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At least 19 recordsLinked to original sources
PubMed1998

Gravitoinertial force background level affects adaptation to coriolis force perturbations of reaching movements.

We evaluated the combined effects on reaching movements of the transient, movement-dependent Coriolis forces and the static centrifugal forces generated in a rotating environment. Specifically, we assessed the effects of comparable Coriolis force perturbations in different static force backgrounds. Two groups of subjects made reaching movements toward a just-extinguished visual target before rotation began, during 10 rpm counterclockwise rotation, and after rotation ceased. One group was seated on the axis of rotation, the other 2.23 m away. The resultant of gravity and centrifugal force on the hand was 1.0 g for the on-center group during 10 rpm rotation, and 1.031 g for the off-center group because of the 0.25 g centrifugal force present. For both groups, rightward Coriolis forces, approximately 0.2 g peak, were generated during voluntary arm movements. The endpoints and paths of the initial per-rotation movements were deviated rightward for both groups by comparable amounts. Within 10 subsequent reaches, the on-center group regained baseline accuracy and straight-line paths; however, even after 40 movements the off-center group had not resumed baseline endpoint accuracy. Mirror-image aftereffects occurred when rotation stopped. These findings demonstrate that manual control is disrupted by transient Coriolis force perturbations and that adaptation can occur even in the absence of visual feedback. An increase, even a small one, in background force level above normal gravity does not affect the size of the reaching errors induced by Coriolis forces nor does it affect the rate of reacquiring straight reaching paths; however, it does hinder restoration of reaching accuracy.

Adaptation, Physiological↗
PubMed1994

Rapid adaptation to Coriolis force perturbations of arm trajectory.

1. Forward reaching movements made during body rotation generate tangential Coriolis forces that are proportional to the cross product of the angular velocity of rotation and the linear velocity of the arm. Coriolis forces are inertial forces that do not involve mechanical contact. Virtually no constant centrifugal forces will be present in the background when motion of the arm generates transient Coriolis forces if the radius of body rotation is small. 2. We measured the trajectories of arm movements made in darkness to a visual target that was extinguished as movement began. The reaching movements were made prerotation, during rotation at 10 rpm in a fully enclosed rotating room, and postrotation. During testing the subject was seated at the center of the room and pointed radially. Neither visual nor tactile feedback about movement accuracy was present. 3. In experiment 1, subjects reached at a fast or slow rate and their hands made contact with a horizontal surface at the end of the reach. Their initial perrotary movements were highly significantly deviated relative to prerotation in both trajectories and end-points in the direction of the transient Coriolis forces that had been generated during the reaches. Despite the absence of visual and tactile feedback about reaching accuracy, all subjects rapidly regained straight movement trajectories and accurate endpoints. Postrotation, transient errors of opposite sign were present for both trajectories and endpoints. 4. In a second experiment the conditions were identical except that subjects pointed just above the location of the extinguished target so that no surface contact was involved. All subjects showed significant initial perrotation deviations of trajectories and endpoints in the direction of the transient Coriolis forces. With repeated reaches the trajectories, as viewed from above, again became straight, but there was only partial restoration of endpoint accuracy, so that subjects reached in a straight line to the wrong place. Aftereffects of opposite sign were transiently present in the postrotary movements. 5. These observations fail to support current equilibrium point models, both alpha and lambda, of movement control. Such theories would not predict endpoint errors under our experimental conditions, in which the Coriolis force is absent at the beginning and end of a movement. Our results indicate that detailed aspects of movement trajectory are being continuously monitored on the basis of proprioceptive feedback in relation to motor commands. Adaptive compensations can be initiated after one perturbation despite the absence of either visual or tactile feedback about movement trajectory and endpoint error. Moreover, movement trajectory and end-point can be remapped independently.(ABSTRACT TRUNCATED AT 400 WORDS)

Acceleration↗
PubMed2000

Reaching during virtual rotation: context specific compensations for expected coriolis forces.

