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Biomedical subjects

K E Money

Publications and source records attributed to K E Money.

At least 19 recordsLinked to original sources
PubMed1995

Dynamics of torsional optokinetic nystagmus under altered gravitoinertial forces.

The purpose of the present study was to investigate the influence of varying gravitoinertial forces on torsional optokinetic nystagmus during parabolic flights. Using the scleral search-coil technique, we measured the gain and phase lag of torsional optokinetic nystagmus (OKN) induced by a hemispherical visual display rotating about the roll axis either at constant velocity or sinusoidally at various frequencies during level flight, hypogravity, and hypergravity. Compared with level flight, there was a significant increase in slow-phase eye velocity during hypogravity and an increase in nystagmic frequency. An absence of well-developed torsional optokinetic afternystagmus was observed in all three gravity conditions. Other characteristics included a lack of a slow rise component. These data suggest that otolith inputs do affect torsional optokinetic afternystagmus suggests that the velocity storage pathways do not contribute significantly to the torsional OKN system in humans.

Acceleration↗
PubMed1994

Etiologic significance of arginine vasopressin in motion sickness.

There is abundant evidence implicating the role of arginine vasopressin in motion sickness. The effects of AVP analogs on motion sickness were investigated in squirrel monkeys. Two specific V1 antagonists (SK&F 100273 and SK&F 103561) and three mixed V1/V2 antagonists (SK&F 101926, SK&F 105494, and SK&F 104146-D) were tested on six highly susceptible monkeys. Intravenous injections of 200 ug of a V1 antagonist abolished emesis in all six monkeys, and few prodromal symptoms remained (latency to emesis > 120 minutes, P < .001). Mixed V1/V2 antagonists failed to abolish emesis in all monkeys. However, there was a slight increase in the latency to the first bout of emesis/retching with the mixed antagonists when compared with the baseline. The dose-response relationship and rate of onset of action of the V1 antagonists (SK&F 100273) were explored. Latency to the first bout of emesis/retching increased to about twice that of the baseline when half of the effective antiemetic dose was used. The efficacy demonstrated by the specific V1 antagonists indicates that V1 receptors may modulate emesis.

Animals↗
PubMed1994

Human gaze instability during brief exposure to reduced gravity.

The stability of gaze in three dimensions (horizontal, vertical and torsional) was investigated with the electromagnetic scleral search-coil technique during the microgravity phase of parabolic flights under two visual fixation conditions: fixation on a real target and on an imagined target. Subjects were secured upright with the head immobilized by a dental bite. There were torsional eye movements in response to the imposition of reduced gravitoinertial forces under both visual fixation conditions. The pattern of these movements was consistent with our previous findings on six other subjects. No significant horizontal eye movements were observed in either fixation condition. Under the condition of fixation on an imagined target, direction-specific vertical nystagmus was observed with slow phase directed upwards during transition from hypergravity to microgravity. The slow phase was directed downwards during transition from microgravity to hypergravity, although the nystagmus was of lower frequency and the magnitude of the slow phase velocity appeared to be smaller than during transition from hypergravity to microgravity. The vertical eye movements could be attributed to a change of otolithic stimulation along the subject's z axis since the rate of pitch rotation of the aircraft during parabolic flight was too slow to produce an effective canal input. These kinds of reflex eye movements could degrade vision during manoeuvres or turbulence in flight.

Adult↗
PubMed1992

Investigation of anti-motion sickness drugs in the squirrel monkey.

Early attempts to develop an animal model for anti-motion sickness drugs, using dogs and cats; were unsuccessful. Dogs did not show a beneficial effect of scopolamine (probably the best single anti-motion sickness drug for humans thus far) and the findings in cats were not definitive. The authors have developed an animal model using the squirrel monkey (Saimiri sciureus) of the Bolivian phenotype. Unrestrained monkeys in a small lucite cage were tested in an apparatus that induces motion sickness by combining vertical oscillation and horizontal rotation in a visually unrestricted laboratory environment. Signs of motion sickness were scored using a rating scale. Ten susceptible monkeys (weighing 800-1000 g) were given a total of five tests each, to establish the baseline susceptibility level. Based on the anticholinergic activity of scopolamine, the sensitivity of squirrel monkey to scopolamine was investigated, and the appropriate dose of scopolamine for this species was determined. Then various anti-motion sickness preparations were administered in subsequent tests: 100 ug scopolamine per monkey; 140 ug dexedrine; 50 ug scopolamine plus 70 ug dexedrine; 100 ug scopolamine plus 140 ug dexedrine; 3 mg promethazine; 3 mg promethazine plus 3 mg ephedrine. All these preparations were significantly effective in preventing motion sickness in the monkeys. Ephedrine, by itself, which is marginally effective in humans, was ineffective in the monkeys at the doses tried (0.3-6.0 mg). The squirrel monkey appears to be a good animal model for antimotion sickness drugs. Peripherally acting antihistamines such as astemizole and terfenadine were found to be ineffective, whereas flunarizine, and an arginine vasopressin V1 antagonist, showed significant activity in preventing motion sickness.

