Fake worlds offer real medicine: virtual reality finding a role in treatment and training.
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Computer Simulation↗
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Application of probabilistic neural network analysis to a disease with complex inheritance: the GAW11 simulated data.
A probabilistic neural network analysis was applied to the simulated GAW11 data. Six replicates drawn at random from one of the simulated populations were used to generate training and test vectors for pairs of siblings. The vectors incorporated two environmental indicators as well as identical-by-descent allele sharing scores from each of 300 genetic markers. The performance of a 'naïve' probabilistic neural network (PNN) was fair. However, by combining a traditional linkage analysis with a PNN which incorporated gene x environment interaction, the performance was considerably enhanced.
Alleles↗
The effect of skill training on functional abilities of nursing home residents with dementia.
The purpose of this experimental study was to compare the effects of skill training, a traditional stimulation approach, and regular care (control group) on the ability to perform the basic activities of daily living of nursing home residents with dementia. Sixty-three subjects were randomly selected and randomly assigned to the three groups. Ability to perform the basic activities of daily living (ADLs) and progress toward meeting individually set ADL-related goals were measured. Significant differences were found in two of the three measures used. In general, the greatest improvement was found in the skill training group, modest improvement in the simulation group, and decline in the control group.
Activities of Daily Living↗
Action potentials that mimic fibrillation activate sodium current.
Ventricular fibrillation (VF) has brief action potentials (50-70 ms) with short diastolic intervals (10-30 ms). Under these conditions ion channel activity may be grossly different to normal sinus rhythm (NSR). In particular, sodium channel activation may not contribute to the generation and propagation of action potentials during VF. This study determined if sodium channels can be activated when action potentials mimic VF. Isolated chick ventricular myocytes (n=7) were voltage-clamped to quantitate fast inward sodium current. The voltage clamp protocol simulated VF with a 10 pulse train at 10 Hz (100 ms cycle length (CL)) and depolarization interval (action potential duration) ranging from 90 to 20 ms. After each train a test pulse was delivered from holding (-80 mV) in 10-ms steps. The train preceded each step pulse. Peak sodium current for control and each VF protocol occurred at a membrane potential (V(m)) of -10 mV. Sodium current was evident during brief resting intervals as short as 20 ms, albeit 10-20% of baseline. Resting intervals less than 60 ms shifted the sodium conductance activation curve from Vm(0.5)-30 mV to -22 mV membrane potential. Similar findings occurred when resting potential was at -65 mV, although there was less sodium current with all tested protocols. There was significantly less inactivation of sodium current when the prepulse was shorter (100 v 1000 ms). There was approximately 20% greater sodium current when the test pulse followed a short v long depolarized (>-80 mV) prepulse. Although the longer depolarization pulses produce approximately 20% greater sodium current at membrane potentials more negative than -80 mV. Lastly the time for half recovery of sodium current from activation was significantly less when the inactivating prepulse was short v long (45.9+/-9 v 118+/-20 ms, P<0.05). In conclusion, sodium current is evident when the diastolic rest interval is as brief as 10-20 ms. Rest interval, length of membrane depolarization and membrane potential interact to affect sodium channel activation, inactivation and recovery from inactivation. These data demonstrate that the brief action potentials at more depolarized membrane potentials seen during VF allow for inward sodium current upon depolarization, less sodium channel inactivation, and a faster recovery from inactivation, thereby compensating for a short diastolic rest interval. Therefore, it is likely that the inward sodium channel contributes to wave front propagation during ventricular fibrillation.
Action Potentials↗
Assessment of mental workload with task-irrelevant auditory probes.
A study was performed to examine the utility of an ERP-based irrelevant probe technique for the assessment of variations in mental workload. Ten highly trained Navy radar operators performed a simulated radar-monitoring task which varied in the density and type of targets to be detected and identified. This task was performed in the presence of a series of irrelevant auditory probes which the radar operators were instructed to ignore. Prior to performing the radar-monitoring task the subjects performed a block of auditory detection trials in which they were asked to respond to the occurrence of one of two low probability tones and ignore the other low probability tone along with a higher probability standard tone. ERPs were recorded from the occurrence of the tones in both the baseline and low and high workload radar-monitoring conditions. The amplitude of the N100, N200, and early and late mismatch negativity (MMN) components decreased from the baseline to the low load radar-monitoring task and again with an increase in the difficulty of the radar-monitoring task. P300 amplitude was sensitive only to the introduction of the radar-monitoring task. These results are interpreted with respect to the phenomenon of attentional capture and suggest that the ERP-based irrelevant-probe technique might prove an effective method for the nonintrusive evaluation of increases in mental workload in complex tasks.
