Motion sickness and proprioceptive aftereffects following virtual environment exposure.

To study the potential aftereffects of virtual environments (VE), tests of visually guided behavior and felt limb position (pointing with eyes open and closed) along with self-reports of motion sickness-like discomfort were administered before and after 30 min exposure of 34 subjects. When post- discomfort was compared to a pre-baseline, the participants reported more sickness afterward (p < 0.03). The change in felt limb position resulted in subjects pointing higher (p < 0.038) and slightly to the left, although the latter difference was not statistically significant (p = 0.08). When findings from a second study using a different VE system were compared, they essentially replicated the results of the first study with higher sickness afterward (p < 0.001) and post- pointing errors were also up (p < 0.001) and to the left (p < 0.001). While alternative explanations (e.g. learning, fatigue, boredom, habituation, etc.) of these outcomes cannot be ruled out, the consistency of the post- effects on felt limb position changes in the two VE implies that these recalibrations may linger once interaction with the VE has concluded, rendering users potentially physiologically maladapted for the real world when they return. This suggests there may be safety concerns following VE exposures until pre-exposure functioning has been regained. The results of this study emphasize the need for developing and using objective measures of post-VE exposure aftereffects in order to systematically determine under what conditions these effects may occur.

Propranolol for the prevention of postoperative arrhythmias in general thoracic surgery.

BACKGROUND: Prevention of postoperative arrhythmias in patients undergoing general thoracic surgery is desirable to prevent morbidity. METHODS: A randomized, double-blind, placebo controlled trial of propranolol (10 mg every 6 hours) for 5 days was undertaken in patients undergoing major thoracic operations to determine whether arrhythmias requiring treatment could be reduced. Secondary outcomes included overall arrhythmia rate, adverse events, and length of stay. Arrhythmias were assessed by 72-hour Holter monitoring. Patients with a history of heart failure, asthma, advanced heart block, preexisting arrhythmias, sensitivity to propranolol, or use of antiarrhythmic drugs were excluded. RESULTS: Using the intention-to-treat principle there was a 70% relative risk reduction from 20% to 6% in the rate of treated arrhythmias with propranolol (p = 0.071, 95% confidence interval 0.6% to 27.2%). Overall arrhythmias were common but usually benign. Adverse effects were common, although generally mild with hypotension and bradycardia being reported more often in the propranolol group. Length of stay was not different. CONCLUSIONS: There was a trend to a reduction in the risk of perioperative arrhythmias with propranolol. Moreover, propranolol was well tolerated showing a slight increase in minor adverse events.

Effects of alcohol on perceptual speed.

In moderate to heavy doses, alcohol adversely affects performance on many tasks, and perceptual speed is a component in most performance tasks. Nevertheless, studies of alcohol's effects on perceptual speed have been largely limited to critical flicker frequency and backward masking. The present study extends these limits. 16 men and 12 women were administered four temporal-factors tests before and after the ingestion of alcohol. The four tests were Simultaneity, Apparent Movement, Bistable Stroboscopic Motion, and Backward Masking. At the first postalcohol testing (mean BAC = 0.111), all four tests showed pre-posttest changes indicating slowed perceptual speed. Perceptual speed was still slowed when BAC decreased to .096. When mean BAC decreased to .076, however, only Simultaneity and Backward Masking were still significantly slowed. At moderate BACs and possibly at lower ones, the effects of alcohol on task performance appear to be mediated in part by slowed perceptual speed.

Mediastinal parathyroid cysts.

BACKGROUND: Mediastinal parathyroid cysts are a relatively rare clinical entity. The clinical presentation can be quite varied, although most are found incidentally during investigations for esophageal or respiratory symptoms. METHODS: We present a review of the literature and describe two instructive cases showing specific clinical findings. The clinical presentation, radiologic and pathologic findings, and treatment of mediastinal parathyroid cysts are discussed. RESULTS: In the first patient, the presenting symptom was increasing hoarseness resulting from paresis of the right recurrent laryngeal nerve. This case illustrates the rare association of a benign mediastinal parathyroid cyst with unilateral vocal cord palsy. The second patient presented with the more classic findings of progressive dyspnea and stridor related to tracheal compression. CONCLUSIONS: Although mediastinal parathyroid cysts are rare and can have varied presentations, thorough investigation can reveal the underlying cyst. Surgical excision is the treatment of choice and can be expected to produce excellent results.

