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Biomedical subjects

J R Lackner

Publications and source records attributed to J R Lackner.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1987

Treatment of severe motion sickness with antimotion sickness drug injections.

This report concerns the use of intramuscular injections of scopolamine, promethazine, and dramamine to treat severely motion sick individuals participating in parabolic flight experiments. The findings indicate that a majority of individuals received benefit from 50-mg injections of promethazine or 0.5mg-injections of scopolamine. By contrast, 50-mg injections of dramamine and 25-mg injections of promethazine were nonbeneficial. The use of antimotion drug injections for treating space motion sickness is discussed.

Dimenhydrinate↗
PubMed1987

Head movements in low and high gravitoinertial force environments elicit motion sickness: implications for space motion sickness.

Astronauts report that head movements in flight tend to bring on symptoms of space motion sickness (SMS). We evaluated how head movements in pitch, yaw, and roll--made both with normal vision and eyes-occluded--affect susceptibility to motion sickness in the zero G phase of parabolic flight maneuvers. The findings are clearcut: pitch head movements are most provocative, yaw least provocative, and roll intermediate. Susceptibility is greater with normal vision than with eyes occluded. The same susceptibility pattern emerged for head movements in the 1.8-2.0 G phase of parabolic flight. These experiments suggest that SMS is not a unique nosological entity but, rather, is the consequence of exposure to nonterrestrial force levels. Head movements during departures in either direction from 1 G elicit symptoms. This implies that, rather than speaking of "space motion sickness," it would be more appropriate to think in terms of "nonterrestrial motion sickness."

Gravitation↗
PubMed1987

The influence of gravitoinertial force level on oculomotor and perceptual responses to Coriolis, cross-coupling stimulation.

Susceptibility to motion sickness during exposure to constant levels of Coriolis, cross-coupling stimulation is lower in zero G and higher in 1.8 G than in a 1-G force environment (10, 13). The goal of the present experiment was to determine whether gravitoinertial force magnitude also influences oculomotor and perceptual responses to Coriolis, cross-coupling stimulation. We had blind-folded subjects who were rotating at constant velocity make standardized head movements during the free-fall and high force phases of parabolic flight, and we measured both the characteristics of their horizontal nystagmus and the magnitude of their experienced self-motion. Both responses were less intense in the free-fall periods than in the high force periods. Although the slow phase velocity of nystagmus reached the same initial, peak level in both conditions, it decayed more quickly in zero G. These findings suggest that the response to semicircular canal stimulation depends on the background level of gravitoinertial force.

Adult↗
PubMed1987

The influence of gravitoinertial force level on oculomotor and perceptual responses to sudden stop stimulation.

Our goal was to determine whether the vestibular response to vertical, z-axis body rotation in the dark is influenced by the magnitude of gravitoinertial force. We measured the nystagmus and the duration of illusory self-motion elicited in blindfolded subjects by cessation of such rotation during the free-fall, high, and terrestrial force phases of parabolic flight maneuvers. Both measures were significantly lower in zero G than in 1 G, and lower to a smaller extent in 1.8 G. The decreased intensity of nystagmus was due specifically to a decrease in the time constant of slow phase velocity decay with no decrement in peak velocity. This pattern of findings is consistent with the responses we had observed earlier to constant levels of Coriolis, cross-coupled stimulation during parabolic flight maneuvers both in terms of the mode of nystagmus suppression and the effect of G-level. Attenuation of the vestibular response to rotary acceleration in free-fall causes sensory-motor mismatches during natural head movements in orbital flight that may be important factors in the evocation of space motion sickness.

Coriolis Force↗
PubMed1986

The effective intensity of Coriolis, cross-coupling stimulation is gravitoinertial force dependent: implications for space motion sickness.

Coriolis, cross-coupled angular acceleration stimulation readily induces motion sickness under terrestrial conditions. Nevertheless, the Skylab astronauts, when tested with such stimulation in-flight, were insusceptible even though each had been susceptible pre-flight. It is unclear whether this decreased susceptibility was the consequence of in-flight adaptation or in part the result of immediate changes in sensory-motor and vestibulo-motor function that occur during exposure to microgravity conditions. To evaluate this issue, we have tested individuals both in the high and low force phases of parabolic flight maneuvers using constant levels of Coriolis, cross-coupled stimulation. Our findings indicate that 1.) subjects are less susceptible when tested in 0 G than +2 Gz; 2.) the perceived intensity and provocativeness of Coriolis stimulation decreases in 0 G and increases in +2 Gz relative to +1 Gz baseline values; and 3.) changes in the apparent intensity of Coriolis stimulation occur virtually immediately when background gravitoinertial force level is varied. These findings explain in large part why the Skylab astronauts were refractory to motion sickness during Coriolis stimulation in-flight. The general implications for space motion sickness are discussed.

Coriolis Force↗
PubMed1986

Sudden emesis following parabolic flight maneuvers: implications for space motion sickness.

