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After a slew of retrenchments, split-ups and sliding profits last month, healthcare companies are learning that they probably need to change their game plans and get back to basics. Experts say the same cycle has occurred in other industries and is expected in healthcare.
PURPOSE: Dissociated vertical deviation (DVD) has eluded explanation for more than a century. The purpose of this study has been to elucidate the etiology and mechanism of DVD. METHODS: Eye movement recordings of six young adults with DVD were made with dual-coil scleral search coils under various conditions of fixation, illumination, and head tilt. Horizontal, vertical, and torsional eye movements were recorded for both eyes simultaneously. Analyses of the simultaneous vertical and torsional movements occurring during the DVD response were used to separate and identify the component vergence and version eye movements involved. RESULTS: Typically, both horizontal and cyclovertical latent nystagmus developed upon occlusion of either eye. A cycloversion then occurred, with the fixing eye intorting and tending to depress, the covered eye extorting and elevating. Simultaneously, upward versions occurred for the maintenance of fixation, consisting variously of saccades and smooth eye movements, leading to further elevation of the eye behind the cover. The cyclovertical component of the latent nystagmus became partially damped as the DVD developed. CONCLUSIONS: In patients with an early-onset defect of binocular function, the occlusion of one eye, or even concentration on fixing with one eye, produces unbalanced input to the vestibular system. This results in latent nystagmus, sometimes seen only with magnification. The cyclovertical component of the latent nystagmus, when present, is similar to normal vestibular nystagmus induced by dynamic head tilting about an oblique axis. Such vestibular nystagmus characteristically produces a hyperdeviation of the eyes. In the case of cyclovertical latent nystagmus, the analogous hyperdeviation will persist unless corrected by a vertical vergence. A normal, oblique-muscle-mediated, cycloversion/vertical vergence is called into play. This occurs in the proper direction to correct the hyperdeviation, but it occurs in an exaggerated form in the absence of binocular vision, probably as a learned response. The cycloversion/vertical vergence helps damp the cyclovertical nystagmus (a cyclovertical "nystagmus block-age" phenomenon), aiding vision in the fixing eye. But this mechanism also produces unavoidable and undesirable elevation and extortion of the fellow eye, which we call DVD.
PURPOSE: The etiology and mechanism of dissociated vertical deviation (DVD) are explored. METHODS: In 6 young adults with DVD, the simultaneous horizontal, vertical, and torsional eye movements for both eyes were recorded by using dual-coil scleral search coils. Analysis of the simultaneous vertical and torsional movements that occurred during the DVD response identified the primary muscles acting in the vergences and versions involved. RESULTS: Typically, both horizontal and cyclovertical latent nystagmus developed upon occlusion of either eye. A cycloversion/vertical vergence then occurred, with the fixing eye intorting and tending to depress and the covered eye extorting and elevating. Simultaneously, upward versions occurred for the maintenance of fixation, consisting of various saccades and smooth eye movements, and this led to further elevation of the eye behind the cover. The cyclovertical component of the latent nystagmus became partially damped as the DVD developed. CONCLUSIONS: In patients with an early onset defect of binocular function, the occlusion of one eye, or even concentration on fixing with one eye, produces unbalanced input to the vestibular system. This results in latent nystagmus with a cyclovertical component, sometimes only seen with magnification. A normal, oblique-muscle-produced, cycloversion/vertical vergence then comes into play, occurring in an exaggerated form in the absence of binocular vision, probably as a learned response. This cycloversion/vertical vergence helps damp the cyclovertical nystagmus (a cyclovertical "nystagmus blockage" phenomenon), aiding vision in the fixing eye. But this mechanism also produces unavoidable and undesirable elevation and extorsion of the fellow eye, which we call DVD.
The UMVF aims at helping medical students during their normal curriculum via the facilities provided by Internet based techniques. This paper describes a comparative assessment of two interfaces delivering a multimedia course: a conventional web server (WS) and an integrated e-learning platform in the form of a Virtual Campus (VC). Eleven students were arbitrarily divided into two groups. We used a qualitative method for comparing their acceptance of the on line course provided by the two different interfaces. The two groups were globally satisfied. However, a decrease in satisfaction was noted at the end of the experimentation in the VC group. This may be explained by a more complex Graphical User Interface (GUI) of the VC and some constraints which do not exist with the WS. The current e-learning platforms are probably not optimised for working conditions where presential and virtual activities are mixed. We think that a new type of "light" platforms should be developed for these specific working conditions. Students of the two groups also had limitations about the multimedia environment. They may change their opinion if they get more accustomed with the multimedia environment and if their teachers make a more adequate use of the multimedia techniques.
