Do Visual Background Manipulations Reduce Simulator Sickness? Presence reflects selected rest frame decisions. What stimuli influence selected rest frame decisions? This leads to techniques for modulating the sense of presence in virtual environments (see Prothero etal., 1. B). What are the consequences when selected rest frames are inconsistent with somecues (most usually, visual or inertial cues)? This produces at least two interesting subcases. Area III A. Visual cues determine rest frame selection. Sort: Preset Date Alphabetical Plays Likes Comments Duration. Search within these results: or cancel. As discussed briefly below, this appears to lead to a usefulway of linking together presence and six classes of visual illusions. No functional selectedrest frame is formed at all. As a slight refinement to sensory rearrangement theory, we suggest that thiscondition is the underlying cause of motion sickness. We wouldexpect that manipulations to the perceived visual background would be one means to alter the selectedrest frame. The visual background generally defines the largest set of coherent cues in the environment. Therefore, calculations performed by the nervous system can be simplified by assigning this set of cuesto be the rest frame, and thus as forming the comparator for spatial judgments. For 5 of these 6 cases, it is well- known that visual background manipulations canproduce the indicated illusion. For orientation, tilting the visual background can produce perceived tilt inthe opposite direction, both for self and for objects in the environment. For motion, illusory self- motioninduced by visual stimuli is referred to as . Both kinds of illusions can be created by moving the perceived visual background. For position, the perceived distance to an object can be altered by perspective manipulations in thevisual background: for instance, the . The sixth illusion is self and position. Wesuggest that all six of these illusions are sub- components of presence. The link between reportedpresence and the visual background is discussed in (Prothero et al., 1. B). The. Rest Frame Hypothesis suggests that motion sickness does not arise from conflicting motion signals perse, but rather from conflicting rest frames deduced from those motion signals. Title: Mimic (1997) 5.9 /10. Want to share IMDb's. Suggested Readings Old, 1997, Principles of gene manipulations, Blackwell Publication, UK Paterson, from BI 200 at Montgomery College. SIGNIFICANT MANIPULATIONS OF THE CONTROLS FOR POWER REACTOR OPERATOR LICENSING Addressees. 1997, the NRC determined that a violation of. That is, what is crucial isnot the full set of motion cues in the environment, but rather how those motion cues are interpreted toinfluence one's sense of what is and is not stationary. For instance, if one is seated on a bench watchinga flock of birds approaching, one has conflicting motion signals (the birds indicate a relative motion, theinertial cues do not). However, one is very unlikely to become motion sick, because one's perceptualsystem is unlikely to interpret the flock of birds as defining the stationary rest frame, and, as such,indicating self- motion. Other rest frame cues, from the ground or the sky, are more influential than theflock of birds. Start studying Antecedent Manipulations (ABI). Learn vocabulary, terms, and more with flashcards, games, and other study tools. Waste Management Founder, Five Other Former Top Officers. Schultz, 1997) at the treatment. The biomechanics of spinal manipulation 281. Neck Manipulation: Risk vs. Benefit Posted by Sam Homola on August 27, 2009. While manipulation of any kind has the potential to cause injury, stroke caused by neck. As implied above,visual background manipulations may serve to reduce motion sickness. Benefit « Science- Based Medicine. Posted by Sam Homola on August 2. While manipulation of any kind has the potential to cause injury, stroke caused by neck manipulation is of greatest concern. Types of Earnings Management and Manipulation. Earnings manipulation is usually not the result of an intentional fraud, but the culmination of a series of aggressive. Risk must always be weighed against benefit when upper neck manipulation is considered. Risk of stroke caused by neck manipulation is statistically low, but the risk is serious enough to outweigh benefit in all but a few rare, carefully selected cases. When the RAND (Research and Development) organization published its review of the literature on cervical spine manipulation and mobilization in 1. In the same year, after examining 1. National Chiropractic Mutual Insurance Company (NCMIC) concluded that “It has to be accepted that VBS . A chiropractor- authored review of malpractice data provided by the Canadian Chiropractic Protective Association, for example, concluded that a chiropractor will be made aware of an arterial dissection only once per 5. This stroke- manipulation ratio is widely quoted by chiropractors, despite the fact that court- litigated cases do not reflect the total number of manipulation- related strokes, most of which are unreported or undetected. Backing away from observations that neck manipulation is a cause of stroke, a 2. NCMIC Chiropractic Solutions concluded that “The incidence of stroke in the population as a whole is no different (2 per 1. The best scientific evidence available has shown no causative relationship between appropriately applied spinal manipulation and stroke events. No consideration is given to the possibility that many strokes caused by neck manipulation may go unreported. When patients seek medical care for paralytic symptoms caused by release of a blood clot that was formed days or weeks earlier by neck manipulation, for example, a connection between neck manipulation and stroke may not be made. Such strokes may then be reported by primary care physicians who are unaware of preceding trauma caused by neck manipulation, thus sparing chiropractors of any blame. The most recent chiropractor- headed study of the association between chiropractic visits and vertebrobasilar artery stroke, based on billing records, concluded that strokes associated with chiropractic neck manipulation occur because patients with headache and neck pain caused by vertebrobasilar dissection seek chiropractic care for relief of symptoms: “The increased risks of VBA stroke associated with chiropractic and PCP . It goes without saying, however, that it is the responsibility of the chiropractor to recognize symptoms of stroke before manipulating the patient’s neck, especially if the chiropractor practices independently or portrays himself or herself as a primary care physician. But you cannot depend upon the diagnostic acumen of a chiropractor who believes that he or she can improve health by adjusting the spine. Physicians and therapists who refer patients to chiropractors must be cautious in selecting patients for referral, and they must take responsibility