Animals↗
PubMed1992

The influence of age on susceptibility to motion sickness in monkeys.

A longitudinal study on the effects of age on the susceptibility to motion sickness in the squirrel monkey was carried out over a 10-year period (1982 to 1991). The typical life span of squirrel monkeys is 15 years. Ten mature male squirrel monkeys of the Bolivian subspecies were found to be susceptible to motion sickness induced by a combination of vertical oscillation at 0.5 Hz and rotation in the horizontal plane at 25 rotations per minute (RPM) in a visually unrestricted environment. Signs of motion sickness were quantified according to a rating scale based on Graybiel's diagnostic criteria. Latency to vomiting/retching and severity of sickness obtained from year 1 (baseline), 3, 5, 7 and 10 were subjected to repeated-measures design analysis. There were no significant differences in the susceptibility level (as measured by latency to vomiting/retching and cumulative sickness scores) in the monkeys throughout the 10-year period. The habituation to 7 consecutive daily exposures remained the same throughout the same period. We conclude that, in the squirrel monkeys from maturity to near the end of their life span, there is no change in susceptibility to motion sickness with aging.

Aging↗
PubMed1992

Accuracy of aimed arm movements in changed gravity.

We studied the accuracy of aimed arm movements in normal gravity, and during the hypergravity (hyper-G) and microgravity (micro-G) episodes of KC-135 parabolic flights. Subjects pointed at mirror-viewed targets without sight of their arm, and final pointing position was measured by a digitizing pad. Compared with the normal gravity (normal-G) baseline, subjects pointed consistently higher in hyper-G, and still higher in micro-G. Results were not different if subjects viewed targets only during normal-G and pointed at their memorized position under changed gravity (changed-G); this suggests that the "elevator illusion" played a minor role in our study. The observed impairments were attributed to degraded proprioceptive feedback and/or inappropriate motor programs in changed-G. Pointing accuracy improved movement-to-movement but not parabola-to-parabola, indicating that prolonged exposure is needed for sustained adaptation.

Aerospace Medicine↗
PubMed1991

Visually-induced sickness in normal and bilaterally labyrinthine-defective subjects.

A group of nine normal subjects (with no overt vestibular dysfunction) and a group of 6 bilaterally labyrinthine-defective subjects were exposed to a visual field rotating about an Earth-horizontal axis (orthogonal to the gravity axis). The visual stimulus was provided by a 3-m diameter sphere with random dots rotating at 30, 45, and 60 degrees per second (degree/s) about the stationary subject's roll, pitch and yaw axes. The subject's head was positioned at the center of the sphere such that it experienced apparent motion in all three axes. Results indicated that in the normal group, symptoms of motion sickness were reported in 21 of 27 test-trials. When labyrinthine-defective subjects were exposed to the roll and pitch stimulus, no sickness symptoms were reported or observed. These results strongly suggest that the vestibular system is necessary for sickness induced by moving visual fields.

Adult↗
PubMed1990

Visually-induced tilt during parabolic flights.

A helmet-mounted visual display system was used to study visually induced sensations of self-motion (vection) about the roll, pitch and yaw axes under normal gravity condition (1g) and during the microgravity and hypergravity phases of parabolic flights aboard the NASA KC-135 aircraft. Under each gravity condition, the following parameters were investigated: (1) the subject's perceived body vertical with eyes closed and with eyes open gazing at a stationary random dot display; (2) the magnitude of sensations of body tilt with respect to the subjective vertical, while the subject viewed displays rotating about the roll, pitch and yaw axes; (3) the magnitude of vection; (4) latency of vection. All eleven subjects perceived a definite "up and down" orientation throughout the course of the flight. During the microgravity phase, the average magnitudes of perceived body tilt and self-motion increased significantly, and there was no significant difference in vection latency. These results show that there is a rapid onset of increased dependence on visual inputs for perception of self-orientation and self-motion in weightlessness, and a decreased dependence on otolithic and somatosensory graviceptive information. Anti-motion sickness drugs appear not to affect the parameters measured.

