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Biomedical subjects

J R Lackner

Publications and source records attributed to J R Lackner.

At least 91 records · Page 5Linked to original sources
PubMed1983

Motion sickness: acquisition and retention of adaptation effects compared in three motion environments.

A sharp distinction should be made between symptoms of motion-sickness per se and phenomena inferred from the symptomatology, which include rates of acquisition and decay of adaptation effects. Foreknowledge of these "derived phenomena" are valuable if it can be shown that they hold true for virtually any motion environment. Recently, we have developed a sudden-stop vestibulovisual interaction test for measuring susceptibility to motion sickness (1). The test procedure involves four successive assessments that provide not only an index of susceptibility to motion sickness but also the rates of acquisition and decay of adaptation effects. The 14 subjects participating in this test had previously served as subjects in parabolic flight experiments and seven of them had also taken part in the assessment of antimotion-sickness remedies in a slow rotation room. The present report examines whether their rates of acquisition and decay of adaptation to stressful motion represent consistent general features of their responses across motion environments. From these comparisons, it appears that an individual's rates of acquiring and losing adaptation are quite consistent in very different situations. The pattern of results also suggests modifications of the sudden-stop vestibulovisual test that should increase its effectiveness as a motion-sickness screening procedure, both for orbital flight and for terrestrial conditions.

Adaptation, Biological↗
PubMed1982

Alterations in speech shadowing ability after cerebral injury in man.

Patients with penetrating wounds of the left cerebral hemisphere are inferior to normal control subjects and patients with right hemisphere lesions in their ability to shadow language stimuli presented at various rates. Their performance deteriorates rapidly at higher rates of stimulus presentation. Patients with bilateral cerebral penetration show similar patterns of deficits. The deficits on the shadowing task are especially prominent in patients who were dysphasic or dysarthric during the immediate postinjury period.

Aphasia↗
PubMed1982

Alterations in resolution of linguistic ambiguity after cerebral injury in man.

The present experiment examined the ability of subjects with penetrating brain injuries to resolve different forms of linguistic ambiguity. Most subjects with penetrating head wounds of the left cerebral hemisphere (n = 11) had impaired ability to detect linguistic ambiguity even when tested 20 yr. after injury. This decrement in performance was present for all types of ambiguity and was most pronounced in subjects who were dysphasic post-injury (n = 7). A similar pattern was shown by patients with bilateral cortical penetration (n = 11), especially those who were dysarthric or dysphasic (n = 5) immediately after injury. Performance on phonetic and underlying constituent structure ambiguities was more severely affected than performance on lexical, derived constituent structure, and particle-preposition ambiguities. By contrast, patients with right-penetrating cortical lesions (n = 18) performed nearly as well as the normal control subjects (n = 12).

Adult↗
PubMed1982

Rapid perceptual adaptation to high gravitoinertial force levels: evidence for context-specific adaptation.

Subjects exposed to periodic variations in gravitoinertial force (2-G peak) in parabolic flight maneuvers quickly come to perceive the peak force level as having decreased in intensity. By the end of a 40-parabola flight, the decrease in apparent force is approximately 40%. On successive flight days, the apparent intensity of the force loads seems to decrease as well, indicating a cumulative adaptive effect. None of the subjects reported feeling abnormally "flight" for more than a minute or two after return to 1-G background force levels. The pattern of findings suggests a context-specific adaptation to high-force levels.

Adaptation, Physiological↗
PubMed1981

Illusions of postural, visual, and aircraft motion elicited by deep knee in the increased gravitoinertial force phase of parabolic flight. Evidence for dynamic sensory-motor calibration to earth gravity force levels.

Illusions of self motion and aircraft motion are experienced when executing deep knee bends in the high force phases of parabolic flight. The occurrence of such illusions indicates that skeletomotor control is actively calibrated to a 1 g reference level and that departures from this level affect the execution and appreciation of voluntary movements. The origin of the illusory patterns is shown to be understandable in terms of "mismatches" between efferent control signals and expected patterns of associated muscle spindle activity. It is shown, too, that spindle activity is interpreted within an entire context of spatial information about ongoing and intended motion of the body and whether the body is laden.