Subjects who are in an enclosed chamber rotating at constant velocity feel physically stationary but make errors when pointing to targets. Reaching paths and endpoints are deviated in the direction of the transient inertial Coriolis forces generated by their arm movements. By contrast, reaching movements made during natural, voluntary torso rotation seem to be accurate, and subjects are unaware of the Coriolis forces generated by their movements. This pattern suggests that the motor plan for reaching movements uses a representation of body motion to prepare compensations for impending self-generated accelerative loads on the arm. If so, stationary subjects who are experiencing illusory self-rotation should make reaching errors when pointing to a target. These errors should be in the direction opposite the Coriolis accelerations their arm movements would generate if they were actually rotating. To determine whether such compensations exist, we had subjects in four experiments make visually open-loop reaches to targets while they were experiencing compelling illusory self-rotation and displacement induced by rotation of a complex, natural visual scene. The paths and endpoints of their initial reaching movements were significantly displaced leftward during counterclockwise illusory rotary displacement and rightward during clockwise illusory self-displacement. Subjects reached in a curvilinear path to the wrong place. These reaching errors were opposite in direction to the Coriolis forces that would have been generated by their arm movements during actual torso rotation. The magnitude of path curvature and endpoint errors increased as the speed of illusory self-rotation increased. In successive reaches, movement paths became straighter and endpoints more accurate despite the absence of visual error feedback or tactile feedback about target location. When subjects were again presented a stationary scene, their initial reaches were indistinguishable from pre-exposure baseline, indicating a total absence of aftereffects. These experiments demonstrate that the nervous system automatically compensates in a context-specific fashion for the Coriolis forces associated with reaching movements.

Adaptation, Physiological↗
PubMed1995

Motor adaptation to Coriolis force perturbations of reaching movements: endpoint but not trajectory adaptation transfers to the nonexposed arm.

1. Reaching movements made in a rotating room generate Coriolis forces that are directly proportional to the cross product of the room's angular velocity and the arm's linear velocity. Such Coriolis forces are inertial forces not involving mechanical contact with the arm. 2. We measured the trajectories of arm movements made in darkness to a visual target that was extinguished at the onset of each reach. Prerotation subjects pointed with both the right and left arms in alternating sets of eight movements. During rotation at 10 rpm, the subjects reached only with the right arm. Postrotation, the subjects pointed with the left and right arms, starting with the left, in alternating sets of eight movements. 3. The initial perrotary reaching movements of the right arm were highly deviated both in movement path and endpoint relative to the prerotation reaches of the right arm. With additional movements, subjects rapidly regained straight movement paths and accurate endpoints despite the absence of visual or tactile feedback about reaching accuracy. The initial postrotation reaches of the left arm followed straight paths to the wrong endpoint. The initial postrotation reaches of the right arm had paths with mirror image curvature to the initial perrotation reaches of the right arm but went to the correct endpoint. 4. These observations are inconsistent with current equilibrium point models of movement control. Such theories predict accurate reaches under our experimental conditions. Our observations further show independent implementation of movement and posture, as evidenced by transfer of endpoint adaptation to the nonexposed arm without transfer of path adaptation. Endpoint control may occur at a relatively central stage that represents general constraints such as gravitoinertial force background or egocentric direction relative to both arms, and control of path may occur at a more peripheral stage that represents moments of inertia and muscle dynamics unique to each limb. 5. Endpoint and path adaptation occur despite the absence both of mechanical contact cues about the perturbing force and visual or tactile cues about movement accuracy. These findings point to the importance of muscle spindle signals, monitoring of motor commands, and possibly joint and tendon receptors in a detailed trajectory monitoring process. Muscle spindle primary and secondary afferent signals may differentially influence adaptation of movement shape and endpoint, respectively.

Adaptation, Physiological↗
PubMed2000

Congenitally blind individuals rapidly adapt to coriolis force perturbations of their reaching movements.

Reaching movements made to visual targets in a rotating room are initially deviated in path and endpoint in the direction of transient Coriolis forces generated by the motion of the arm relative to the rotating environment. With additional reaches, movements become progressively straighter and more accurate. Such adaptation can occur even in the absence of visual feedback about movement progression or terminus. Here we examined whether congenitally blind and sighted subjects without visual feedback would demonstrate adaptation to Coriolis forces when they pointed to a haptically specified target location. Subjects were tested pre-, per-, and postrotation at 10 rpm counterclockwise. Reaching to straight ahead targets prerotation, both groups exhibited slightly curved paths. Per-rotation, both groups showed large initial deviations of movement path and curvature but within 12 reaches on average had returned to prerotation curvature levels and endpoints. Postrotation, both groups showed mirror image patterns of curvature and endpoint to the per-rotation pattern. The groups did not differ significantly on any of the performance measures. These results provide compelling evidence that motor adaptation to Coriolis perturbations can be achieved on the basis of proprioceptive, somatosensory, and motor information in the complete absence of visual experience.

Adaptation, Physiological↗
PubMed1993

An assessment of the deflecting effect on human movement due to the Coriolis inertial forces in a space vehicle.