Disorientation and postural ataxia following flight simulation.

BACKGROUND: Motion sickness-like symptoms can afflict pilots training in military simulators. This simulator sickness involves symptoms of gastrointestinal distress, eyestrain and disorientation. A simulator sickness Questionnaire (SSQ) with subscales available for each of these dimensions has been developed to assess the problem. HYPOTHESIS: This study examined the hypothesis that there is a strong correlation between the SSQ subscale which summarized self report of disorientation symptoms and an objective measure of post-simulation postural instability. METHODS: Data from two Navy simulators were analyzed: Device 2F114, a Weapon System Trainer for the A-6E Intruder, and Device 2F143, an Operational Flight Trainer for the EA-6B. Tests of standing and walking unsteadiness were administered along with the Simulator Sickness Questionnaire (SSQ). RESULTS: Significant correlations were found between scores on postural stability tests and the SSQ disorientation subscale scores, but correlations between scores on postural stability tests and the SSQ nausea and oculomotor subscale scores were much weaker and not statistically significant. CONCLUSIONS: These results provide some evidence for the validity of the disorientation subscale of the SSQ and suggest that the postural instability observed after simulator exposure may, in fact, result from disorientation.

Psychophysical scaling of circular vection (CV) produced by optokinetic (OKN) motion: individual differences and effects of practice.

Vection (V) refers to the compelling visual illusion of self-motion experienced by stationary individuals when viewing moving visual surrounds. The phenomenon is of theoretical interest because of its relevance for understanding the neural basis of ordinary self-motion perception, and of practical importance because it is the experience that makes simulation, virtual reality displays, and entertainment devices more vicarious. This experiment was performed to address whether an optokinetically induced vection illusion exhibits monotonic and stable psychometric properties and whether individuals differ reliably in these (V) perceptions. Subjects were exposed to varying velocities of the circular vection (CV) display in an optokinetic (OKN) drum 2 meters in diameter in 5 one-hour daily sessions extending over a 1 week period. For grouped data, psychophysical scalings of velocity estimates showed that exponents in a Stevens' type power function were essentially linear (slope = 0.95) and largely stable over sessions. Latencies were slightly longer for the slowest and fastest induction stimuli, and the trend over sessions for average latency was longer as a function of practice implying time course adaptation effects. Test-retest reliabilities for individual slope and intercept measures were moderately strong (r = 0.45) and showed no evidence of superdiagonal form. This implies stability of the individual circularvection (CV) sensitivities. Because the individual CV scores were stable, reliabilities were improved by averaging 4 sessions in order to provide a stronger retest reliability (r = 0.80). Individual latency responses were highly reliable (r = 0.80). Mean CV latency and motion sickness symptoms were greater in males than in females. These individual differences in CV could be predictive of other outcomes, such as susceptibility to disorientation or motion sickness, and for CNS localization of visual-vestibular interactions in the experience of self-motion.

Isoperformance curves in applied psychology.

Isoperformance is a technique for reading information out of a data-analytic model, comparable to expected mean square or omega squared analyses. It results in a trade-off function (an isoperformance curve) among the determinants of performance. The technique was developed primarily to generate trade-off functions between personnel aptitude and time in training or on the job. However, the technique is general and can be applied in any trade-off situation. In part, the purpose of this paper is to recall the antecedents of isoperformance in psychophysics and to recount the origins and development of the isoperformance readout. Its main purpose, however, is to present several examples of isoperformance curves in applied psychology and to make the case for their usefulness.

Postural instability induced by virtual reality exposure: development of a certification protocol.

