potential. 4. NL neurons also exhibited inhibition during bilateral stimulation. At unfavorable S-ITDs a subthreshold input combined with a suprathreshold input produced fewer action potentials than evoked by the suprathreshold input alone. 5. The latency of the bilateral response varied as a function of S-ITD. At S-ITDs near coincidence the latency of the bilateral response was shorter than the latency of either of the unilateral responses. Away from coincidence, the latency of the bilateral response was largely determined by the latency of the stronger unilateral response. When the unilateral responses were of similar strength, the earlier stimulus determined the latency of the bilateral response. 6. The range of S-ITDs producing a maximal response varied as a function of stimulus strength but was never less than approximately 300 microseconds. This is greater than the maximum possible ITD of sound calculated for the chick's head size. From these data we hypothesize that, in the chick, single units cannot uniquely encode ITDs, but rather ITDs may be coded by the proportion of maximally firing cells along an isofrequency band in NL.

Animals↗

PubMed1995

Comparison of direct and indirect calculations of laryngeal airway resistance in various voicing conditions.

Calculation of laryngeal airway resistance using intraoral pressure divided by airflow has become a widely accepted clinical tool. The estimation is based largely on theoretical assumptions, particularly regarding the relationship between intraoral and subglottal pressure. To determine the estimate's validity, direct measures of airflow and subglottal, intraoral and pharyngeal pressures were obtained for four men and four women. Subjects produced normal, loud, soft and simulated breathy and strained syllable trains. Comparison of direct and indirect calculations of laryngeal airway resistance revealed generally good correspondence, particularly for [pi] syllables, although the estimate's accuracy varied among individual subjects. Some interpretive caution is warranted for the extremes of laryngeal airway resistance, with resistance likely to be underestimated in the strained condition, and overestimated in the breathy condition.

Adult↗

PubMed1999

Hierarchical decomposition of laparoscopic procedures.

The purpose of this report is to outline the hierarchical decomposition of surgical procedures, from surgical steps through tasks and subtasks to tool motions, and highlight implications for surgical training systems. Three common laparoscopic procedures were analysed: cholecystectomy, inguinal hernia repair, and Nissen fundoplication. In laparoscopic training workshops and operating rooms, our observational research included split screen videotaping of both the endoscopic view and our video camera's view of the primary surgeon. Videotapes were extensively annotated and analysed to yield timelines of each procedure, with component surgical steps, substeps, tasks, and subtasks duration as a function of procedure. The hierarchical decomposition of surgical procedures provides a framework for structuring a systematic approach to training, in the real and simulated environment. An example comparing variations in the fundoplication procedure is presented. Our results also have important implications for the design and assessment of new technology and intelligent tools in endoscopic surgery.

Cholecystectomy, Laparoscopic↗

PubMed1975

Selection of artificial gravity by animals during suborbital rocket flights.

White rats selected preferred artificial gravity levels by locomotion in centrifuges consisting of two runways mounted in the nose of sounding rockets. Roll rate of the Aerobee 150A rocket was designed to produce an angular velocity of 45 r.p.m. during 5 min of free-fall, providing a gravity range range from 0.3 to 1.5 G depending on a subject's runway position. One animal was released at the high and one at the low gravity position in each flight. Animal positions were continuously recorded. Flight subjects were selected from about 100 trained animals adapted to the simulated launch environment for several months. In two flights excessive rollrates produced gravity ranges above the designed limits. In two other flights the desired range was produced. Locomotion patterns during these flights were similar. All four animals explored the entire available G-range. One rat settled at 0.4 G after 2 min; the others crossed the 1-G location in progressively narrower excursions and were near earth gravity at the end of the test period. Data were more varible than in laboratory tests above 1 G and the observation periods were necessarily few and short. Tentatively, however, the data suggest that normal earth-reared rats select earth gravity when available magnitudes include values above and below 1 B. Modification of gravity preference by prolonged exposure to higher or lower levels remains a possibility.