Aerospace Medicine↗
PubMed1990

Motion sickness susceptibility and aerobic fitness: a longitudinal study.

A longitudinal study evaluated the susceptibility to motion sickness in initially unfit subjects before and after an endurance training program. Motion stimulation was provided by the Precision Angular Mover, in which the subject was tumbled head over heels about an Earth-horizontal axis at 20 cycles per minute in darkness. Maximal aerobic power and the blood lactate response to submaximal exercise were evaluated with cycle ergometry. The training program caused significant improvements in VO2max and endurance capacity, and a significant decrease in percent body fat. There was a significant (p less than 0.0125) increase in motion sickness susceptibility after the physical training, suggesting that increased physical fitness caused increased susceptibility to motion sickness in some individuals.

Adrenocorticotropic Hormone↗
PubMed1990

Instability of ocular torsion in zero gravity: possible implications for space motion sickness.

Inherent asymmetries of the gravity-sensitive otolith organs of the inner ear may be well-compensated in ordinary 1 G, but rendered unstable in novel gravitational states. Several aspects of ocular counterrolling and spontaneous eye torsion, reflexes governed by the otoliths, were examined during the hypo- and hypergravity in parabolic flight on the NASA KC-135 aircraft. Among the subjects were two astronauts, one who had suffered space motion sickness during his mission and one who had not. Using an observed separation of scores of torsional instability at 0 G as the criterion, we divided our 10 subjects into the 5 highest and 5 lowest scorers, reminiscent of the approximately 50% who do and the 50% who do not experience space motion sickness (SMS). The astronaut who had had SMS was in the high group; and the one who had not was in the low group. At 1.8 G, the groups defined at 0 G were significantly different in the instability measure. They were also significantly different at both 0 G and 1.8 G in another measure, that of torsional variability. There were no differences between the groups in amplitude of eye torsion in 0 G or 1.8 G. None of the tests were significantly different in 1 G. The results suggest that these tests of eye torsion on the KC-135 might differentiate those who would experience SMS from those who would not. Proof of this speculation awaits replication of the study using only astronaut subjects.

Gravitation↗
PubMed1987

An illusion of reversed direction in hyperopes.

If a subject who is sufficiently farsighted removes his corrective, positive, lenses and looks with one eye from a distance of one or a few meters, at a small lighted area such as the (continuously "on") indicator light of an electric toothbrush, razor, or smoke detector, and if a small object such as a pin is then moved slowly from above to below the subject's eyes (in a plane close to the eye), the subject will perceive the object moving normally from above to below until it encroaches on his view of the lighted area. The object will then be seen to encroach first on the bottom of the lighted area, and as the object continues to move down it will be seen to be moving up across the lighted area, exiting the lighted area at the top. Similarly, an object moved in front of the eye from the subject's left to his right will be seen by the subject to traverse the lighted area in the reverse direction, right to left, even though the subject moves the object himself. Also, while the object is in front of the lighted area, it is perceived as an upside down silhouette having surprisingly clear and sharp edges, and it appears to be located on the lighted area rather than close to the eye where it really is.

Form Perception↗
PubMed1987

Asymmetric otolith function and increased susceptibility to motion sickness during exposure to variations in gravitoinertial acceleration level.

Von Baumgarten and his colleagues (23,24) have suggested that asymmetries in otolith function between the left and right labyrinths may result from differences in otoconial mass and could play a role in space motion sickness. Such asymmetries would be centrally compensated for under terrestrial conditions but on exposure to weightlessness the persisting central compensation would produce a central imbalance that could lead to motion sickness. We have used ocular counterrolling as a way of measuring the relative "efficiency" of the left and right otoliths and have compared the ocular counterrolling scores of individuals with their susceptibility to motion sickness during passive exposure to variations in Gz in parabolic flight maneuvers. The experimental findings indicate that large asymmetries in counterrolling for leftward and rightward body tilts are associated with greater susceptibility to motion sickness in parabolic flight.

Acceleration↗
PubMed1986

M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 1. Sensory adaptation to weightlessness and readaptation to one-g: an overview.