Exposure to virtual environments often causes users to experience symptoms of motion sickness. An accessory manifestation of motion sickness symptoms is postural disequilibrium. If the postural disequilibrium that occurs persists beyond the time an individual is within the confines of the laboratory or system site, user safety could be compromised and products liability issues could be forthcoming. In this study, a portable, automated postural assessment system is developed that can be employed before and after exposure to a virtual reality (VR) system in order to certify that a user's balance on exiting the system is at least demonstrably as good as it was on entering. It is argued that if the "coming out" balance performance is sufficiently poorer than the "going in" balance, then the user should be retained until the pretest balance performance is regained. The results from a set of normative and validation experiments on postural equilibrium identified several reliable measures of stance that could serve as a basis for certification. Furthermore, a new automated video-based measure using only head movement showed that performance over sessions is stable and reliable. The head movement changes that occur with stimuli, such as alcohol and simulator exposure, are well behaved, predictable, and significant even with small samples. The implication is that the proposed objective measure of postural stability, in conjunction with procedures for obtaining self-reports of symptoms, can afford some measure of certification that exposure to a given VR system is without harm.

Temporal factors in visual perception: a differential approach.

The tradition in sensory and perceptual psychology is not to pay much attention to individual differences but to focus almost exclusively on normative or generic processes. Nevertheless, consistent individual differences may exist in sensory and perceptual processes, just as they do in all other areas of human behavior where their existence has been investigated. A preliminary study was made of flicker fusion frequency, apparent movement, and three other perceptual tasks as differential measures. With one exception, Letter Search, all of the tests were psychophysical rather than cognitive. All had to do with time; that is, perceptual speed mattered in all of them. The analysis focused on reliability, in the sense of consistency from trial to trial. Four of the five tests showed good reliabilities in this sense, while the fifth was borderline. In one test, Bistable Stroboscopic Motion, the dependent measure, interstimulus interval, showed a consistent though shallow tendency to lengthen with practice. In the remaining four tests practice effects were largely confined to the first two administrations.

The use of a whey protein concentrate in the treatment of patients with metastatic carcinoma: a phase I-II clinical study.

Glutathione (GSH) concentration is high in most tumour cells and this may be an important factor in resistance to chemotherapy. Previous in-vitro and animal experiments have shown a differential response of tumour versus normal cells to various cysteine delivery systems. More specifically, an in-vitro assay showed that at concentrations that induce GSH synthesis in normal human cells, a specially prepared whey protein concentrate, Immunocal, caused GSH depletion and inhibition of proliferation in human breast cancer cells. On the basis of this information five patients with metastatic carcinoma of the breast, one of the pancreas and one of the liver were fed 30 grams of this whey protein concentrate daily for six months. In six patients the blood lymphocyte GSH levels were substantially above normal at the outset, reflecting high tumour GSH levels. Two patients (#1, #3) exhibited signs of tumour regression, normalization of haemoglobin and peripheral lymphocyte counts and a sustained drop of lymphocyte GSH levels towards normal. Two patients (#2, #7) showed stabilisation of the tumour, increased haemoglobin levels. In three patients (#4, #5, #6,) the disease progressed with a trend toward higher lymphocyte GSH levels. These results indicate that whey protein concentrate might deplete tumour cells of GSH and render them more vulnerable to chemotherapy.

A method for understanding admission decision making in a psychiatric emergency room.

OBJECTIVE: To increase understanding of decisions about inpatient admission, a four-step algorithm was used to examine 2,073 consecutive visits to a public hospital psychiatric emergency room, 684 of which resulted in admission. METHODS: Admission decision outcomes and patient data were cross-tabulated to identify conditions, or rules, under which outcome was almost certain. Discriminant function models were then made of individual clinicians' decision-making process and of individual diagnostic groups. To understand cases not covered in previous steps, a third discriminant function model was constructed. RESULTS: The four-step method successfully predicted outcomes in 85 percent of cases at a minimum of an 80 percent confidence level. The variables of psychosis and violence combined into the most powerful predictor of admission. Twelve rules that applied to 41.4 percent of all cases were found. Eleven models of individual clinicians' decision policies applied to slightly more half of all cases and successfully classified about 95 percent of them. Eleven models of diagnostic groups applied to 93.2 percent of all cases and correctly predicted about 75 percent. The final discriminant model for the 171 cases not covered by the by the first three steps correctly classified about 90 percent of residual cass. CONCLUSIONS: Psychiatric admission decisions are influenced by multiple variables that should be studied by examining general admission criteria and differences between clinicians.

