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Results for “Kinesthesis”

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At least 541 records · Page 30Linked to original sources

PubMed1984

Effects of externally imposed elastic loads on the ability to estimate position and force.

Normal adult subjects attempted, with vision excluded, to match the position of the left index finger by pointing to it with the right one, using only flexion-extension movements at the right elbow. An elastic load applied at the right wrist was altered from trial to trial. When instructed to align the fingers, subjects were found to select the position of the right forearm by taking into account both a position signal and some measure of the force exerted by the elbow flexors. When instructed to match a target force, instead of position, the subjects were able to give greater weighting to signals of force than in the position matching task.

Adult↗

PubMed1984

The development of air-righting reflex in postnatal growing rabbits.

The investigations were carried out in 6 growing rabbits from the 5th day of life up to the 17th day in intervals of 3 days, as well as in 6 adult animals. The movements of the animals were filmed during free fall by means of a high speed camera (1000 pictures/s) in the frontal or the lateral view. The age-dependent development of head and shoulder rotation is described; the latency of this sensorimotor reaction decreases, and the head rotation velocity increases. The air-righting reflex is interpreted as a programmed command act. The postnatal changes in the timing of this reflex allow conclusions regarding the functional development of the spinal cord along the craniocaudal axis.

Aging↗

PubMed1985

Differential effects of ambivalent visual-vestibular-somatosensory stimulation on the perception of self-motion.

The direction of perceived self-motion was determined as a function of combined visual-vestibular and vestibulo-somatosensory stimulations about the earth's vertical z-axis by means of a rotary chair and drum system. The predominant influence of concurrent antagonistic vestibular stimulation on circular vection (CV) even at small accelerations has been demonstrated by several studies in the past. The results of the present paper do not confirm the generally assumed influence of the vestibular system on exocentric motion perception, but instead produce evidence of the dominance of the visual channel even at high acceleration levels. Using a joystick to indicate perceived self-motion, we found the following: Constant CV (visual stimulus velocity: 40 degrees/s) could only be cancelled by vestibular stimulations at oppositely directed mean angular accelerations of 26.9 +/- 9.1 degrees/s2. Smaller accelerations led merely to an acceleration level-related decrease in the perceived velocity of CV. Despite a clear decision with respect to the direction of the perceived motion, subjects (Ss) reported dizziness or even strong motion sickness symptoms. Similar results were obtained with vestibulo-somatosensory interactions. The results are interpreted in terms of an intensive visual support in the processing of visual-vestibular signals, particularly at cortical level, assuming a cortical velocity generator (CVG).

Adolescent↗

PubMed1986

Object-motion detection affected by concurrent self-motion perception: psychophysics of a new phenomenon.

Thresholds for object-motion detection are significantly raised when concurrent self-motion perception is induced by either vestibular, or visual, or cervico-somatosensory stimulation. Active sinusoidal horizontal head oscillations with compensatory vestibulo-ocular reflex (VOR) and foveal or eccentrical target presentation; 'passive' head movements with fixation suppression of the VOR; pure body oscillations with the head fixed in space (cervical stimulation); optokinetically induced apparent self-motion (circularvection). This new visual phenomenon of a physiological 'inhibitory interaction' between object- and self-motion perception seems to have a somatosensory motor analogue. It may reflect the disadventageous side effect due to unspecificness of an otherwise beneficial space constancy mechanism, which provides us with the image of a stable world during locomotion.

Adolescent↗

PubMed1987

Information processing in goal-directed movements.

Sensory-motor interaction in pointing at visual targets without sight of the pointing arm was evaluated in human subjects, using information theory. Equations were derived to determine transformation in channels with amplitude-continuous output signals, which overcome the problems involved in dividing the output into discrete bins. The equations were applied to calculate transinformation in our pointing experiment, and to predict transinformation under a variety of different experimental conditions. The results apply also to other systems that can be regarded as channels with similar properties.

Feedback↗

PubMed1988

Dynamic adaptation of the blind pointing characteristic to stepwise lateral tilts of body, head, and trunk.