Adult↗
A randomized trial of a decisional aid for mental capacity assessments.
The objective of this study was to evaluate the clinical utility of a decisional aid for mental capacity assessments which was developed using a group judgment methodology. This was carried out by a randomized, controlled trial. The subjects comprised 64 University of Toronto psychiatry residents in postgraduate years 1 through 4. Residents were randomized to carry out mental capacity assessments on simulated cases with, or without, the use of the decisional aid. The main outcome measure was the extent of agreement between the mental capacity determinations of residents and those of experts. There was no difference between the intervention and control groups with respect to the overall mean level of agreement with experts (0.87 vs 0.86, p = 0.88; 95% confidence interval for the difference between the study groups, -0.07 to +0.08). A logistic regression analysis, which adjusted for imbalances between the groups, also revealed no difference between the groups in their agreement with experts. The mean time per competency assessment was significantly longer in the intervention group (19.1 vs 10.8 min; p < 0.001). It was concluded that the decisional aid did not improve the ability of the psychiatry residents to make mental capacity assessments on simulated cases. Despite relatively limited formal training, the psychiatry residents had a high level of agreement with experts.
Adult↗
Informed consent procedures: an experimental test using a virtual character in a dialog systems training application.
Researchers are generally trained to administer informed consent by studying approved guidelines, but still can fail to satisfactorily answer questions from potential participants. An application using a virtual character allowed novice participants to practice administering informed consent. This character was designed to behave as a potential participant for a study and asked many of the questions research participants typically ask, such as queries about the study itself, the sponsor, timing, selection procedures, confidentiality, voluntariness, benefits and risks, and contact information. The user responded to the character's queries as if speaking with a true potential research participant. The application was effective even after only brief usage. In a laboratory experiment, novice participants who practiced with the virtual character were later more effective in conducting informed consent interviews with a human interviewee than those who were trained only with written materials. Thus, simulated learning-by-doing improved informed consent skills. Implications for related health dialog applications are discussed.
Biomedical Research↗
Variability in the clinical skills of residents entering training programs in surgery.
BACKGROUND: Residents may have significant differences in clinical skills at the start of their surgical training. The purpose of this study was to investigate the variability in these skills by using an objective structured clinical examination. METHODS: A needs assessment was performed, and an objective structured clinical examination composed of 10, two-part stations was developed. Standardized patients (SPs) were trained, validated, and used as both simulated patients and evaluators to assess history taking, physical examination, and interpersonal skills of 10 first-year surgical residents. Structured patient notes (PNs) written by residents after the SP encounters were used to assess history and physical examination documentation skills. Data from one station were not used because more than 25% of the SP ratings were missing. RESULTS: The alpha-reliability was 0.78 for SP ratings, 0.91 for PN scores, and 0.91 for the combined scores. ANOVA revealed significant variation in individual residents' clinical skills as assessed by SPs (F = 4.56, p < 0.01), PNs (F = 11.09, p < 0.001), or both (F = 10.9, p < 0.001). Paired t tests showed that residents scored significantly higher on history taking than on physical examination and attained significantly lower scores on documentation as compared with performance of both history and physical examination (p < 0.001 for each comparison). CONCLUSIONS: The results showed significant variability in clinical skills of the group of residents and yielded detailed information on the performance of each resident. The data were shared with individual residents and are being used to make changes in the educational activities of the program.
Clinical Competence↗
Phonology and syntax in specific language impairment: evidence from a connectionist model.
Difficulties in resolving pronominal anaphora have been taken as evidence that Specific Language Impairment (SLI) involves a grammar-specific impairment. The present study explores an alternative view, that grammatical deficits in SLI are sequelae of impaired speech perception. This perceptual deficit specifically affects the use of phonological information in working memory, which in turn leads to poorer than expected syntactic comprehension. This hypothesis was explored using a connectionist model of sentence processing that learned to map sequences of words to their meanings. Anaphoric resolution was represented in this model by recognizing the semantics of the correct antecedent when a bound pronoun was input. When the model was trained on distorted phonological inputs-simulating a perceptual deficit-it exhibited marked difficulty resolving bound anaphors. However, many other aspects of sentence comprehension were intact; most importantly, the model could still resolve pronouns using gender information. In addition, the model's deficit was graded rather than categorical, as it was able to resolve pronouns in some sentences, but not in others. These results are consistent with behavioral data concerning syntactic deficits in SLI. The model provides a causal demonstration of how a perceptual deficit could give rise to grammatical deficits in SLI.
Child↗
A pruning method for the recursive least squared algorithm.
