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Biomedical subjects

M F Reschke

Publications and source records attributed to M F Reschke.

46 records · Page 3Linked to original sources
PubMed1977

Electrodermal response in the squirrel monkey.

An effort to find evidence of electrodermal response in the squirrel monkey (Saimiri sciureus), as found in man, some infra-human genera of Simiae, and some lower mammals and amphibians, failed to locate an example. Given anatomical considerations, the availability of this response in Saimiri was suspected. In this study, using the skin conductance (constant voltage) method, monophasic electrodermal response as a result of novel or startle stimuli presentation was detected and a range of skin conductance level for test cases was determined.

Animals↗
PubMedDate not supplied

Spatial orientation during locomotion [correction of locomation] following space flight.

To investigate changes in spatial orientation ability and walking performance following space flight, 7 astronaut subjects were asked pre- and post-flight to perform a goal directed locomotion paradigm which consisted of walking a triangular path with and without vision. This new paradigm, involving inputs from different sensory systems, allows quantification of several critical parameters, like orientation performance, walking velocities and postural stability, in a natural walking task. The paper presented here mainly focuses on spatial orientation performance quantified by the errors in walking the previously seen path without vision. Errors in length and reaching the corners did not change significantly from pre- to post-flight, while absolute angular errors slightly increased post-flight. The significant decrease in walking velocity and a change in head-trunk coordination while walking around the corners of the path observed post-flight may suggest that during re-adaptation to gravity the mechanisms which are necessary to perform the task have to be re-accomplished.

Electronic Data Processing↗
PubMedDate not supplied

Directional conflict between vestibular and visual inputs in the squirrel monkey.

The directional conflict between vestibular and visual stimuli was studied in the squirrel monkey. Sinusoidal rotation was given to the subject and the direction of his visual target movement was reversed by installing a mirror in a 45 degree plane in front of the eyes. A large interindividual variance was noticed in controlling vestibular-visual conflict. The degree of vestibular-visual conflict and stimulus magnitude had no linear relationship. Also no relationship existed between vestibular-visual conflict and the provocation of vestibular nystagmus. Under the situation of vestibular-visual conflict, visual target pursuit failed to improve when two daily trials were given twice a week, for five weeks. The reduction of vestibular input created by surgery resulted in the reduction of vestibular evoked nystagmus and vestibular-visual conflict. However, their degrees were not necessarily parallel. Inter-individual difference in response of vestibular-visual conflict was related to vestibular-visual coordination.

Animals↗
PubMedDate not supplied

Further study of physical exercise and locomotor balance compensation after unilateral labyrinthectomy in squirrel monkeys.

The effect of physical exercise on compensation for locomotor asymmetry after unilateral labyrinthectomy was studied in squirrel monkeys. Five monkeys were assigned to the motor-driven rotating cage exercise, and another five, non-exercise control. Daily exercise (cumulative time of 2 1/2 hours) was given for three weeks preoperatively and continuously (daily) post-operatively. The average number of calendar days to attain the locomotor balance compensation was 20 days in the exercise group, and 35 days in the non-exercise control group. Statistical analysis showed the former compensated (according to the previously established criterion) significantly faster than the latter ( less than 0.05). Furthermore, faster reduction of gait deviation was found in the exercise group. Therefore, when physical exercise was given extensively and continuously, and locomotor balance function was measured by the squirrel monkey platform runway test (Igarashi, 1974), physical exercise application enhanced the locomotor equilibrium compensation.

Animals↗
PubMedDate not supplied

Vestibular-visual conflict sickness in the squirrel monkey.

When combined vestibular and visual (optokinetic) stimuli were given to squirrel monkeys in a direction and phase mismatching sinusoidal mode (in yaw plane), five of six monkeys exhibited actual emesis during three repeated exposures on separate trial days. Two animals vomited on two trial days and three animals, on one day. The incidence took place in 38.9% of the total trial days. When the identical vestibular and visual stimuli were given individually, the effect was negligible, thus confirming each stimulus magnitude was not stressful enough to produce emesis when used separately.

Animals↗
PubMedDate not supplied

Geometric adjustments to account for eye eccentricity in processing horizontal and vertical eye and head movement data.