Blind pointing (i.e. pointing to visual targets without seeing the pointing arm) was investigated in normal subjects in response to stepwise lateral tilts (20 degrees) of the body, head, and trunk. Blind pointing positions of the right index finger on the outer surface of a hemispherical screen were measured relative to the positions of visual targets that were presented along a horizontal line (+/- 30 degrees in head coordinates) on the inner screen surface, thus yielding a blind pointing characteristic (BPC). (1) BPC is highly reproducible and can be subdivided into separate branches for the ipsi- and contralateral hemifields. These branches are rotated relative to the target line by individually different BPC angles pi i and pi c. (2) pi i exhibits characteristic time courses (measured within 10 min following a stepwise tilt) for each paradigm. (3) Body tilt (left ear down) causes a step-like increase in pi i of up to 14 degrees; body tilt (right ear down) causes a step-like decrease in pi i to about zero. (4) Trunk tilt (right shoulder down) produces a gradual decrease in pi i of up to 6 degrees (average time constant tau T = 5 min); trunk tilt (left shoulder down) produces a gradual increase in pi i of up to 4 degrees. (5) Head tilt (left ear down) causes an increase in pi i of up to 9 degrees followed by a gradual decrease (average time constant tau H = 6 min); head tilt (right ear down) causes a step-like decrease in pi i with unsignificant further changes. These findings are discussed in terms of a neural sensorimotor coordinate transformation process receiving separate, dynamic otolith and neck afferent influences.

Functional Laterality↗

PubMed1988

Development of visual and tactile rod orientation in children.

Two groups of neurologically normal children (total number 64), aged from 4 to 13 years, were examined with the rod orientation test. In the second group, the line orientation test and finger tapping were also studied in addition to the rod orientation test. On the rod orientation test, the mean error rates decreased with age in both groups, and from the age of 10 the children performed as well as normal adults. In the period (ages 4-7 years) in which the greatest change in performance on the visual part of the rod orientation test had taken place (63%), a much smaller change occurred in the tapping frequency (23%). Thus the development of motor skills does not seem to be directly related to the development of spatial perception. The line orientation test did not show any developmental profile.

Adolescent↗

PubMed1990

Influence of visual blur on object-motion detection, self-motion detection and postural balance.

We have compared the influence of visual blurring (either by use of plastic foils or by plus lenses) on detection of object-motion and self-motion, and on visual control of postural balance. Three experiments were performed--in all of which object-motion and self-motion detection latencies (response times) and postural sway (sway path) increased with increasing visual blurring. We conclude that visual blurring either by foils or by glasses affects object- and self-motion perception and postural sway in a similar way.

Attention↗

PubMed1990

Impairment of auditory processing by simultaneous vestibular stimulation: psychophysical and electrophysiological data.

The aim of the experiments reported here was to demonstrate auditory-vestibular interaction both on a psychophysical and on an electrophysiological basis in humans. These results correspond to those recently obtained during simultaneous visual and vestibular stimulation and illustrate experimentally the importance of auditory information processing in spatial orientation. Time to detect the motion of a sound source is significantly increased when simultaneous vestibular stimulation is induced by passive sinusoidal head oscillations. This effect increased with the peak acceleration of the vestibular stimulus (197, 790 and 1777 degrees/s2). Vestibular influence on general auditory information processing without the quality of (object-) motion could be electrophysiologically demonstrated by means of brainstem auditory evoked potentials. The amplitude of component V generated by the inferior colliculi or by neuronal structures located slightly lower in the auditory tract was significantly reduced during concurrent vestibular stimulation. This neuronal brainstem area is a predominant location of biconvergent vestibulo-auditory neurons mediating intersensory information processing at an early neuronal level.

Adolescent↗

PubMed1990

Control of arm movements in a 2-dimensional pointing task.

The present study analyses in humans the control principles of sequential, unpracticed pointing movements in a 2-dimensional space. Our data reveal that variable pointing errors add up within such sequences. This finding supports the hypothesis that movement amplitude rather than position is the controlled variable of the investigated movements.

Attention↗

PubMed1990

Early sensory determinants of locomotor speed in adult cats: I. Visual compensation after bilabyrinthectomy in cats and kittens.

After a study of locomotion in cats deprived of their vestibular receptors early in life, the average speed of locomotion was measured in 3 adult cats, first before and then several months after bilateral labyrinthectomy, in a task involving free locomotion across platforms, rails or ladders and under normal illumination versus stroboscopic illumination or darkness. In the absence of visual cues, cats which received lesions as adults showed, on both wide and narrow supports, the same speed deficits as those of subjects which underwent lesions soon after birth. Visual cues were, however, used by some cats with early lesions to recover near normal performances on wide platforms. Evidence was found that the vestibular deficit comprised at least 3 components: a severe loss of dynamic balance occurred in all subjects with lesions and was mostly not compensated for by vision; a loss of the ability to keep to a straight course in darkness was observed on wide platforms, but vision considerably improved this function, even under stroboscopic illumination; a slight paw adjustment deficit was also observed on irregular supports, due to the fact that vision played a decreased role after the vestibular lesion. These effects point to the specificity of the vestibular control of balance, the availability of several sensorimotor strategies for orientation, and the complementarity of vestibular and visual inputs in guiding the subjects' step. We confirm here that vestibular inputs do not play a critical role during locomotor development, and stress the fact that peripheral visual cues about position or orientation (rather than motion), play a leading role in compensatory strategies.