Early attempts to understand the causes of physician stress focused almost exclusively upon the role of external stressors and demands. Recent psychosocial and behavioral research, however, suggests that individual attitudes, beliefs, personality factors, and learned coping strategies probably play a more important role. In addition, such cognitive and behavioral tendencies are within the control of each individual, and clinical experience has shown that these factors can indeed be modified. Freudenberger noted that most health professionals who are experiencing high levels of stress fail to identify the role that they themselves play in generating such symptoms. Instead, they tend to blame others as the cause of their problems and tend to react cynically toward suggestions that they could benefit from help. A large-scale study of family physicians in North Carolina, conducted by May, Revicki, and Jones in 1983, confirmed the fact that most physicians who reported a high level of professional stress also tended to score high on measures of external locus of control--i.e. the perception that external or environmental factors are mainly responsible for one's problems or successes. My own experience in treating physicians and other people with stress tends to confirm these findings. More importantly, I have found that once individuals are helped to identify the role that their own cognitive and behavioral tendencies play in the origin of their stress, they can usually bring about impressive reductions in stress and tension without significant changes in environmental factors or demands. While many people advocate stress-releasing and other relaxation skills for physicians, I have found that such approaches are often counterproductive.(ABSTRACT TRUNCATED AT 250 WORDS)
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BACKGROUND: In order to elucidate mental functions that subserve human consciousness, brain activation was investigated in 12 normal, right-handed volunteers who performed tasks of selective attention, working memory, and sensorimotor coordination during the collection of multislice echoplanar functional magnetic resonance images. HYPOTHESIS: These functions are located in (and controlled by) distinct anatomical regions that can be identified by functional magnetic resonance imaging techniques. METHODS: In each subject, 100 10-slice data sets were acquired using a 1.5-T scanner and the blood oxygenation level dependent contrast technique. Time-series regression modeling estimated power in the magnetic resonance signal during the on/off phases of task performance. Comparison between subjects was made possible by the transformation of each data set into standard Talairach space. RESULTS: Activation maps were based on the median value of the fundamental power quotient at each voxel. Results showed the activation of prefrontal and parasagittal cortices in both the selective attention and working memory tasks, but they also revealed activation in both insular cortices and the posterior cingulate gyri. CONCLUSIONS: The results provide evidence for structures in the anterior right hemisphere and left medial frontal lobe for attentional tasks, although there appears to be an engagement of a widespread network of anterior brain structures, possibly with the inhibition of some posterior regions, during task performance. The sensorimotor coordination task showed activation regions similar to those seen in selective attention. Once learned, this task probably demands attention rather than overt conscious motor control. Clearly, the functions of attention, working memory, and sensorimotor coordination are not located in single, discrete brain areas. However, interactions and interplay between related areas were demonstrated, giving supporting evidence that complex mental operations rely on the coordinated activity of widely distributed brain regions that contribute to neural networks.
Feedback to physicians about how they use information in making judgments can improve the quality of their judgments, but questions remain about which types of feedback are most effective. The authors conducted a controlled study of feedback in 60 medical students learning to predict the risk of cardiovascular death based on the presence or absence of five risk factors. After a pretest of 40 cases abstracted from patient records, the students worked through 173 computer-simulated cases and a posttest of 40 patient cases. The students received no feedback, probability feedback (correct probability of cardiac death for each case), cognitive feedback (the correct cue weights compared with their own weights derived from the previous set of cases), or both types of feedback. Students who received probability feedback markedly improved both base rate calibration and discrimination. Those who received only cognitive feedback showed no improvement over control on any of the measures of learning. All subjects were highly consistent in their weightings. The superiority of probability feedback differed from previous findings that cognitive feedback was essential for mastery of multiple-cue-probability learning tasks. The information on cue-outcome relationships given by cognitive feedback may be more useful when these relationships are complex and the combining rule is not known, while the precise outcome information provided by probabilistic feedback is more useful when the combining rule is known and the cue-outcome relationships are straightforward. Thus, the optimal method of learning depends on the nature of the task.