The recursive least squared (RLS) algorithm is an effective online training method for neural networks. However, its conjunctions with weight decay and pruning have not been well studied. This paper elucidates how generalization ability can be improved by selecting an appropriate initial value of the error covariance matrix in the RLS algorithm. Moreover, how the pruning of neural networks can be benefited by using the final value of the error covariance matrix will also be investigated. Our study found that the RLS algorithm is implicitly a weight decay method, where the weight decay effect is controlled by the initial value of the error covariance matrix; and that the inverse of the error covariance matrix is approximately equal to the Hessian matrix of the network being trained. We propose that neural networks are first trained by the RLS algorithm and then some unimportant weights are removed based on the approximate Hessian matrix. Simulation results show that our approach is an effective training and pruning method for neural networks.
Algorithms↗
The effect of experimental design on the modeling of a tablet coating formulation using artificial neural networks.
The aim of this study was to investigate the effect of experimental design strategy on the modeling of a film coating formulation by artificial neural networks (ANNs). Box-Behnken, central composite and pseudo-random designs of 102, 90 and 100 simulated records, respectively were used to train a multilayer perceptron (MLP) ANN comprising six input and two output nodes separated by a single hidden layer of five nodes. Network over-training was limited by using a test set of 40 pseudo-randomly distributed records. The models were validated using a set of 60 pseudo-randomly distributed records. Crack velocity was highly curved with respect to pigment particle size and size distribution. Similarly, film opacity was highly curved in response to pigment concentration and film thickness. The Box-Behnken and central composite designs generated models that were unable to predict crack velocity and showed extensive bias in prediction of film opacity. The pseudo-random design was unable to predict crack velocity of the test data set but yielded acceptable predictions for the validation set. Film opacity was well predicted by the pseudo-random design model. The poor predictive ability of the Box-Behnken and central composite models was attributed to poor interpolation of the high curvature of the response surfaces. In contrast, the pseudo-random design mapped the interior of the design space allowing improved interpolation and predictive ability. It is concluded that Box-Behnken and central composite experimental designs are inappropriate for ANN modeling of highly curved responses and that extensive internal mapping of the design space is essential to generate predictive ANN models.
Drug Design↗
A model for neurologic sources of aperiodicity in vocal fold vibration.
The time course of a force twitch in the thyroarytenoid muscle is modeled, and trains of twitches are summed to simulate force tetani. By incorporating means and standard deviations of motoneuron firing rates, and by applying random phase relationships between simulated motor units, a quantitative model of the ripple of vocal fold tension is obtained. From this ripple, perturbations in fundamental frequency are calculated as a function of the number of motor units in the muscle, the mean and standard deviation of the firing rate of dominant motoneurons, and the variability in the size (twitch amplitude) of the motor units. Predicted perturbations range between 0.2% and 1.2%, depending on the choice of parameters. Perturbation decreases with the number of motor units and with increased mean firing rate, but increases with the variability in motor unit size and with variability in the firing rate. Techniques are discussed by which neurologic jitter might be isolated from other sources of irregularity in vocal fold vibration.
Action Potentials↗
Assuring the quality of high-stakes undergraduate assessments of clinical competence.
In the UK, and in many Commonwealth countries, a university degree is accepted by registration bodies as an indication of competence to practice as a PRHO or intern. Concerns have been raised that the quality of university examinations may not always be sufficient for such high-stakes decision-making. Assessments of clinical competence are subject to many potential sources of error. The search for standardization, and high validity and reliability, demands the identification and reduction of measurement errors and biases due to poor test design or variation in test items, judges, patients or examination procedures. Generalizability and other research studies have identified where the likely sources of error might arise and have been taken into account in the development of published guidelines on international best practice, which institutions should strive to follow. The purpose of this paper is to describe the development of the integrated final-year assessment of clinical competence at the University of Sheffield. The aim was to introduce a range of strategies to ensure the examination met the best practice guidelines. These included blueprinting the assessment to achieve a high degree of content validity; lengthening the examination by adding a written component to the OSCE component to ensure an adequate level of reliability; providing training and feedback for examiners and simulated patients; paying attention to item development; and providing statistical information to assist the examination committee in standard setting and decision-making. This evidence-based approach should be readily achievable by all medical schools.
Clinical Competence↗
Fluid intake in male and female runners during a 40-km field run in the heat.