Aerospace Medicine↗
PubMed1981

Eye-hand tracking using afterimages. Evidence that sense of effort is dependent on spatial constancy mechanisms.

Oculomotor tracking of one's unseen hand is greatly enhanced when a positive afterimage of the arm is projected onto its changing apparent position. The "afterimage arm" also influences the perception of real arm motion. The nature of this influence indicates that sense of effort or will derives from spatial computations potentially involving sensory and motor information about the ongoing orientation of the entire body.

Acoustic Stimulation↗
PubMed1981

The influence of efferent, proprioceptive, and timing factors on the accuracy of eye-hand tracking.

Oculomotor tracking of one's moving hand is considerably more accurate than tracking of an external target undergoing comparable motion. To identify the factors contributing to this enhancement of tracking accuracy, the influence of visual, proprioceptive, and efferent cues on tracking performance was assessed. Related observations were made on the influence both of linear and topological transformations between target and hand position on tracking accuracy. The experimental findings indicate that if a target light is attached to one's hand, a) the target can be tracked with comparable accuracy for active and passive limb movements, and b) when the entire hand rather than just the target light is visible, pursuit velocity is higher and more closely matches target velocity. If a linear transformation is introduced between hand and target positions, nearly identical tracking accuracy is found with voluntary and involuntary limb movements. By contrast, topological transformations degrade target tracking accuracy for passive but not for voluntary limb movements. The implications of this finding are discussed.

Adult↗
PubMed1981

Some contributions of touch, pressure and kinesthesis to human spatial orientation and oculomotor control.

Human spatial orientation and oculomotor control are under multimodal influence. It is not possible in the normal animal to stimulate differentially the vestibular receptors without activating other receptor systems whose activity may have a profound influence on postural control and experienced orientation. Many patterns of behavior and response that have been attributed solely to vestibular function are actually dependent wholly or in part on touch, kinesthetic, and proprioceptive stimulation.

Eye Movements↗
PubMed1981

Adaptation to visual displacement: contribution of proprioceptive, visual, and attentional factors.

A study is reported of the sensory and oculomotor factors that influence adaptation to visual displacement when only sight of the hand and of a target light is permitted. Ten subjects each participated in five counterbalanced sessions in which the relative contributions to adaptation of limb proprioception, oculomotor pursuit, retinal image displacement, and attention were determined. Recordings of eye position were taken throughout the sessions. A discordance between the visual direction of the hand and the proprioceptively specified position of the hand was essential but not sufficient for adaptation to occur. When such a discordance was present adaptation was enhanced by improving position sense of the arm by moving it passively, maximizing accuracy of visual tracking, and focusing attention on the hand. Attentional factors played a smaller part than has been reported for exposure situations involving error feedback about limb position. Eye-movement recordings showed that tracking the passively moved hand visually was vastly superior to tracking a target light undergoing comparable motion.

Adaptation, Ocular↗
PubMed1981

Variations in gravitoinertial force level affect the gain of the vestibulo-ocular reflex: implications for the etiology of space motion sickness.

Recordings of horizontal nystagmus were obtained on 16 male subjects exposed to repeated patterns of horizontal angular acceleration, constant velocity rotation, and sudden-stop deceleration in the laboratory and in the free-fall and high-force periods of parabolic flight. Nystagmus intensity was a clear function of gravitoinertial force level: slow phase velocity and beat frequency increased during exposure to high force levels and decreased in free-fall compared to values obtained at I G. These findings indicate that the gain of the vestibulo-ocular reflex decreases in free-fall. This fact likely accounts for the disorientation and dizziness sometimes experienced by astronauts when moving their heads in the early phases of orbital flight and again after splashdown. The implications of the present findings, both for the etiology and for the treatment of space motion sickness, are discussed.