The challenging task of medical diagnosis based on machine learning techniques requires an inherent bias, i.e., the diagnosis should favor the "ill" class over the "healthy" class, since misdiagnosing a patient as a healthy person may delay the therapy and aggravate the illness. Therefore, the objective in this task is not to improve the overall accuracy of the classification, but to focus on improving the sensitivity (the accuracy of the "ill" class) while maintaining an acceptable specificity (the accuracy of the "healthy" class). Some current methods adopt roundabout ways to impose a certain bias toward the important class, i.e., they try to utilize some intermediate factors to influence the classification. However, it remains uncertain whether these methods can improve the classification performance systematically. In this paper, by engaging a novel learning tool, the biased minimax probability machine (BMPM), we deal with the issue in a more elegant way and directly achieve the objective of appropriate medical diagnosis. More specifically, the BMPM directly controls the worst case accuracies to incorporate a bias toward the "ill" class. Moreover, in a distribution-free way, the BMPM derives the decision rule in such a way as to maximize the worst case sensitivity while maintaining an acceptable worst case specificity. By directly controlling the accuracies, the BMPM provides a more rigorous way to handle medical diagnosis; by deriving a distribution-free decision rule, the BMPM distinguishes itself from a large family of classifiers, namely, the generative classifiers, where an assumption on the data distribution is necessary. We evaluate the performance of the model and compare it with three traditional classifiers: the k-nearest neighbor, the naive Bayesian, and the C4.5. The test results on two medical datasets, the breast-cancer dataset and the heart disease dataset, show that the BMPM outperforms the other three models.
A cognitive-distance model for choice, obtained by specializing a general class of models for categorization, was tested in a situation simulating the task of controlling speed of a vehicle in tasks defined by different relations between speed and probability of delay. Subjects exhibited significant learning whenever delay schedules permitted greater-than-chance performance, but on the average they did not approach optimal performance in the sense of choosing speeds so as to maximize distance attained in allowed time. Evidence was obtained that subjects encoded information about probabilities of delay and distributions of distance attained at different speeds quite accurately in memory and that suboptimal performance was due primarily to imperfect discrimination among representations of choice alternatives on a cognitive scale of expected distance.
Electromyographic biofeedback is commonly used successfully to treat tension-type headache, while thermal biofeedback is considered the best behavioral therapy for migraine. Ten female patients with episodic common migraine (age 20-35 years, age of disease onset 16.2 +/- 5.1 years, illness duration 13.6 +/- 10.7 years) were treated by 16 twice-weekly electromyographic biofeedback and relaxation training sessions with breathing exercises. Follow-up sessions were held 1,3,6 and 12 months after the end of treatment. A significant decrease in migraine episodes was noted after therapy. More importantly, pain episodes continued to decline up to the last follow-up 12 months later. Electromyographic activity was within the normal range throughout treatment and follow-up, and there was no relationship between electromyographic activity and pain index. It is concluded that the results, particularly after a year's follow-up, are encouraging for the use of this technique to treat migraine. However, the behavioral changes and increased well-being did not correlate with muscular tension. Control of breathing, peripheral temperature and muscle activity are probably important common factors mediating learned ability to influence sympathetic activity; it is probably the latter which leads to reduced pain in migraine patients.
In this paper, we analyze stochastic gradient learning rules for posterior probability estimation using networks with a single layer of weights and a general nonlinear activation function. We provide necessary and sufficient conditions on the learning rules and the activation function to obtain probability estimates. Also, we extend the concept of well-formed cost function, proposed by Wittner and Denker, to multiclass problems, and we provide theoretical results showing the advantages of this kind of objective functions.
