The Perception of an Optical Flow Projected on the Ground Surface

Perception ◽  
1988 ◽  
Vol 17 (5) ◽  
pp. 633-645 ◽  
Author(s):  
Michelangelo Flückiger ◽  
Bernard Baumberger
Keyword(s):  
Visual Information ◽  
Postural Stability ◽  
Ground Surface ◽  
Body Sway ◽  
Centre Of Gravity ◽  
Postural Responses ◽  
Outdoor Setting ◽  
Linear Vection ◽  
Ecological Specificity

In most experiments in which the importance of visual control on postural stability is studied, optical stimuli attached to vertical surfaces are used. Analyses of long-term standing readjustments generally involve back-and-forth movements of a visual scene or its projection on vertical circular screens. In a natural environment, however, visual information is largely available from the ground. The aim of the experiment reported was to assess the effect of a flow pattern simulating an open outdoor setting on motion perception and postural control. Subjects were presented with an optical texture projected onto the ground. Periods of motionless texture alternated with equivalent durations of unidirectional flows. The change of position of the subject's centre of gravity over time was recorded on a force platform. Results show that the direction of body sway corresponded with that of texture motion. Important aftereffects, as shown in linear vection experiments, were also observed. However, the latency of postural responses was much shorter than with prolonged unidirectional flows produced in other locations of the visual environment. The hypothesis of an ecological specificity of the flows perceived on the ground during terrestrial displacements is discussed.

Tullio Phenomenon and Postural Stability: Experimental Study in Normal Subjects and Patients with Vertigo

1991 ◽  
Vol 100 (12) ◽  
pp. 976-983 ◽  
Author(s):  
Hisayoshi Ishizaki ◽  
Heikki Aalto ◽  
Ilmari Pyykkö ◽  
Jukka Starck
Keyword(s):  
Inner Ear ◽  
Postural Stability ◽  
Chronic Otitis Media ◽  
Normal Subjects ◽  
The Body ◽  
Body Sway ◽  
Tullio Phenomenon ◽  
Postural Responses ◽  
Different Types ◽  
Inner Ear Disease

The effect of low-frequency sound (LFS) on postural stability was studied in 55 healthy volunteers and in 152 patients with vertigo due to different types of inner ear disease. The sound pressure levels ranged from 130 to 132 dB and were given at frequencies of 25, 50, and 63 Hz. The duration of each stimulation lasted 30 seconds. The postural responses were measured with a force platform. The LFS stimulation improved the postural stability of the healthy subjects through the alerting response. We did not observe any difference in the body sway according to whether the LFS was delivered with monaural or binaural stimulation. Twenty-six percent of the patients with Meniere's disease, 40% with chronic otitis media with vertigo, and 26% with vertigo of peripheral origin experienced significant postural instability at least at two of the three test frequencies during stimulation with LFS. The results demonstrate that in subjects with different types of inner ear disease the vestibular system starts to respond to LFS. The activation of vestibulospinal responses by LFS seems to be an expression of the Tullio phenomenon.

Effect of sleep on memory for binding different types of visual information

2020 ◽  
Author(s):  
John J Shaw ◽  
Zhisen Urgolites ◽  
Padraic Monaghan
Keyword(s):  
Visual Information ◽  
Storage Capacity ◽  
Declarative Memory ◽  
Recognition Task ◽  
Forced Choice ◽  
Long Term Memory ◽  
Term Memory ◽  
Different Types ◽  
Types Of Information

Visual long-term memory has a large and detailed storage capacity for individual scenes, objects, and actions. However, memory for combinations of actions and scenes is poorer, suggesting difficulty in binding this information together. Sleep can enhance declarative memory of information, but whether sleep can also boost memory for binding information and whether the effect is general across different types of information is not yet known. Experiments 1 to 3 tested effects of sleep on binding actions and scenes, and Experiments 4 and 5 tested binding of objects and scenes. Participants viewed composites and were tested 12-hours later after a delay consisting of sleep (9pm-9am) or wake (9am-9pm), on an alternative forced choice recognition task. For action-scene composites, memory was relatively poor with no significant effect of sleep. For object-scene composites sleep did improve memory. Sleep can promote binding in memory, depending on the type of information to be combined.

scholarly journals Performance of Norton Quantum Grinding Wheels

2016 ◽  
Vol 686 ◽  
pp. 125-130 ◽  
Author(s):  
Miroslav Neslušan ◽  
Jitka Baďurová ◽  
Anna Mičietová ◽  
Maria Čiliková
Keyword(s):  
Surface Roughness ◽  
Ground Surface ◽  
Bearing Steel ◽  
Grinding Wheel ◽  
Grinding Wheels ◽  
Grinding Forces ◽  
Removal Rates ◽  
Surface Burn ◽  
Conventional Grinding

This paper deals with cutting ability of progressive Norton Quantum grinding wheel during grinding roll bearing steel 100Cr6 of hardness 61 HRC. Cutting ability of this wheel is compared with conventional grinding wheel and based on measurement of grinding forces as well as surface roughness. Results of experiments show that Norton Quantum grinding wheels are capable of long term grinding cycles at high removal rates without unacceptable occurrence of grinding chatter and surface burn whereas application of conventional wheel can produce excessive vibration and remarkable temper colouring of ground surface. Moreover, while Norton Quantum grinding wheel gives nearly constant grinding forces and surface roughness within ground length at higher removal rates, conventional grinding wheel (as that reported in this study) does not.

scholarly journals A Comparison of Postural Responses in a Virtual and a Real Environment, a Randomised Controlled Study.

