Reference Stick Research Articles

The impact of gravity on perceived object height

Altering posture relative to the direction of gravity, or exposure to microgravity has been shown to affect many aspects of perception, including size perception. Our aims in this study were to investigate whether changes in posture and long-term exposure to microgravity bias the visual perception of object height and to test whether any such biases are accompanied by changes in precision. We also explored the possibility of sex/gender differences. Two cohorts of participants (12 astronauts and 20 controls, 50% women) varied the size of a virtual square in a simulated corridor until it was perceived to match a reference stick held in their hands. Astronauts performed the task before, twice during, and twice after an extended stay onboard the International Space Station. On Earth, they performed the task of sitting upright and lying supine. Earth-bound controls also completed the task five times with test sessions spaced similarly to the astronauts; to simulate the microgravity sessions on the ISS they lay supine. In contrast to earlier studies, we found no immediate effect of microgravity exposure on perceived object height. However, astronauts robustly underestimated the height of the square relative to the haptic reference and these estimates were significantly smaller 60 days or more after their return to Earth. No differences were found in the precision of the astronauts’ judgments. Controls underestimated the height of the square when supine relative to sitting in their first test session (simulating Pre-Flight) but not in later sessions. While these results are largely inconsistent with previous results in the literature, a posture-dependent effect of simulated eye height might provide a unifying explanation. We were unable to make any firm statements related to sex/gender differences. We conclude that no countermeasures are required to mitigate the acute effects of microgravity exposure on object height perception. However, space travelers should be warned about late-emerging and potentially long-lasting changes in this perceptual skill.

Video Motion Interpolation for Special Effect Applications

Video forgery, also referred as video falsifying, is a technique for generating fake videos by altering, combining, or creating new video contents. For instance, the outcome of a 100 m race in the olympic game is forged as an example in this paper. We track objects and segment motions using a modified mean shift mechanism. The resulting video layers can be played in different speeds and from different reference points with respect to the original video. In order to obtain a smooth movement of target objects, a motion interpolation mechanism is proposed based on reference stick figures (i.e., a structure of human skeleton) and a video inpainting mechanism. The video inpainting mechanism is performed in a quasi-3-D space via guided 3-D patch matching. Interpolated target objects and background layers are then fused. The objective is to create a forged video, which is almost indistinguishable from the original video. We demonstrate the original and the forged videos in our Web site at http://member.mine.tku.edu.tw/www/TSMC09/. Although video forgery may create moral or legal issues, which is beyond the scope of this paper, our intension is to create special effects in video editing applications.

Characteristics of sensing lower-jaw-position in patients with cerebral palsy during laughing gas-induced sedation

To clarify the effects of the applied during sedation with nitrous oxide (hereafter referred to as laughing gas) on the ability of muscles attached to the lower jaw to sense lower-jaw-position and on the sensation of muscle spindles attached to the lower jaw in patients with cerebral palsy (CP) using healthy adult subjects without functional abnormalities of the jaws and oral cavities as control subjects (hereafter referred to as healthy subjects). Experiments were performed under the following conditions: for each subject, before the inhalation of laughing gas (LG) and oxygen (air-inhalation condition: referred to as without LG inhalation) and during the inhalation of LG and oxygen (inhalation condition of LG and oxygen under LG-induced sedation: referred to as during LG inhalation). Subjects in the experiments were eight CP patients and eight healthy people as controls. The ability to discriminate lowerjaw- position was estimated by asking the subjects to determine whether the diameter of a test stick was larger or smaller than that of a reference stick after performing the following tasks: a) holding a reference stick between the central teeth of their upper and lower jaws for 5 s, and b) replacing the reference stick with a test stick and holding it at the same position for 5 s, and the test stick was then removed. The following findings were obtained. 1) In comparing discrimination ability in the absence of LG-induced sedation and that during LG-induced sedation of healthy control subjects, the rate of mis-estimation (RME) was significantly larger during LG-induced sedation than in the absence of LG-induced sedation for a test stick diameter (10.5 mm or 11.0 mm) larger than the reference stick diameter (10. 0mm) ( P < 0.05). No significant differences were observed for any other test sticks ( P > 0.05). 2) In comparing discrimination ability in the absence of LG-induced sedation and that during LG-induced sedation of CP patients, RME was significantly smaller during LG-induced sedation than in the absence of LG-induced sedation, when the test stick diameter (9.5 mm) was smaller than the reference stick diameter ( P < 0.05). No significant differences were observed for any other test sticks ( P > 0.05). These results indicate that neural functions are inhibited at the upper level of the central nervous system in CP patients, leading to the attenuation of sustained increase in muscle tonus that is characteristic of CP patients. In summary, it seems that the LG has some inhibitory effect on the activity of γ-motor neurons innervating muscle spindles attached to the lower jaw via the upper level of the central nervous system and that this inhibitory effect contributes to an improvement in the discrimination ability.