Experiments on human spatial orientation were conducted on four crewmembers of Space Shuttle Spacelab Mission 1. This introductory paper presents the conceptual background of the project, the relationship among the experiments and their relevance to a "sensory reinterpretation hypothesis". Detailed experiment procedures and results are presented in the accompanying papers in this series. The overall findings are discussed in this article as they pertain to the following aspects of hypothesized sensory reinterpretation in weightlessness: utricular otolith afferent signals are reinterpreted as indicating head translation rather than tilt, sensitivity of reflex responses to footward acceleration is reduced, and increased weighting is given to visual and tactile cues in orientation perception and posture control. Three subjects developed space motion sickness symptoms, which abated after several days. Head movements, as well as visual and tactile cues to orientation influenced symptoms in a manner consistent with the sensory-motor conflict theory of space motion sickness. Six short duration tests of motion sickness susceptibility, conducted pre-flight, failed to predict sickness intensity in weightlessness. An early otolith-spinal reflex, measured by electromyography from the gastrocnemius-soleus muscles during sudden footward acceleration, was inhibited immediately upon entering weightlessness and declined further during the flight, but was unchanged from pre-flight when measured shortly after return to earth. Dynamic visual-vestibular interaction was studied by measuring subjective roll self-motion created by looking into a spinning drum. Results suggest increased weighting of visual cues and reduced weighting of graviceptor signals in weightlessness. Following the 10 day flight, erect posture with eyes closed was disturbed for several days.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1986

M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 3. Effects of prolonged weightlessness on a human otolith-spinal reflex.

Reflex responses that depend on human otolith organ sensitivity were measured before, during and after a 10 day space flight. Otolith-spinal reflexes were elicited by means of sudden, unexpected falls. In weightlessness, "falls" were achieved using elastic cords running from a torso harness to the floor. Electromyographic (EMG) activity was recorded from gastrocnemius-soleus. The EMG response occurring in the first 100-120 ms of a fall, considered to be predominantly otolith-spinal in origin, decreased in amplitude immediately upon entering weightlessness, and continued to decline throughout the flight, especially during the first two mission days. The response returned to normal before the first post-flight testing session. The results suggest that information coming from the otolith organs is gradually ignored by the nervous system during prolonged space flight, although the possibility that otolith-spinal reflexes are decreased independent of other otolith output pathways cannot be ruled out.

Adaptation, Physiological↗
PubMed1986

M.I.T./Canadian vestibular experiments on the Spacelab-1 mission: 4. Space motion sickness: symptoms, stimuli, and predictability.

Space sickness symptoms were observed by 4 specially trained observers on Spacelab-1. Three reported persistent symptoms, and vomited repeatedly during the first and/or second day of flight. Head movements on all axes were provocative, particularly in pitch and roll. Head acceleration data recorded from 2 symptomatic crewmen showed that after several hours of physical activity in orbit, symptoms appeared, and thereafter both crewmen were compelled to limit head movements. Firm body contact with motionless surfaces helped alleviate symptoms. When crewmembers floated into unfamiliar body orientations in the cabin, inherent ambiguities in static visual orientation cues sometimes produced spatial reorientation episodes which were also provocative. Symptoms largely resembled those of other forms of prolonged motion sickness, superimposed upon other symptoms attributable to fluid shift. All 4 eventually used anti-motion sickness drugs. When they did, vomiting frequency was reduced. By the 4th day, symptoms subsided, and head accelerations again increased in magnitude and variability. Sickness intensity in orbit was not predicted by statistically concordant results of 6 acute preflight susceptibility tests. However, results from a longer duration preflight prism goggles test showed an apparent correlation. All subjects were asymptomatic making head movements in parabolic flight 4 days after the mission, but not 1 year later. Overall, results support the view that space sickness is a motion sickness.

Acceleration↗
PubMed1986

Effect of head tilt on visual cortical cell function in the intact and labyrinthectomized cat.

The area of the receptive field, its length and width, its position in the visual field, the peristimulus time (PST) histogram (i.e., the response to successive moving light-bar stimuli), the directional preference, the velocity gradient, and the intertrial (spontaneous) firing rate were studied electrophysiologically in complex cortical visual cells in Brodmann's area 18. These characteristics were explored after head tilt, in immobilized cats, both in intact and in bilaterally labyrinthectomized animals. In intact animals (in 64 cells), most of these characteristics changed after head tilts of 10, 20, 30, or 40 degrees to the right or to the left of the horizontal plane. There was always one specific head position in which the receptive field area was at its smallest. In labyrinthectomized animals (in 29 cells), the lengths, widths, and the areas of the receptive fields were only minimally altered during identical tilts. Similarly, in the labyrinthectomized cats, head tilts (40 degrees, to the right or left) caused no substantial changes in the shape and duration of the PST histogram, compared with those in intact cats. No two visual cortical cells responded to head tilts in exactly the same manner. Such uniqueness in response is probably of importance during visual image analysis; in particular, as it relates to cortical reconstruction of stable visual images during continuously changing head movements and positions.

Animals↗