Head roll compensation in a visually coupled HMD: considerations for helicopter operations.

BACKGROUND: The helmet-mounted display (HMD) research program at the Flight Research Laboratory of the National Research Council of Canada examined the effects of HMD camera platform dynamics on pilot workload. Many currently fielded visually coupled HMD systems do not reproduce head movements in the roll axis which can lead to the presentation of visual information that is not consistent with vestibular and proprioceptive information. HYPOTHESIS: Our hypothesis was that this sensory conflict can induce motion sickness and increase pilot workload. METHODS: To examine this premise, three pilots flew a series of standardized maneuvers with or without roll compensation in the camera platform of a visually coupled HMD system. RESULTS: Increases in motion sickness symptoms and pilot workload were noted during complex, high-workload maneuvers when no roll compensation was present in the camera platform. During the most demanding maneuvers, the lack of roll compensation in the camera platform made it difficult for the evaluation pilot to control the helicopter. CONCLUSIONS: Roll compensation in visually coupled HMD systems reduces pilot workload and' motion sickness during critical flight periods where pilot workload may already be considerable.

Control' of reflexive and voluntary saccades in the gap effect.

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism. Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array--a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.

Evidence for selective target processing with a low perceptual load flankers task.

In this article, we demonstrate that selective target processing is possible when the perceptual load of the task is low. We presented a row of three items with two different identities: one identity for the target letter and one for the two flankers (B. A. Eriksen & C. W. Eriksen, 1974). Such stimulus arrays have been defined as low-load displays (Lavie & Tsal, 1994). We investigated whether subjects could ignore the irrelevant flankers, which were never response alternatives, by manipulating the predictive relationship between the flankers and the response (Miller, 1987). In a high-correlation block, the identity of the flankers was highly predictive of the target identity, whereas in a low-correlation block, the predictive value of the flankers was reduced. We varied (1) whether or not the target location was precued, (2) the flanker's category (digit vs. letter), (3) the target-flanker proximity (near = .3 degree vs. far = 5 degrees), and (4) the size of the characters. The results indicate that subjects were influenced by the predictive value of near flankers and that the magnitude of this effect was jointly modulated by the target-flanker categorical overlap and by the size of the characters. In contrast, null flanker effects were obtained for far letter flankers in the precue condition, and for far digit flankers, regardless of attentional cuing. These findings (1) are inconsistent with suggestions (Lavie, 1995) that irrelevant stimuli automatically capture attention, and (2) support the notion that target-flanker distinctiveness plays a role when the perceptual load of the task is low.

Salmon calcitonin nasal spray in the prevention of corticosteroid-induced osteoporosis.

The objectives were to determine the efficacy and safety of nasal salmon calcitonin 200 IU daily in the prevention of corticosteroid-induced osteoporosis. A minimized, double-blind, placebo-controlled trial was carried out in corticosteroid-treated patients with polymyalgia rheumatica. The setting was a tertiary care university-affiliated hospital and a total of 31 patients were enrolled. The primary outcome measure was the percentage change in bone mineral density of the lumbar spine in the two treatment groups from baseline to 1 yr of follow-up. The mean +/- S.D. bone mineral density of the lumbar spine in the calcitonin-treated group decreased by 1.29 +/- 6.76% and in the placebo group by 4.95 +/- 3.50% after 12 months. The observed difference of 3.65 +/- 2.10% between groups is statistically significant (P < 0.05). Nasal salmon calcitonin prevented loss of bone in the lumbar spine as measured by dual-energy X-ray absorptiometry.

Intermittent cyclic therapy with etidronate prevents corticosteroid-induced bone loss: two years of follow-up.

The purpose of this study was to evaluate the efficacy of intermittent cyclic therapy (ICT) with etidronate in preventing the loss of lumbar vertebral bone mineral density (BMD) in patients taking corticosteroids. The study population was a cohort of patients taking corticosteroids for at least two years for polymyalgia rheumatica, asthma, rheumatoid arthritis, systemic lupus erythematosus or other conditions. A tertiary care university teaching hospital-affiliated rheumatology office practice. Inclusion and exclusion criteria yielded eighty-eight patients taking corticosteroids for at least two years who had not taken estrogen or fluoride and had no causes of secondary osteoporosis. Changes relative to baseline in individual vertebral (L2-L4) BMD measurements after one and two years were compared between patients who had taken ICT with etidronate (n = 42) and those who had not (n = 46). We found that BMD in the lumbar spine increased significantly over baseline in patients who had taken ICT with etidronate, by 3.9% after one year and by 5.6% after two years, whereas it decreased by 3.7-3.8% in patients who had not. We conclude that ICT with etidronate prevents corticosteroid-induced osteoporosis and progressively ameliorates BMD over two years. Double blind trials are underway to evaluate whether this increased BMD is associated with reductions in vertebral fracture rates.