Acceleration↗
PubMed1981

The guidance of saccadic eye movements to perceptually mislocalized visual an non-visual targets.

The present experiment examined whether saccadic eye movements to visual targets are dependent on the perceived directions of the targets or on their retinally specified directions. Perceptual mislocalizations of visual targets were induced by having the target light attached to a subject's stationary hand while his biceps or triceps muscle was vibrated. Such vibration leads to apparent extension or flexion of the subject's restrained forearm and perceived visual motion of the stationary target light (6-8). Subjects always made accurate saccadic eye movements to a visual target, even when the target was perceptually mislocalized by as much as 20 degrees. By contrast, when subjects made saccadic eye movements to a nonvisual target, the location of their hand in the dark, they always looked to the perceived direction of the target even though it did not necessarily correspond to the true direction. These findings indicate that a distinction is maintained between "reflexive aspects" of oculomotor control related to foveation and the computation of perceived visual direction.

Adult↗
PubMed1980

A sudden-stop vestibulovisual test for rapid assessment of motion sickness manifestations.

The test made use of a rotating chair mounted in a striped cylindrical enclosure, 4.6 m in diameter. The subject was exposed to the following motion profile: With eyes covered he was accelebrated at 15 degrees/s2 to clockwise volocity of 300 degrees/s and maintained at that velocity for 30 s. The chair was then decelerated to a stop within 1.5 s and maintained at rest for 30 s while physiological parameters and motion sickness symptoms were recorded. This procedure was repeated until a pre-selected motion sickness endpoint was reached or 20 stops had been made. If the endpoint was not reached, testing continued without the blindfold while the subject passively viewed the striped enclosure; if the endpoint was still not reached after 20 stops, the direction of rotation was reversed. The subject's score represented one-half the number of stops with eyes covered plus the number of stops with eyes open plus twice the number of stops after reversal of direction of rotation. Fourteen subjects were each assessed four times; the average interval between tests was 3 d. The first test was usually a poor indicator of alter performance. The second test provided a satisfactory ranking of susceptibility to motion sickness, and the results of the four sessions provided an indication of the rates of acquisition and decay of adaptation. Some advantages and uses of this new test are summarized.

Adult↗
PubMed1980

Evaluation of the relationship between motion sickness symptomatology and blood pressure, heart rate, and body temperature.

This study investigated the relationship between the development of symptoms of motion sickness and changes in blood pressure, heart rate, and body temperature. Twelve subjects were each evaluated four times using the vestibular-visual interaction test (4). The results were analyzed both within and across individual subjects. Neither a systematic group nor consistent individual relationship was found between the physiological parameters and the appearance of symptoms of motion sickness. These findings suggest that biofeedback control of the physiological variables studied is not likely to prevent the expression of motion sickness symptomatology.

Blood Pressure↗
PubMed1980

Visual and postural motion aftereffects following parabolic flight.

Postural and visual motion aftereffects may be experienced after exposure to alternating periods of free fall and increased gravitoinertial force in parabolic flight. In an aftereffect, the body feels as if it is again undergoing periodic changes in force level because of motion of the substrate; strong apparent postural motion is also accompanied by visual motion of the surroundings. The aftereffects are discussed according to a) their character, b) their time course, c) secondary symptoms associated with them, d) conditions favoring their occurrence, e) their relation to the inducing frequency, f) fragments of the complete pattern, g) their duration, and h) the importance of contact cues.

Cues↗
PubMed1980

Multiple sensory and motor cues enhance the accuracy of pursuit eye movements.

Oculomotor pursuit can be elicited by moving visual, tactile, proprioceptive, and occasionally auditory targets presented singly. Both the accuracy and amount of pursuit are enhanced if the position of the target is specified by cues from several sensory modalities. When the motion of the target is topologically related to movements of the subject's arm, the subjects's eyes are more closely phase-locked with the target and reversals of the eyes generally precede target reversal by 10-20 ms.

Acoustic Stimulation↗