Under conditions of prolonged space flight, it may be feasible to restore gravity artificially using centrifugal inertial forces in a spinning vehicle. As a result, the motion of the passengers relative to the vehicle is affected by Coriolis forces. The aim of this study is to propose a theoretical method to evaluate the extent of these effects compared to other inertial or motor forces affecting movement. We investigated typical right upper limb movement in a numerical model with a two-solid-links mechanism, including a spherical joint for the shoulder and a hinge joint for the elbow. The inertial and dimensional characteristics of this model derive from measurements and computations obtained on laboratory subjects. The same is true for the movements assigned to the model. These were inferred from actual recordings of arm movement when the subject presses a button placed in front of him with his index finger. From these relative velocities, the resulting forces and moments applied to the elbow and the shoulder were computed for a 1 rad s-1 rotational speed of transport motion, using classical kinetic relations. The result is that the Coriolis moments are of the same order of magnitude as the corresponding inertial moments and one-tenth of the value of a typical elbow flexion moment. Thus, they should cause a significant disturbance in movement.

Biomechanical Phenomena↗
PubMed1975

[Physical factors in animal experiments for testing antimasspsychotic drugs].

Lemmingson et al. have observed that the movement of masspsychotic lemmings (Lemmus lemmus) shows a distinct preference for the left direction. They suggested that this is due to the influence of the Coriolis force. According to this proposition the influence of the Coriolis force on a group of masspsychotic animals has been investigated quantitatively. The results suggest the following model: Normally the influence of the Coriolos force, which on the northern hemisphere acts to the right, is compensated by a neuromuscular feedback mechanism. The tendency towards the left under masspsychotic conditions corresponds to overcompensation. The tendency to the left should also be observed on the southern hemisphere, if the direction of this compensation is determined genetically. Therefore, the test proposed by Lemmingson et al. is not suited to distinguish between the influence of the Coriolis force and the influence of biologically active left-isomer molecules.

Animals↗
PubMed1998

Adaptation in a rotating artificial gravity environment.

The centripetal force generated by a rotating space vehicle is a potential source of artificial gravity. Minimizing the cost of such a vehicle dictates using the smallest radius and highest rotation rate possible, but head movements made at high rotation rates generate disorienting, nauseogenic cross-coupled semicircular canal stimulation. Early studies suggested 3 or 4 rpm as the highest rate at which humans could adapt to this vestibular stimulus. These studies neglected the concomitant Coriolis force actions on the head/neck system. We assessed non-vestibular Coriolis effects by measuring arm and leg movements made in the center of a rotating room turning at 10 rpm and found that movement endpoints and trajectories are initially deviated; however, subjects readily adapt with 10-20 additional movements, even without seeing their errors. Equilibrium point theories of motor control errantly predict that Coriolis forces will not cause movement endpoint errors so that subjects will not have to adapt their reaching movements during rotation. Adaptation of movement trajectory acquired during Coriolis force perturbations of one arm transfers to the unexposed arm but there is no intermanual transfer of endpoint adaptation indicating that neuromotor representations of movement endpoint and trajectory are separable and can adapt independently, also contradictory to equilibrium point theories. Touching a surface at the end of reaching movements is required for complete endpoint adaptation in darkness but trajectory adapts completely with or without terminal contact. We have also made the first kinematic measurements of unconstrained head movements during rotation, these movements show rapid adaptation to Coriolis force perturbations. Our results point to methods for achieving full compensation for rotation up to 10 rpm.

Adaptation, Physiological↗
PubMedDate not supplied

The role of reafference in recalibration of limb movement control and locomotion.

The reafference model has frequently been used to explain spatial constancy during eye and head movements. We have found that its basic concepts also form part of the information processing necessary for the control and recalibration of reaching movements. Reaching was studied in a novel force environment--a rotating room that creates centripetal forces of the type that could someday substitute for gravity in space flight, and Coriolis forces which are side effects of rotation. We found that inertial, noncontacting Coriolis forces deviate the path and endpoint of reaching movements, a finding that shows the inadequacy of equilibrium position models of movement control. Repeated movements in the rotating room quickly lead to normal movement patterns and to a failure to perceive the perturbing forces. The first movements made after rotation stops, without Coriolis forces present, show mirror-image deviations and evoke perception of a perturbing force even though none is present. These patterns of sensorimotor control and adaptation can largely be explained on the basis of comparisons of efference copy, reafferent muscle spindle, and cutaneous mechanoreceptor signals. We also describe experiments on human locomotion using an apparatus similar to that which Mittelstaedt used to study the optomotor response of the Eristalis fly. These results show that the reafference principle relates as well to the perception of the forces acting on and exerted by the body during voluntary locomotion.

Arm↗
PubMed2000

Aspects of body self-calibration.