Animals↗

PubMed2001

Adaptive eye movements induced by cross-axis pursuit--vestibular interactions in trained monkeys.

We showed previously that smooth pursuit training combined with whole-body rotation in the orthogonal plane induces adaptive cross-axis vestibulo-ocular reflex (VOR). To gain an insight into the possible pathways and the nature of error signals for cross-axis VOR adaptation, we examined further properties of adaptive responses. In the first series, we trained monkeys for vertical pursuit during sinusoidal yaw rotation at 0.5 Hz (+/- 10 degrees) by presenting a target spot either in phase with, or with phase shifts (lead or lag) of 90 degrees to, the chair for 1 h. After training, sinusoidal or trapezoidal yaw rotation was tested in complete darkness without a target. Different training conditions resulted in different amounts of phase shift in cross-axis VOR. Trapezoidal yaw rotation (peak acceleration approximately 780 degrees/s2) revealed further differences in the direction, latency and time course of the adaptive responses depending on the conditions of the pursuit task. At least two (fast and slow) components with different latencies were induced in the cross-axis VOR by trapezoidal rotation after in-phase and phase-shift training. Adaptive responses were accurately simulated by the weighted sum of these two components. In the second series, we examined the effects of sequentially flashed (10 microseconds) targets in the horizontal plane during pitch rotation. The monkeys learned to track such targets by smooth pursuit, and cross-axis VOR was also induced after such apparent motion stimuli without retinal slip of the target image. These results indicate the importance of eye velocity for cross-axis VOR and suggest that this adaptation occurs most probably in the smooth pursuit pathways.

Adaptation, Physiological↗

PubMed1999

[Comparison between motion sickness induced by reversed vision and that by parallel swing].

OBJECTIVE: To make clear the characteristics of motion sickness induced by reversed vision and to see whether it can be used in motion sickness experiments. METHODS: 10 healthy young men experienced walking tests wearing up-down or left-right reversing prisms, and parallel swing test on different days with intervals of 5-7d. Ataxia and motion sickness symptoms induced by walking wearing reversing prisms and those by parallel swing were observed. The reversed vision tolerance index (RVTI) and linear acceleration tolerance index (LATI) were calculated by an empirical formula. RESULTS: Both types of reversing prisms can induce obvious ataxia and motion sickness symptoms. The ataxia is correlative (P<0.05) with the susceptibility to motion sickness. In comparison with symptoms of swing motion sickness, the symptoms of reversed vision motion sickness are not too serious and appear slowly. There are correlativities (P< 0.01) between the susceptibility to motion sickness induced by up-down and left-right reversing prisms. The susceptibilities to motion sickness induced by reversing prisms are not correlative completely with that by swing. CONCLUSION: Reversed vision test is simple and easy and can be used for simulating space motion sickness or training of adaptation to sensory conflict on the ground.

Acceleration↗

PubMed2000

[Determination of five component infrared spectra system with artificial neural network].

This article demonstrates the application of artificial neural network in multi-component analysis. Parameters were obtained after the BP network was trained with large amount of simulated data. Five organic toxins whose FTIR spectra are strongly overlapped were used to make the multi-component system. The relative standard deviation(RSD%), the percent standard error of prediction samples(SEP%) and the percent standard error of calibration samples(SEC%) were used for evaluating the ability of the neural network.

Air Pollutants↗

PubMed1992

Effects of varying recovery periods on muscle enzymes, soreness, and performance in baseball pitchers.