Intermittent cyclic therapy with etidronate in the prevention of corticosteroid induced bone loss.

OBJECTIVE: To assess the potential efficacy of intermittent cyclic therapy (ICT) with etidronate in the treatment of patients with corticosteroid induced osteoporosis. METHODS: Cohort study in a tertiary care university affiliated hospital in corticosteroid treated patients, with polymyalgia rheumatica, asthma, systemic lupus erythematosus, rheumatoid arthritis, or temporal arteritis, examining the effects of ICT etidronate. Patients were included if they were taking corticosteroids for a minimum of one year. Comparison patients were those who had been taking corticosteroids for a minimum of one year and who had not been treated with etidronate or other medication which might alter bone metabolism. A total of 68 patients were included from 253 considered. The mean (SD) dose of prednisone in the ICT etidronate treated patients was 9.3 (6.2) mg and in the comparison patients 9.4 (5.9) mg. The duration of prednisone therapy was 7.8 (5.8) years and 3.4 (4.2) years, respectively (p2 < 0.001). An analysis of covariance demonstrated that this difference did not alter our primary outcome measure. The primary outcome measure was the difference in the percentage change from baseline to one year of followup in bone mineral density (BMD) of the lumbar spine between treatment and comparison groups. RESULTS: ICT etidronate resulted in a statistically significant and clinically important increase in BMD. The BMD of the lumbar spine increased by 3.82% (0.65%), [95% confidence interval (CI), 2.51 to 5.14%] in the 35 ICT etidronate treated patients and decreased by 1.78% (0.76%), [95% CI, -3.34 to -0.23%] in the 33 comparison patients after 12 months (p2 < 0.0001). CONCLUSIONS: ICT etidronate prevented loss of vertebral bone density in patients with corticosteroid induced osteoporosis. Controlled, double blind, prospective trials with longer followup are needed to confirm these results and to demonstrate that increases in bone mass translate into decreased fracture rates.

Reaction time measures of feature saliency in schematic faces.

Two separate paradigms utilizing measurements of reaction time were employed to study facial feature saliency in schematic line drawn faces. In the first paradigm the speed of response to the omission of different facial components was measured, and in the second, the speed of response to feature substitution was measured. In both paradigms the facial features were presented in a random temporal sequence in order to minimise preferential scanning strategies. The two separate paradigms reflected the feature hierarchy most commonly found in the literature, ie the outline and eyes are more salient than the nose and mouth in terms of both speed of processing and error rate. In a third study the feature substitution paradigm was used to investigate the effects of feature saliency on the perception of emotional faces. The results suggest a change in the eyes/mouth hierarchy so that the mouth becomes the most salient feature in the surprised, happy, and sad target faces. This reverse in hierarchy, however, was not evident with the angry target face. These results are discussed in terms of changes in the focus of 'attention' and/or changes in 'processing efficiency'.

Gold induced thrombocytopenia: 12 cases and a review of the literature.

Gold induced thrombocytopenia is immune mediated, with the production of platelet associated IgG leading to peripheral platelet destruction. An association with HLA-DR3 has been demonstrated. Corticosteroid therapy is effective in treatment, although other modes of therapy may be as efficacious.

Antirheumatic drugs: clinical pharmacology and therapeutic use.

With the exception of the treatment of gout and bacterial infections of joints, therapy in the rheumatic diseases remains inadequate. Although many patients gain symptomatic improvement on the drugs currently available, their impact on the underlying disease process remains uncertain. Hope for future therapeutic development is highest in rheumatoid arthritis with the second-line agents (e.g. gold, penicillamine), as unravelling their mechanism of action may lead to the design of more effective and less toxic medications. The cytotoxic agents appear to hold some promise in the therapy of vasculitis, but problems with their use have by no means been solved. In the major problem area of osteoarthritis, important gains are being made in the field of joint replacement, and the use of non-steroidal anti-inflammatory drugs in the interim has made symptoms more tolerable. Obviously much remains to be done in research in the area of antirheumatic drugs.