To compare physiological responses, hydration status and exercise performance in similarly trained men and women in a hot, humid environment, 12 highly trained runners were studied during a simulated 40-km race. A 7% carbohydrate-electrolyte (CE) beverage was consumed prior to exercise (400 ml) and every 5 km (approximately 250 ml) during the run. The run times of the males and females did not differ significantly (173.5 +/- 8.5 and 183.8 +/- 4.2 min, respectively); nor did the rate of fluid intake relative to body mass (10.3 +/- 0.7 and 10.7 +/- 0.8 ml kg-1 h-1, respectively) or percent body mass loss (4.0 +/- 0.1% and 3.9 +/- 0.1%, respectively). During the run, %VO2 max, heart rate, concentrations of blood lactate, serum total protein and plasma osmolality were also similar for both groups. However, some significant sex differences (P < 0.05) were observed: the females had lower plasma volume losses and higher serum potassium and sodium concentrations than the males during the run. Rectal temperatures were lower in the female runners compared with the males during the last 10 km of the run (0.7 degrees C) and recovery (1.1 degrees C). Findings from this 40-km field run in hot, humid conditions suggest that CE fluid replacement at a relatively similar dosage (approximately 10 ml kg-1 h-1) may have sex-specific physiological effects. These observations warrant further investigation to assess the need for sex-specific fluid replacement guidelines.
Adult↗
ARGformer: learning on ancestral recombination graphs with transformers.
MOTIVATION: Recent advances in inference of the ancestral recombination graph (ARG), which describes how segments of chromosomes trace back through recombination and shared lineages, have made it possible to reconstruct genome-wide genealogies for large cohorts, but it remains difficult to summarize and use this information for population genetic analyses. RESULTS: We present ARGformer, an encoder-only transformer that learns context-dependent embeddings with a self-supervised masked objective finetuned with contrastive learning for downstream retrieval tasks. We train ARGformer on genealogies from coalescent simulations and on genealogies inferred from ancient and present-day Homo sapiens genomes. Using only these learned embeddings, without access to genotype matrices, ARGformer captures patterns of global population structure and supports ancestry inference through clustering and nearest-neighbor retrieval. On genealogies that include archaic hominins, ARGformer can highlight Denisovan-derived segments in Oceanian genomes and reveals Oceanian-like ancestry in South American Indigenous populations. AVAILABILITY AND IMPLEMENTATION: ARGformer is available at https://github.com/AI-sandbox/ARGformer.
Humans↗
Establishing scales of perceived severity for clinical situations during anaesthesia.
BACKGROUND: In many clinical, teaching, and research situations it would be useful to have graded scales of the urgency or other subjective properties for clinical situations that can arise during anaesthesia. Such a scale could serve as a reference point for the appropriate mapping of the urgency in audible alarms or visual warnings, provide a basis for training of graduated difficulty during anaesthesia simulation, provide a benchmark in risk assessment exercises, guide prioritization of decisions in computerized decision support systems for anaesthesia and help in assessing anaesthetist occupational stress. METHODS: A questionnaire-based instrument was developed to assess the perceived severity of a range of anaesthetic clinical situations. Four scales were tested: the severity of the situation for the patient, the urgency of response required by the anaesthetist, attention required by the anaesthetist, and anxiety experienced. Over 300 anaesthetists in three cohorts of 100 were consulted in the selection of the situations to be studied. The final version of the questionnaire, which included 25 situations, was circulated to a further 229 anaesthetists for validation. The pair-wise relationships of the four properties and hence their independence, was examined using Kendall's tau and correlation analysis. RESULTS: The subjective assessments of urgency and attention were closely related, as were severity and anxiety. Comparing the mean rank for the severity scale with the subjective risk scores revealed a statistically significant correlation of tau=0.647 (P<0.01). CONCLUSION: Subjective assessment of severity by anaesthetists was found to be consistent across the clinical situations studied.
Anesthesia↗
Real-time memory on an excitable field.
Recently, we proposed a novel method for computing logic operations based on the time-sequential information in a geometrically arranged excitable field. As an extension of this study, in the present article we describe a strategy for creating real-time memory. Using a numerical simulation, we show that input pulse trains can be stored as a sequence of rotating traveling waves in a circular excitable field, by using its characteristics as a diode due to spatially asymmetric arrangement. Furthermore, through an experiment on an excitable chemical reaction, we demonstrate that this real-time memory actually works in the real world.
Journal Article↗
Formation and dynamics of finite amplitude localized pulses in elastic tubes.
We present theoretical and simulation studies of the formation and dynamics of finite-amplitude localized pulses (solitary waves) of an incompressible fluid in an elastic tube. Starting from a set of hydrodynamic equations, we derive a Hamiltonian which represents the energy integral of our system. The energy integral is analyzed to obtain explicit profiles of finite-amplitude solitary pulses. Also studied are the excitation and dynamics of solitary pulses by using computer simulations. It is found that a train of solitary pulses can be excited by the nonlinear self-steepening at shock fronts. The relevance of our investigation to blood solitary waves in arteries is discussed.
Journal Article↗