The representation of body orientation and configuration is dependent on multiple sources of afferent and efferent information about ongoing and intended patterns of movement and posture. Under normal terrestrial conditions, we feel virtually weightless and we do not perceive the actual forces associated with movement and support of our body. It is during exposure to unusual forces and patterns of sensory feedback during locomotion that computations and mechanisms underlying the ongoing calibration of our body dimensions and movements are revealed. This review discusses the normal mechanisms of our position sense and calibration of our kinaesthetic, visual and auditory sensory systems, and then explores the adaptations that take place to transient Coriolis forces generated during passive body rotation. The latter are very rapid adaptations that allow body movements to become accurate again, even in the absence of visual feedback. Muscle spindle activity interpreted in relation to motor commands and internally modeled reafference is an important component in permitting this adaptation. During voluntary rotary movements of the body, the central nervous system automatically compensates for the Coriolis forces generated by limb movements. This allows accurate control to be maintained without our perceiving the forces generated.

Adaptation, Physiological↗
PubMed1998

Toroidal coil counter-current chromatography study of the mass transfer rate of proteins in aqueous-aqueous polymer phase system.

The cause of excessive band broadening of protein samples in polymer phase partitioning by counter-current chromatography (CCC) was investigated. A simple rotary device was constructed to measure the mass transfer rates of five samples including potassium dichromate, methylene blue, lysozyme, ovalbumin and human serum albumin. The results indicated that the mass transfer rates of these samples are closely correlated with their molecular masses: the higher the molecular mass, the lower the mass transfer rate. These findings are also consistent with the partition efficiencies of these samples in the same solvent system by CCC. The beneficial effect of the Coriolis force demonstrated in protein separations by the toroidal coil centrifuge may be reasonably explained on the basis of the mass transfer resistance of protein molecules through the interface: we speculate that when the Coriolis force acts parallel to the effective coil segment it can produce large interfacial areas by dispersing the mobile phase into the stationary phase, thus accelerating the mass transfer rate of protein samples.

Chromatography, Liquid↗
PubMed1990

Acoustic streaming in a rotating fluid.

Acoustic streaming theory is derived that is applicable to a fluid that is slow moving in a reference frame that rotates with a constant angular velocity omega. A simplified streaming equation is obtained for the special case in which the acoustic angular frequency omega is large relative to omega, and the change in fluid density due to rotation alone is negligible. For this special case it is shown that the "driving force" for the acoustic streaming is independent of omega. Thus, if no acoustic streaming is present in a fluid system that is stationary, then no steady-state acoustic streaming is predicted for a similar system that rotates with constant angular velocity. For a system in which acoustic streaming is present, the flow behavior depends on the relative magnitudes of the Coriolis forces and the viscous forces. If the Ekman number is large (that is, the viscous force dominates) then the predicted flow is identical to that which would exist in a stationary system. If, on the other hand, the Ekman number is small then the Coriolis force dominates and the component of flow in the direction of the axis of rotation can be much smaller in the rotating system than in a similar system at rest.

Acoustics↗
PubMed1994

Extremely non-orthogonal axes in a sense organ for rotation: behavioural analysis of the dipteran haltere system.

Flies acquire information about self-rotation via Coriolis forces detected by their moving halteres. Information processing in the haltere system was analysed by exploiting the method of simulating rotational stimuli by vibrating the fly's body and simultaneously observing compensatory head and wing reactions. Although the force acting on one haltere contains Coriolis terms for rotations about three orthogonal axes, the one-haltered fly has only two measuring axes which are coded in lateral force components. A fly with two halteres has two vertical measuring axes and two horizontal axes, the latter spanning an angle of about 120 degrees. Thus, three-dimensional turning information is acquired by bilateral computation in a highly non-orthogonal system. In the stimulus velocity range up to 1000 degrees/s, comparison of intact and one-haltered flies demonstrates that for the head roll reaction the inputs from both halteres are summated, whereas for the pitch reaction the summated inputs are modified by bilateral inhibition. This non-linear operation results in uniform gains and axis fidelity for all stimulus directions in the case of the head reaction. Response saturation at high velocities takes place after the bilateral summation. The functional consequences of non-orthogonality in the dipteran haltere system is apparently superior sensitivity for pitch compared to roll. Minimization of the "area of confusion", an argument for orthogonality, seems to be of minor importance. The non-orthogonality necessitates a transformation from covariant projections to contravariant motor components. In tensor theory of the vestibulo-ocular reflex of vertebrates, this is widely assumed to be a linear operation performed by a metric tensor. The fly's solution is a linear tensor operation supplemented by a non-linear bilateral inhibition for the pitch reaction.

Acceleration↗