Indexing cognitive tests to alcohol dosage and comparison to standardized field sobriety tests.

Cognitive tests from a computerized battery of mental tests and standardized roadside field sobriety tests (FST) were administered in three experiments involving graded dosages of alcohol but different administration schedules. In the first experiment, subjects were raised to one of four levels of alcohol dosage in four sessions 1 week apart. In the second experiment, the descending branch of the blood alcohol concentration (BAC) curve was monitored from 150 mg/dl BAC in a single session. In the third experiment, the ascending and descending limbs of the alcohol dosage curve were followed over a single session. Dose response relationships were observed for all tests, and the changes were statistically significant (p < .001) in all three studies for all tests when evaluated singly, except for grammatical reasoning. When cognitive and FST tests were combined into a single multiple regression analysis, Gaze Nystagmus consistently accounted for the most variance in BAC, followed by code substitution. While multiple regression analyses reveal that tests from the two batteries can be combined to improve overall prediction of alcohol concentration, it is also true that the two batteries share considerable variance (i.e., > 30%). This suggests that, while the two batteries may not be substitutable, they are measuring different aspects of the same thing.

Quick report for psychiatric emergency rooms.

Translating and pre-digesting the volumes of data from a psychiatric emergency room database into a simple, easy-to-review "quick report" offers a different approach to a rapid review of patient information. Clinicians from psychiatric emergency rooms in New York City were asked to describe the minimal amount of information they would wish to review from previous clinical visits. The smallest report was then constructed to offer the most information.

Relating alcohol-induced performance deficits to mental capacity: a suggested methodology.

Performance tests are generally more reliable and more easily administered than on-the-job measures of performance, and in this way are preferable for studying the adverse consequences of environmental stressors. However, a linkage or context would be useful in interpretation of these laboratory measures. This paper reports findings with two indexing methods using multiple regression. In the first study, we illustrate "dose equivalency" where deficits on microcomputer performance tests were related to graded dosages of alcohol, and prediction equations of blood alcohol level were established. In the second experiment, "surrogate criteria" are demonstrated where cognitive mental tests of military aptitude, known to be predictive of operational performances, were administered to a sample who were tested repeatedly on the same microcomputer performance test. Multiple regression analyses of the computerized tests with the amplitude tests were significant (p < 0.01) and ranged from R = 0.50 to 0.94. Finally, the loss in performance owing to alcohol was indexed to loss on the microcomputer tests through the relationship of the tests to the Armed Services Vocational Aptitude Battery (ASVAB). Since the latter is strongly predictive of all forms of military operational performance, we suggest that alcohol-related losses in microcomputer performance test scores can serve as a useful intermediary, permitting meaningful linkage to these real-world performances.

Postural and performance changes following exposures to flight simulators.

Flight simulators are cost-effective, safe, and flexible training tools for aviators. However, their advantages may be offset by the occurrence of motion sickness-like symptoms which have been reported during and following simulator training. Although symptoms have been well documented in simulators, their time course, causes, and implications for training are not yet fully understood. Tests of standing and walking steadiness were administered along with cognitive and motor performance tests to Navy and Marine Corps aviators before and after their regular simulator training, resulting in records of 726 pilot exposure observations. When exposed pilots were compared to a control group who did not fly in a simulator, statistically significant decrements in postural equilibrium test scores were found for all of the moving base simulators, but for only one of the three fixed-base simulators. The size of these losses was approximately 15% of baseline. Cognitive and motor changes, while statistically significant, were complicated by learning effects in all groups for all tests. When compared to the control group, improvement in cognitive scores was always less in the simulator groups, but greater improvement occurred in the simulator groups for motor speed scores, although this latter difference was small (< 1% of baseline). Further study of performance changes is recommended. In those simulators where significant effects occurred, the ataxia and the time-course of the disequilibrium should be followed.