Neglecting the eccentric position of the eyes in the head can lead to erroneous interpretation of ocular motor data, particularly for near targets. We discuss the geometric effects that eye eccentricity has on the processing of target-directed eye and head movement data, and we highlight two approaches to processing and interpreting such data. The first approach involves determining the true position of the target with respect to the location of the eyes in space for evaluating the efficacy of gaze, and it allows calculation of retinal error directly from measured eye, head, and target data. The second approach effectively eliminates eye eccentricity effects by adjusting measured eye movement data to yield equivalent responses relative to a specified reference location (such as the center of head rotation). This latter technique can be used to standardize measured eye movement signals, enabling waveforms collected under different experimental conditions to be directly compared, both with the measured target signals and with each other. Mathematical relationships describing these approaches are presented for horizontal and vertical rotations, for both tangential and circumferential display screens, and efforts are made to describe the sensitivity of parameter variations on the calculated results.

Eye Movements↗
PubMedDate not supplied

Postural equilibrium following exposure to weightless space flight.

Postural equilibrium performance by the Skylab 1/2, 3, and 4 crewmen following exposure to weightlessness of 28, 59, and 84 days respectively was evaluated using a modified version of a quantitative ataxia test developed by Graybiel and Fregly. Performance for this test was measured under two sets of conditions. In the first, the crewman was required to maintain postural equilibrium on narrow metal rails (or floor) with his eyes open. In the second condition, he attempted to balance with his eyes closed. A comparison of the preflight and postflight data indicated moderate postflight decrements in postural equilibrium in three of the crewmen during the eyes open test condition. However, in the eyes closed condition, a considerable decrease in ability to maintain balance on the rails was observed postflight for all crewmen tested. The magnitude of the change was most pronounced during the first postflight test day. Improvement was slow; however, on the basis of data obtained, recovery of preflight baseline levels of performance was evidently complete at the end of approximately two weeks for all crewmen. The findings are explained in terms of functional alterations in the kinesthetic, touch, vestibular and neuromuscular sensory mechanisms induced by the prolonged absence of a normal 1-G gravitational environment.

Gravitation↗
PubMedDate not supplied

Locomotor head-trunk coordination strategies following space flight.

During locomotion, angular head movements act in a compensatory fashion to oppose the vertical trunk translation that occurs during each step in the gait cycle. This coordinated strategy between head and trunk motion serves to aid gaze stabilization and perhaps simplifies the sensory coordinate transformation between the head and trunk, allowing efficient descending motor control during locomotion. Following space flight, astronauts often experience oscillopsia during locomotion in addition to postural and gait instabilities, suggesting a possible breakdown in head-trunk coordination. The goal of the present investigation was to determine if exposure to the microgravity environment of space flight induces alteration in head-trunk coordination during locomotion. Astronaut subjects were asked to walk (6.4 km/h, 20 s trials) on a motorized treadmill while visually fixating on a centrally located earthfixed target positioned either 2 m (FAR) or 30 cm (NEAR) from the eyes. In addition, some trials were also performed during periodic visual occlusion. Head and trunk kinematics during locomotion were determined with the aid of a video-based motion analyzing system. We report data collected preflight (10 days prior to launch) and postflight (2 to 4 hours after landing). The coherence between pitch head and vertical trunk movements during gaze fixation of both FAR and NEAR targets was significantly reduced following space flight indicating decreased coordination between the head and trunk during postflight locomotion. Astronauts flying on their first mission showed greater alterations in the frequency spectra of pitch head movements as compared to their more experienced counterparts. These modifications in the efficacy of head movement control may account for the reported disruption in gaze performance during locomotion and may contribute to postflight postural and gait dysfunction.

Adult↗
PubMedDate not supplied

Microgravity vestibular investigations: perception of self-orientation and self-motion.

Four astronauts experienced passive whole-body rotation in a number of test sessions during a 7-day orbital mission. Pitch (Y-axis) and roll (X-axis) rotation required subject orientations on the rotator in which the otolith system was at radius of 0.5 m. Thus subjects experienced a constant -0.22 Gz stimulus to the otoliths during the 60 s constant-velocity segments of "pitch" and "roll" ramp profiles. The Gz stimulus, a radius-dependent vector ranging from -0.22 Gz at the otoliths to +0.36 Gz at the feet, generated sensory information that was not interpreted as inversion in any of the 16 tests carried out in flight (12 in pitch and 4 in roll orientation). None of the subjects was rotated with head off-center during the first 33 h of the mission. In the state of orbital adaptation of these subjects, a -0.22 Gz otolith stimulus did not provide a vertical reference in the presence of a gradient of +Gz stimuli to the trunk and legs.

Astronauts↗