Episodes of emesis unaccompanied by the usual prodromal signs of motion sickness have been reported by astronauts in the space shuttle program (10). Such reports have raised the issue whether space motion sickness has different characteristics from terrestrial motion sickness. We present evidence here from parabolic flight experiments that sudden vomiting can occur in response to a provocative vestibular stimulus even when no premonitory symptoms are being experienced. Accordingly, in chronic exposure conditions, the absence of prominent signs or symptoms of motion sickness does not necessarily mean an absence of sensitization.

Aerospace Medicine↗
PubMed1986

Head movements in non-terrestrial force environments elicit motion sickness: implications for the etiology of space motion sickness.

Space motion sickness has become an operational concern in manned space flight. Considerable evidence exists that head movements in free fall, especially pitch movements, are provocative until adaptation occurs (3,4,8,9,11,17,18,22,26). The question arises whether space motion sickness is an unique nosological entity or is due to body movements in a nonterrestrial force environment, a force environment for which the body's dynamic sensory-motor adaptions to 1 G are no longer appropriate (14,16,18-21). To evaluate this issue, we had subjects make controlled head movements during exposure to high gravitoinertial force levels, 1.8-2.0 G, in parabolic flight maneuvers. Head movements in pitch with eyes open were most evocative of motion sickness, yaw movements with eyes covered were least provocative. This pattern is identical to that which occurs when the same types of head movements are made in the free fall phase of parabolic maneuvers (17,18). It appears that space motion sickness is the consequence of prolonged exposure to a non-terrestrial force background rather than of exposure to free fall per se.

Adult↗
PubMed1985

Proprioceptive influences on auditory and visual spatial localization.

We evaluated the influence of proprioceptive information about arm position on the perceptual localization of auditory and visual targets attached to the hand. Our approach was to distort the perceived position of the restrained arm by means of mechanical vibration of the biceps brachii muscle; such vibration elicits compelling apparent extension of the stationary forearm (Goodwin, G. M., D. I. McCloskey, and P. B. C. Matthews (1972) Science 175: 1382-1384, Brain 95: 705-748), and subjects report changes in the apparent directions of the auditory and visual targets attached to their hand. These changes are in the same direction and plane as apparent arm motion and their onsets are coincident with or lag slightly behind the experienced displacement of the arm. While visual motion is being experienced, a subject's eyes remain steadily fixating the target light. The pattern of findings demonstrates that proprioceptive information about limb position can influence the central representation of gaze and auditory localization can be similarly influenced. The biasing of auditory localization indicates that identical patterns of arrival time and intensity cues at the two ears can give rise to the perception of sounds in widely disparate spatial positions in relation to the head and body, depending on the proprioceptive representation of the direction of the sound source.

Adolescent↗
PubMed1984

Influence of vision on vibration-induced illusions of limb movement.

Illusory motion of the unseen stationary forearm can be elicited by vibration of the biceps brachii or triceps brachii muscle. We have studied in 12 individuals how sight of part of the arm alone or in relation to other objects affects such vibration-induced, illusory motion of the forearm. Our findings indicate a complex but systematic influence of vision in attenuating apparent motion of the forearm. They show, too, that the seen and felt positions of the forearm can be dissociated and that physically impossible spatial configurations of the arm can be experienced. These findings have implications for physiological theories of position sense.

Eye Movements↗
PubMed1984

Some influences of tonic vibration reflexes on the position sense of the contralateral limb.

Mechanically vibrating a skeletal muscle elicits reflex activation of that muscle, a phenomenon which is known as the tonic vibration reflex. We explored in eight individuals how vibration of their right biceps brachii or triceps brachii muscle influenced their ability to point with their left arm to visual targets and to set that arm to particular apparent positions. The position sense of the pointing arm was affected systematically by contralateral vibration with the influence being considerably greater when the biceps brachii rather than the triceps brachii of the contralateral arm was stimulated. This asymmetric effect was related to the different densities of muscle spindle innervation of the biceps brachii and triceps brachii muscles and to their patterns of reflex organization within the spinal cord. The altered position sense of the pointing arm led to errors both for pointing movements with the arm to visual targets and for positioning movements of the arm into specified spatial configurations.

Adult↗
PubMed1984

Perception of body weight and body mass at twice earth-gravity acceleration levels.

On Earth, when standing on two feet, we experience particular patterns of force and pressure on the soles of our feet. As we lift one foot and balance on the other, little or no increase in force or pressure is perceived on the sole of the stance foot even though the contact forces of support on that foot have doubled. The failure to perceive this increase is actually an illusion resulting from the operation of spatial constancy mechanisms serving to preserve feelings of near constant force and pressure on the support surface(s) of the body. On Earth, body weight and body mass are perceived as remaining constant regardless as to whether we are standing on two feet or one and whether we are carrying large objects. In the high force phase(2 g acceleration) of parabolic flight, body weight is perceived as doubling, and a great increase in force is perceived on the soles of our feet if we are standing. When shifting balance from two feet to one, an increase in force of approximately 0.5 mg is felt on the sole of the stance foot. The actual increase in force is 1.0 mg but perceptual compensation is only being made for a 0.5 mg increase such as would be characteristic of shifting balance on Earth; accordingly an additional 0.5 mg (1.0-0.5 mg) residue is perceived. These findings indicate that body weight is dependent on the magnitude of the gravitoinertial forces acting on the body. Variations in the contact forces supporting the body due to passive or active locomotion of the body or to objects that are being carried are monitored and disregarded in computing apparent body weight. When stepping up and down from a low platform during the high force phases of parabolic flight, aberrant motion of the body and the aircraft is experienced. These illusory motions result because the doubling of body weight in a 2 g force background alters the normal relationship between patterns of alpha and gamma activation of antigravity muscles, muscle spindle activity, and the movements of the body. Accordingly, sensory-motor control and perceptual and postural stability on Earth are dependent on an active calibration to a 1 g background force level.