2021 ◽  
Author(s):  
Patrice Piette ◽  
Emilie Le Blong ◽  
Maxime Gilliaux ◽  
Mathilde Collet ◽  
Romain Cavagna ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Ethical Issues ◽  
Controlled Study ◽  
Functional Rehabilitation ◽  
Dynamic Surface ◽  
The Real ◽  
Repeated Measures Design ◽  
Centre Of Gravity ◽  
Balance Tests ◽  
Postural Responses

Abstract BackgroundImmersive virtual reality solutions are seeing increasing usage in functional rehabilitation programmes. However, there is no reference that allows us to confirm that these environments present the same characteristics and therefore the same degree of safety and training in postural responses for balance.QuestionThe aim of the study was to compare displacements from centre of gravity (distance covered and surface used) in balance tests, comparing the real situation to an identical virtual situation. Participants 70 healthy subjects aged between 18 and 65 were recruited in two centres. DesignThe study used a one-way repeated-measures design with randomisation of the order in which the two test conditions were performed. Intervention: .The first test condition was "real", taking place in a bedroom of a treatment centre apartment, and the second was virtual, with the room reproduced and seen through a HMD. For each condition, two static tests (left leg, right leg) and two dynamic tests (left and right) were performed. Each test included three attempts. Outcome measuresThe displacement from the centre of gravity was recorded on a force plate.Result69 participants completed all of the tests and were analysed. None of the tests resulted in confirmation that the virtual was equivalent to the real (Two One-Sided Tests for left static, right static, left dynamic, right dynamic; surface respectively p = 0.592, p = 0.151, p = 0.238, p = 0.503; distance respectively p = 1.00, p = 0.91, p = 0.0742, p = 1.00). Furthermore 6 tests of out 8 showed a significant and considerable difference (surface respectively p = 0.00249, p = 0.0664, p = 0.0318, p = 0.00483; distance respectively p = 1.12 x 10-8, p = 5.27 x 10-5, p = 0.153, p = 2.55 x 10-9). ConclusionPostural responses were poorer in the immersive virtual environment, both on the static and dynamic balance tests. The offer of balance rehabilitation in immersive VR raises safety issues and consequently ethical issues that are as yet unresolved. Researchers must test solutions to correct this serious problem. Trial registration: The study is registered at the US National Institutes of Health (ClinicalTrials.gov) NCT04574726

scholarly journals Orchid Reintroduction Based on Seed Germination-Promoting Mycorrhizal Fungi Derived From Protocorms or Seedlings

2021 ◽  
Vol 12 ◽  
Author(s):  
Da-Ke Zhao ◽  
Marc-André Selosse ◽  
Limin Wu ◽  
Yan Luo ◽  
Shi-Cheng Shao ◽  
...  
Keyword(s):  
Seed Germination ◽  
Mycorrhizal Fungi ◽  
Essential Element ◽  
Ecological Factors ◽  
New Approach ◽  
Practical Procedure ◽  
In The Wild ◽  
Orchid Mycorrhizal Fungi ◽  
Ecological Specificity

Orchids are among the most endangered in the plant kingdom. Lack of endosperm in their seeds renders orchids to depend on nutrients provided by orchid mycorrhizal fungi (OMF) for seed germination and seedling formation in the wild. OMF that parasitize in germination seeds is an essential element for orchid seedling formation, which can also help orchid reintroduction. Considering the limitations of the previous orchid reintroduction technology based on seed germination-promoting OMF (sgOMF) sourced from orchid roots, an innovative approach is proposed here in which orchid seeds are directly co-sown with sgOMF carrying ecological specificity from protocorms/seedlings. Based on this principle, an integrative and practical procedure concerning related ecological factors is further raised for re-constructing long-term and self-sustained orchid populations. We believe that this new approach will benefit the reintroduction of endangered orchids in nature.

scholarly journals WHAT IS THE ROLE BODY SWAY DEVIATION AND BODY SWAY VELOCITY PLAY IN POSTURAL STABILITY IN OLDER ADULTS?

2013 ◽  
Vol 56 (3) ◽  
pp. 117-123 ◽  
Author(s):  
Jitka Jančová Všetečková ◽  
Nicholas Drey
Keyword(s):  
Older Adults ◽  
Postural Stability ◽  
Care Home ◽  
Cross Sectional Study ◽  
Body Sway ◽  
Centre Of Pressure ◽  
Cross Sectional ◽  
Physically Active ◽  
Surface Test ◽  
The University

This cross sectional study focused on how Postural Stability (PS) indicators: body sway deviation (BSD) and body sway velocity (BSV), change with age and their association with levels of social and physical activity. Observational study: 80 older adults (aged: 60–96) were purposefully recruited from two sources: the University of the Third Age (TAU) (n = 35) and a residential care home (CH) (n = 45). Differences in the indicators of PS, approximated through Centre of Pressure (COP) measurements, were assessed by the Romberg Stance Test (Test A) subsequently repeated on 10 cm foam surface (Test B), using a Kistler® Dynamometric Platform. The RCH Group was older, had higher BMI and was less socially and physically active, showed more body sway in all indicators compared to TAU group. For all participants body sway velocity (BSV) was significantly correlated with age. The strength of correlation of body sway deviation (BSD) with age was also significant but not as strong. The findings indicate in line with previous studies that deterioration in BSV is associated with poor PS more than deterioration in BSD.

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