Ten acquisition curves were obtained from each of 4 pigeons in a two-choice discrete-trial procedure. In each of these 10 conditions, the two response keys initially had equal probabilities of reinforcement, and subjects' choice responses were about equally divided between the two keys. Then the reinforcement probabilities were changed so that one key had a higher probability of reinforcement (the left key in half of the conditions and the right key in the other half), and in nearly every case the subjects developed a preference for this key. The rate of acquisition of preference for this key was faster when the ratio of the two reinforcement probabilities was higher. For instance, acquisition of preference was faster in conditions with reinforcement probabilities of .12 and .02 than in conditions with reinforcement probabilities of .40 and .30, even though the pairs of probabilities differed by .10 in both cases. These results were used to evaluate the predictions of some theories of transitional behavior in choice situations. A trial-by-trial analysis of individual responses and reinforcers suggested that reinforcement had both short-term and long-term effects on choice. The short-term effect was an increased probability of returning to the same key on the one or two trials following a reinforcer. The long-term effect was a gradual increase in the proportion of responses on the key with the higher probability of reinforcement, an increase that usually continued for several hundred trials.
MOTIVATION: Alternative splicing (AS) is a frequent step in metozoan gene expression whereby the exons of genes are spliced in different combinations to generate multiple isoforms of mature mRNA. AS functions to enrich an organism's proteomic complexity and regulates gene expression. Despite its importance, the mechanisms underlying AS and its regulation are not well understood, especially in the context of global gene expression patterns. We present here an algorithm referred to as the Generative model for the Alternative Splicing Array Platform (GenASAP) that can predict the levels of AS for thousands of exon skipping events using data generated from custom microarrays. GenASAP uses Bayesian learning in an unsupervised probability model to accurately predict AS levels from the microarray data. GenASAP is capable of learning the hybridization profiles of microarray data, while modeling noise processes and missing or aberrant data. GenASAP has been successfully applied to the global discovery and analysis of AS in mammalian cells and tissues. RESULTS: GenASAP was applied to data obtained from a custom microarray designed for the monitoring of 3126 AS events in mouse cells and tissues. The microarray design included probes specific for exon body and junction sequences formed by the splicing of exons. Our results show that GenASAP provides accurate predictions for over one-third of the total events, as verified by independent RT-PCR assays. SUPPLEMENTARY INFORMATION: http://www.psi.toronto.edu/GenASAP.
A simple hypothesis can explain the results obtained to date if we disregard those results when we wait 30 minutes after original learning to inject. The hypothesis is that, as a result of learning, the postsynaptic endings at a specific set of synapses become more sensitive to transmitter. This sensitivity increases with time after initial learning and then declines. The rate at which such sensitivity increases depends on the amount of initial learning. If the curve of transmission plotted against time is displaced upward with anticholinesterases then the very low portions will show facilitation, and the high portions will cause block (Fig. 8). The middle portions will appear unaffected (unless special experimental tests are made). If the curve of transmission is displaced down with anticholinergics, then the middle portion will appear unaffected and only the very early or late components will show block. The results are evidence that synaptic conductance is altered as a result of learning. So far it seems (i) that cholinergic synapses are modified as a result of learning and that it probably is the postsynaptic membrane that becomes increasingly more sensitive to acetylcholine with time after learning, up to a certain point. (ii) After this point, sensitivity declines, leading to the phenomenon of forgetting. (iii) There is also good evidence that there is an initial phase of declining sensitivity to cholinesterase or increasing sensitivity to anticholinergics. This could reflect the existence of a parallel set of synapses with fast decay that serve as a shortterm store. (iv) Increasing the amount of learning leads to an increase in conductance in each of a set of synapses without an increase in their number. (v) Both original learning and extinction are subserved by cholinergic synapses.
A set of four manipulanda were presented to four Cebus monkeys, individually, and later in pairs. Step 1 provided an estimate of each S's probability of operating each item, while Step 2 determined whether pairing the items would disturb the ordinal relations among individual response probabilities. Both procedures provided information necessary for testing the assumption that a reinforcer is simply a contingent response whose independent probability of occurrence is greater than that of the associated instrumental response. Step 3 tested this assumption by again presenting pairs of items, but with one locked and its operation made contingent upon operation of the free item of the pair. The four Ss differed markedly in the extent to which the items produced different independent response probabilities, and correspondingly, in the extent to which the contingent pairs subsequently produced reinforcement. Confirmation of the present assumptions came primarily from one S, which differed substantially on the individual items, and showed five cases of reinforcement, all in the predicted direction. Further, reinforcement was shown by an increase in both contingency and extinction sessions. Finally, the response of intermediate probability reinforced the response of least, but not the one of greatest, probability, indicating that a reinforcer cannot be identified absolutely, but only relative to the base response.
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