Acceleration↗
PubMed1984

Elicitation of motion sickness by head movements in the microgravity phase of parabolic flight maneuvers.

During parabolic flight maneuvers in a Boeing KC-135 aircraft 44 college students were tested for motion sickness susceptibility. These subjects were categorized as 1) insusceptible, 2) moderately susceptible, or 3) highly susceptible to motion sickness during exposure to varying gravitoinertial force levels. After categorization, they were tested in the microgravity phase of parabolic flight to see how three types of head movements affected their baseline susceptibility. The head movements evaluated included side-to-side swivel, shoulder-to-shoulder roll, and front-up head and trunk movements; each type of head movement was used on a separate test day for eyes-open and eyes-covered conditions. Ten cycles of head movements were made in each parabola until a motion sickness endpoint, nausea, was reached or 40 parabolas had been completed. All types of head movements significantly increased susceptibility for subjects in all categories; eyes-open conditions were always more stressful than eyes-closed for each kind of head movement. These findings show unequivocally that natural head movements in microgravity can elicit symptoms of motion sickness. They suggest that head movements play an important etiological role in space motion sickness. In ground based studies where head movements are necessary to elicit symptoms, they are also necessary to elicit adaptation. We describe the use of paced and incremented head movement schedules as a possible way of partially alleviating space motion sickness.

Aerospace Medicine↗
PubMed1983

Etiological factors in space motion sickness.

We compared susceptibility to motion sickness during exposure to sudden-stop stimulation as a function of gravitoinertial force level. Our findings show that susceptibility is greatly enhanced, both with eyes-closed and eyes-open, for zero-g and 2-g conditions in parabolic flight compared with 1-g test conditions. The change in susceptibility is likely related to three factors: alterations in vestibulo-ocular function which result from variations in gravitoinertial force level (28,29); the altered pattern of otolithic activity resulting during variations in gravitoinertial force level; and the altered canal-otolith response synergies that result during exposure to gravitoinertial force levels greater or less than terrestrial levels. These factors are shown to be related to the etiology of space motion sickness and to the alterations in performance and vestibular function that are experienced by astronauts during reentry. An explanation is also proposed for the decrease in susceptibility to motion sickness exhibited by the Skylab astronauts inflight and for some period postflight during exposure to cross-coupled angular accelerations.

Adult↗
PubMed1983

Reciprocal interactions between the position sense representations of the two forearms.

Muscle spindle afferents are known to influence the conscious appreciation of limb position. If a limb muscle is mechanically vibrated while the limb is physically restrained from moving under the action of the resulting tonic vibration reflex, illusory motion of the limb will be experienced in the direction that would be associated with stretch of the vibrated muscle. Two experiments are presented that explore how grasping with the other hand the forearm of an arm whose biceps or triceps muscle is being vibrated affects the apparent position of the two arms. If the vibrated arm is grasped before the onset of vibration, then illusory motion of both arms is experienced during vibration. The magnitude of this apparent motion and displacement is less than that experienced when the vibrated arm is not held. If the vibrated arm is grasped after the onset of vibration and when illusory displacement is being experienced, then its apparent motion is suppressed and the grasping arm is correctly perceived as stationary. The existence of this reciprocal, position sense interaction between the two arms suggests that the conscious awareness of limb position is not dependent solely on afferent and efferent information about individual limbs in isolation, but potentially involves coordinating spatial information about the configuration of the entire body.

Adult↗
PubMed1983

Perceived orientation in free-fall depends on visual, postural, and architectural factors.

In orbital flight and in the free-fall phase of parabolic flight, feelings of inversion of self and spacecraft, or aircraft, are often experienced (2,3). We show here that perceived orientation in free-fall is dependent on the position of one's body in relation to the aircraft, the architectural features of the aircraft, and one's visual appreciation of the relative configurations of his body and the aircraft. Compelling changes in the apparent orientation of one's body and of the aircraft can be reliably and systematically induced by manipulating this relationship. Moreover, while free-floating in the absence of visual, touch, and pressure stimulation, all sense of orientation to the surroundings may be lost with only an awareness of the relative configuration of the body preserved (7). The absence of falling sensations during weightlessness points to the importance of visual and cognitive factors in eliciting such sensations.

Aerospace Medicine↗