In this study we examined the effects of varied recovery time on serum creatine kinase (CK), serum lactate dehydrogenase (LDH), muscle soreness, and pitch velocity in baseball pitchers. Ten males who had pitching experience participated in the study. After an 18-day training period, subjects pitched three simulated games. Game A and Game B were separated by four days of rest, while Game B and Game C were separated by two days of rest. CK, LDH, and muscle soreness were evaluated at the following times: before and immediately after exercise, and six, 24, 48, and 72 hours after exercise. Muscle performance was evaluated by measuring pitch velocity during the games. The CK level was elevated after each game (Game A - 249 U/l; Game B - 243 U/l; and Game C - 240 U/l); then it dropped toward baseline (p</=0.01). CK post-exercise values were not different among games A, B, and C. LDH displayed a response similar to CK; however, there was a reduction over the span of the games (p</=0.05). Muscle soreness was significantly elevated immediately after exercise (p</=0.01) compared to all other measurement times. Pitch velocity was not different among games A, B, and C. Results indicate that muscle damage, as evidenced by CK release, occurs in response to baseball pitching. However CK values, muscle soreness, and pitch velocity are not significantly affected by changes in the amount of recovery time typically scheduled between games.

Journal Article↗

PubMed1987

'Athlete's heart' in prepubertal children.

Bradycardia, cardiomegaly, heart murmurs, and ECG changes are typically observed in adult endurance athletes, but frequency of such changes among children involved in sports training is unclear. Pediatricians need to be aware of whether these features of the "athlete's heart" occur in their patients, because such features may mimic those of cardiac disease. Fourteen prepubertal competitive male swimmers were evaluated by physical examination, ECG and echocardiogram, and findings were compared to those of a group of active but nontrained control boys. Lower resting heart rates and echocardiographic manifestations of chronic left ventricular volume overload were observed among the swimmers. These changes were not manifest on physical examination, however, and no significant ECG alterations were identified among the athletes. These findings indicate that, although features of the athlete's heart are present in children involved in endurance training, seldom will these findings simulate heart disease or be apparent on routine clinical examination.

Adaptation, Physiological↗

PubMed1995

HPCC and the National Information Infrastructure: an overview.

The National Information Infrastructure (NII) or "information superhighway" is a high-priority federal initiative to combine communications networks, computers, databases, and consumer electronics to deliver information services to all U.S. citizens. The NII will be used to improve government and social services while cutting administrative costs. Operated by the private sector, the NII will rely on advanced technologies developed under the direction of the federal High Performance Computing and Communications (HPCC) Program. These include computing systems capable of performing trillions of operations (teraops) per second and networks capable of transmitting billions of bits (gigabits) per second. Among other activities, the HPCC Program supports the national supercomputer research centers, the federal portion of the Internet, and the development of interface software, such as Mosaic, that facilitates access to network information services. Health care has been identified as a critical demonstration area for HPCC technology and an important application area for the NII. As an HPCC participant, the National Library of Medicine (NLM) assists hospitals and medical centers to connect to the Internet through projects directed by the Regional Medical Libraries and through an Internet Connections Program cosponsored by the National Science Foundation. In addition to using the Internet to provide enhanced access to its own information services, NLM sponsors health-related applications of HPCC technology. Examples include the "Visible Human" project and recently awarded contracts for test-bed networks to share patient data and medical images, telemedicine projects to provide consultation and medical care to patients in rural areas, and advanced computer simulations of human anatomy for training in "virtual surgery."

Computer Communication Networks↗

PubMed1995

EPIZOO: software for veterinary epidemiology training and problem-solving.

Described is a computer software package, EPIZOO, which has been developed specifically for undergraduate and postgraduate education, self-training, problem-solving, and simulation studies in veterinary epidemiology. The program is based on action-oriented animal population health/disease analyses and programming. EPIZOO runs on IBM-compatible personal computers and can be used for any animal population diseases, including those transmissible to man. The software comprises an integral system of selected indicators contained in twelve modules, with about 200 widely applicable methods used in epizootiology. It is user-friendly and includes general methods related to the following: animal population characteristics of health/disease importance; analysis of animal population health and disease situations, structures, dynamics, diagnoses, and consequences; preparation, cost, and evaluation of animal population health programmes; and selected statistical techniques.

Animal Diseases↗