Effects of graded dosages of alcohol on nine computerized repeated-measures tests.

We report a controlled laboratory validation experiment to provide an empirical sequel to the general background of the development of the Automated Performance Test System (APTS) that was presented in Turnage et al. (1992). The purpose of this study was to index performance deficit against various Blood Alcohol Concentrations (BACs) of small (0.05% BAC), medium (0.10% BAC), and large (0.15% BAC) dosages as well as a placebo (0.00 BAC) condition. Blood alcohol concentrations, measured in four different ways, were highly reliable and the method with the highest intercorrelation was whole blood. When taken singly, eight of the nine tests produced significant (p < 0.001) relationships with the disparate blood alcohol levels, which were essentially monotonic. A multiple regression analysis suggested that most of the tests were behaving similarly and that two or three tests accounted for 52 to 54% of the variance attributable to alcohol that was explained by the longer battery. While all tests appear valid, some of them appeared more sensitive than others (viz., code substitution, manikin, and choice reaction time). From the standpoint of these tests, greater changes occurred in cognitive function between the placebo and 0.05 level than between the 0.05 and 0.10 levels. However, the greatest reduction in performance occurred between 0.10 and 0.15, and the relatively abrupt nature of this change implies that sharp decrements in cognitive performance occur at that point. There were individual differences in resistance to alcohol, and there is strong inference that these differences would be reliable if they were tested again. We believe that further development and study of such techniques is warranted for use in fitness-for-duty testing and development of a dose equivalency index.

Changes in the dark focus of accommodation associated with simulator sickness.

The relationship between the dark focus of accommodation and simulator sickness, a form of motion sickness, was examined in three experiments. In Experiment 1, dark focus was measured in 18 college students in a laboratory setting before and after they viewed a projected motion scene depicting low altitude helicopter flight. In Experiments 2 and 3, dark focus was measured in pilots (N = 16 and 23, respectively) before and after they "flew" in moving-base helicopter flight simulators with optical infinity CRT visual systems. The results showed that individuals who experienced simulator sickness had either an inward (myopic) change in dark focus (Experiments 1 and 3) or attenuated outward shifts in dark focus (Experiment 2) relative to participants who did not get sick. These results are consonant with the hypothesis that parasympathetic activity, which may be associated with simulator sickness, should result in changes in dark focus that are in a myopic direction. Night vision goggles, virtual environments, extended periods in microgravity, and heads-up displays all produce related visual symptomatology. Changes in dark focus may occur in these conditions, as well, and should be measured.

Development of microcomputer-based mental acuity tests.

Recent disasters have focused attention on performance problems due to the use of alcohol and controlled substances in the workplace. Environmental stressors such as thermal extremes, mixed gases, noise, motion, and vibration also have adverse effects on human performance and operator efficiency. However, the lack of a standardized, sensitive, human performance assessment battery has probably delayed the systematic study of the deleterious effects of various toxic chemicals and drugs at home and in the workplace. The collective goal of the research reported here is the development of a menu of tests embedded in a coherent package of hardware and software that may be useful in repeated-measures studies of a broad range of agents that can degrade human performance. A menu of 40 tests from the Automated Performance Test System (APTS) is described, and the series of interlocking studies supporting its development is reviewed. The APTS tests, which run on several versions of laptop portables and desktop personal computers, have been shown to be stable, reliable, and factorially rich, and to have predictive validities with holistic measures of intelligence and simulator performances. In addition, sensitivity studies have been conducted in which performance changes due to stressors, agents, and treatments were demonstrated. We believe that tests like those described here have prospective use as an adjunct to urine testing for the screening for performance loss of individuals who are granted access to workplaces and stations that impact public safety.