for the diagnosis when making such referrals. Clearly, patients with acute head and neck pain that might be the result of stroke or arterial dissection should not have their necks manipulated. Elderly persons who might be susceptible to stroke because of diseased vertebral arteries should not be subjected to the risk of neck manipulation. The fact that spontaneous vertebral artery dissection can occur in susceptible persons of all ages does not excuse neck manipulation as a cause of traumatic dissection but rather underscores another reason for avoiding such treatment whenever possible. Appropriate neck manipulation. Manipulation of the upper cervical spine should be reserved for carefully selected musculoskeletal problems that do not respond to such simple measures as time, massage, exercise, mobilization, longitudinal traction, or over- the- counter medication. Because of the tortuous route of the vertebral arteries where they thread through the transverse processes of the first cervical vertebra and then make a sharp turn to travel behind the atlas and enter the skull through the foramen magnum, head and neck rotation forced by manual manipulation should not exceed 4. Rotating the head to rotate the cervical spine would force excessive rotation in the occiput- atlas- axis area where the vertebral arteries are most vulnerable and where there are no intervertebral discs and no interlocking joints to limit rotation. The slow stretching of mobilization within a normal range of movement may be less damaging to arteries than the high- velocity low- amplitude manipulation required to rotate the cervical spine beyond its normal range of motion or to move joints into the paraphysiologic space to produce cavitation. It seems likely that in rare cases where there is significant discomfort or loss of mobility caused by binding or fixation of a vertebral joint or by entrapment of a synovial membrane or a cartilaginous fragment, manipulation might be the treatment of choice. There is evidence to indicate that cervical spine manipulation and/or mobilization may provide short- term pain relief and range of motion enhancement for persons with subacute or chronic neck pain. There is no credible evidence, however, to indicate that neck manipulation is any more effective for relieving mechanical neck disorders than a number of other physical treatment modalities,9 and it is clear that adverse reactions are more likely to occur following manipulation than mobilization. When manipulation is performed, a joint is moved farther than normally possible in an active movement. Passive mobilization moves a joint through its normal range of motion.) Inappropriate cervical spine manipulation may force excessive movement and worsen symptoms related to cervical disc herniation or spondylosis, producing such complications as radiculopathy or myelopathy. At least one study has suggested that manual therapy in the form of mobilization is more effective and less costly for treating neck pain that physiotherapy or care by a general practitioner. And there is reason to believe that less risk is associated with mobilization than with manipulation. There is no justification, however, for use of neck mobilization or manipulation as a treatment for general health problems. All things considered, manual rotation of the cervical spine beyond its normal range of movement is rarely justified. The neck should never be manipulated to correct an asymptomatic. There is no evidence that such subluxations exist. When a painful, actual subluxation (partial dislocation) occurs, manipulation might occasionally be helpful but is most often contraindicated. The bottom line is that while there might an occasional need for appropriate, properly controlled neck manipulation in the treatment of an uncomplicated musculoskeletal problem that results in loss of mobility, there is no credible support for the use of such treatment based on the chiropractic vertebral subluxation theory. Consultation with an orthopedist or a neurologist should be part of a consensus that determines the need for neck manipulation, weighing benefit against risk. Persons with certain structural or vascular abnormalities, or who might be taking blood thinners or other medications that would increase risk of bleeding, would be advised not to undergo neck manipulation for any reason. When a sudden onset of neck pain occurs, it is absolutely essential that an attempt be made to. Sudden, severe headache might also be an indication that stroke is occurring or is about to occur. When neck pain or headache is sudden and severe, neck manipulation should not be considered until a neurologist has tested the patient for symptoms of arterial dissection or stroke. Such a careful approach would be problematic among chiropractors who base diagnosis and treatment upon detection and correction of a “vertebral subluxation complex.”1. Chiropractors vs. A physical therapist trained in the use of both manipulation and mobilization for musculoskeletal problems would be less likely to use manipulation inappropriately than a chiropractor who routinely manipulates the spine for “the preservation and restoration of health.”1. According to the Association of Chiropractic Colleges (ACC), “Chiropractic is concerned with the preservation and restoration of health, and focuses particular attention on the subluxation. A subluxation is a complex of functional and/or structural and/or pathological articular changes that compromise neural integrity and may influence organ system function and general health.”1. Chiropractors who are guided by this vague paradigm (more of a belief than a theory) often manipulate the full spine of every patient for “subluxation correction.” Few chiropractors specialize in the care of back pain and other musculoskeletal problems, and only a few have renounced the chiropractic vertebral subluxation theory. An indication that science- based chiropractic is outweighed by subluxation- based chiropractic is evident in the recent demise of the National Association for Chiropractic Medicine (NACM). Only a few hundred chiropractors joined the organization. Failure of the NACM certainly does not speak well for the chiropractic profession, which continues to resist reform that would uniformly limit chiropractors in a properly defined specialty. While physical therapists, physiatrists, osteopaths, and orthopedists sometimes manipulate the neck for a carefully selected musculoskeletal problem, chiropractors who are guided by the ACC’s subluxation paradigm may routinely manipulate the neck. Unfortunately, there is no official or legal definition limiting chiropractors to treatment of musculoskeletal problems, making it difficult to find a properly limited chiropractor. There is little doubt that most chiropractors are skillful manipulators. And many chiropractors do a good job treating back pain.
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