Effects of vibration stimulus on lower-jaw-position sensation in patients with cerebral palsy during inhalation of laughing gas

To clarify the effects of a vibration stimulus applied during sedation with nitrous oxide (hereafter referred to as laughing gas) on the ability of muscles attached to the lower jaw to sense lower-jaw position and on the sensation of muscle spindles attached to the lower jaw in patients with cerebral palsy (CP) using healthy adult subjects without functional abnormalities of the jaws and oral cavities as control subjects (hereafter referred to as healthy subjects). Experiments were performed under the following conditions: for each subject, before the application of the vibration stimulus (referred to as S pre ) and after the application of the vibration stimulus (S post ); before the inhalation of laughing gas (LG) and oxygen (air-inhalation condition: referred to as without LG inhalation) and during the inhalation of LG and oxygen (inhalation condition of LG and oxygen under LG-induced sedation: referred to as during LG inhalation). Subjects in the experiments were eight CP patients and eight healthy people as controls. The ability to discriminate lower-jaw position was estimated by asking the subjects to determine whether the diameter of a test stick was larger or smaller than that of a reference stick after performing the following tasks: a) holding a reference stick between the central teeth of their upper and lower jaws for 5 s, and b) replacing the reference stick with a test stick and holding it at the same position for 5 s, and the test stick was then removed. The following findings were obtained. 1) In comparing the ability of healthy subjects to discriminate between S pre and S post during LG inhalation using different test sticks, when the test stick diameter was 9.5 mm (smaller than the reference stick diameter), the rate of mis-estimation (RME) for Spost was significantly larger than that for Spre ( P < 0.05). No significant differences were observed for any other test sticks. 2) In comparing the ability of CP patients to discriminate between S pre and S post during LG inhalation using different test sticks, when the test stick diameter was 9.5 mm (smaller than the reference stick diameter), the RME for S post was significantly smaller than that for S pre ( P < 0.05). No significant differences were observed for any other test sticks. These results suggest the following: the combination of LG for sedation with vibration stimulus further inhibits neuronal functions at the upper level of the central nervous system in CP patients, compared with cases in which each variable is applied separately, and the combination also inhibits the sustained increase in muscle tonus, which is characteristic of CP patients. LG reduces the activity of γ-motor neurons via the upper level of the central nervous system. In addition, tonic vibration reflex (TVR) develops due to the vibration stimulus, which increases the threshold value of sensitive muscle sensation and decreases the activity of γ-motor neurons, and furthermore decreases the activity of muscle spindles attached to the lower jaw. Consequently, a tendency toward increased ability to discriminate lower-jaw position is observed.

Characteristics of lower-jaw-position sensation with respect to oral-jaw functions in patients with cerebral palsy

In order to investigate the effects of desensitization which is induced by the application of a vibration stimulus simulating massage to patients with cerebral palsy (CP) on the lower-jaw-position sensation, we compared the masticatory-muscle sensation of patients with CP with that of healthy adults without functional abnormalities of the jaw and oral cavity who were used as control subjects, using a lower-jaw-position sensation discrimination test. The subjects of the study were eight patients with CP and eight healthy adults as control subjects. The following findings were obtained. 1) When the discrimination ability in healthy adults was compared between before and after the stimulus application, it was significantly higher after the stimulus application when the interincisal distance was smaller (9.5 mm) than that with the reference stick. 2) When the discrimination ability of patients with CP was compared between before and after the stimulus application, it was significantly lower after the stimulus application when the interincisal distance was smaller (9.5 mm) than that with the reference stick. Thus, results for the patients with CP are contrary to those for healthy adults; this is because of the appearance of the tonic vibration reflex in CP patients, which results in a decrease in the activity of γ-motor neurons. The threshold value of muscle sensation was increased by the application of vibration stimulus. Consequently, the discrimination ability of the patients with CP increased.

The effect of maximal mouth opening on dimension discrimination.

The ability of twenty-five young persons to discriminate dimensions was tested. A reference stick of 10 mm was placed between the teeth, alternating with test sticks of different heights. After application of the reference stick the subjects were asked to open the mouth maximally. A test stick was placed on the lower incisors and the subjects closed the mouth slowly, until their upper incisors contacted the test stick. The subjects were then asked to assess whether a test stick felt higher or lower than the reference stick. Using this experimental method, it was found that incorrect assessments were symmetrically distributed around the 10 mm reference stick. A receptor mechanism is proposed, and applied to explain the results of the present and a previous experiment.

Dimension discrimination at two different degrees of mouth opening and the effect of anaesthesia applied to the periodontal ligaments

The dimension discrimination ability of twenty-five young persons was tested at two different degrees of mouth opening. One reference stick of 10-0 mm and another of 45-0 mm was placed between the teeth, alternating with test sticks of different heights. The subjects were asked to assess whether a test stick felt higher or lower than the reference stick. The experiment was performed with and without anaesthesia applied to the periodontal ligaments. Anaesthesia did not impair the discrimination ability. At dimensions in the region of the 10-0 mm stick the incorrect assessments occurred predominantly among sticks higher than the reference stick. Around the 45-0 mm stick incorrect assessments were distributed evenly between dimensions higher or lower than the reference stick.

Conditioning-effect of vibratory stimulation on dimension discrimination of objects held between human tooth arches

Dimension-discriminating ability of a mouth was tested with and without giving vibration to the mandible. The method was to compare a reference stick 10 mm thick, with test sticks of different dimension, and the subjects were asked whether the test stick was felt thicker or thinner than the reference. In the test without vibration, mis-estimates mainly occurred by judging thicker test sticks to be thinner than the reference. On the contrary, when the vibration was applied on the mandible before test stick application, mis-estimates mainly occurred by judging thinner test sticks to be thicker than the reference. Based on such post-vibratory change of dimension-discriminating ability, it is speculated that muscle spindles in the masticatory muscles contribute to this ability.

INACCURACY OF TEST STRIPS WITH REFLECTANCE METER IN DETERMINATION OF HIGH BLOOD-SUGARS

By recovery experiments and by determination of clinical blood-sugars six ' Dextrostix ' reflectance meters have been evaluated. From comparisons of this method with an ' Auto-Analyzer ' glucose-oxidase method it was demonstrated that most of these meters cannot accurately determine blood-sugar values above 180 mg. per 100 ml. and may be functionally unstable. It is recommended that each meter be individually tested by the producer and provided with a reference stick to the measuring scale for estimating blood-sugars from 180 to 1000 mg. per 100 ml.