Afferent Pathways↗

PubMed1990

Early sensory determinants of locomotor speed in adult cats: II. Effects of strobe rearing on vestibular functions.

Cats raised under stroboscopic illumination are known to exhibit oculomotor and visuomotor deficits, but little is known about their locomotor abilities. Four strobe-reared cats with intact labyrinths were tested in a locomotor test involving various walking surfaces and various illumination conditions. Apart from their general slowness under all the experimental conditions, these strobe cats showed no special deficit on narrow rails, which indicates that their dynamic balancing abilities were normal. In these subjects, the decrease in the use of kinetic visual cues was roughly compensated for by an increase in the use of position cues. When tested after chronic bilateral labyrinthectomy, the strobe-reared cats' locomotor speeds were identical to those of control labyrinthectomized cats, except on wide platforms involving orientation towards a visual goal. These results show that in the absence of motion-vision, vestibular control of dynamic balance can mature normally, but they suggest that other aspects of locomotion involving the processing of vestibular and kinesthetic inputs may be impaired.

Aging↗

PubMed1990

Unintentional modulations of human gait by optical flow.

Visual whole-field motion is known to trigger motor responses which minimize retinal slip (VOR, OKN and control of balance). In locomotion, however, the retinal slip is utilized to control the velocity and direction of displacement. The present experiment was aimed at determining how the velocity of optical flow affects the regulation of locomotion. Unintentional modulations in velocity, stride length and cadence were analyzed using a task in which artificial optical flow gave the subjects the impression they were walking at a different speed than they actually were. Slight but systematic modifications in locomotion were observed: experimental variation of the optical flow resulted in a decrease in stride length. None of the subjects were aware of this decrease, despite the fact that their muscular and articular afferences provided them with supraliminal information. Although visual flow velocity is usually a direct consequence of walking velocity, experimental modifications of visual flow were found here to cause unintentional modulations in locomotor parameters (stride length and cadence) more than in their product (velocity).

Acceleration↗

PubMed1993

Early stages of load compensation in human aimed arm movements.

We investigated the kinematics of pointing movements in human subjects while varying the weight load carried by their hand. In accordance with our previous study, we found that movement velocity decreased and duration increased with load size, while skewness of velocity profiles and final pointing position were load-independent. When the load was changed without advance information about the new load size, kinematics of the first movement deviated initially (within the first 135 ms) from those of the preceding and following movements. Two types of deviation were found. Firstly, the initial rise of movement velocity was slower, independent of the new load size; we attributed this finding to a purposeful motor strategy to "probe" the new relationship between force and acceleration, and thus to determine the new load size. Secondly, the initial portions of movement trajectories deviated downwards after a load increase and upwards after a load decrease, depending in a graded way on the change of load size; this finding probably reflects incomplete load compensation. Deviating movement kinematics were found only for the first movement after a load change. This suggests that information required for appropriate load compensation is determined during the first movement, is stored in memory, and is available for the execution of subsequent movements. No deviating kinematics were found if prior to the first response after a load change, subjects moved the hand orthogonally to the direction of pointing or suspended the load against gravity. This suggests that the stored information is not specific for movements of similar spatial characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗

PubMed1994

Amplitude reduction of H-reflex during mental movement simulation in elite athletes.

In order to investigate the changes of motoneuron excitability during mental simulation of a voluntary movement (motor imagery; MI), the soleus H-reflex and several activities of autonomic effectors were recorded simultaneously when MI of speed skate sprint was performed. The subjects were seven elite speed skate athletes ranging in age from 18 to 24 years old. They were all skilled in MI, and could imagine full vivid skating movement internally as if they were really exercising. The subjects were awake, relaxed and blindfolded. At first, rest (5 min), positive relaxation (4 min) and concentration periods (2.5 min) were set up. Then, after the previous announcement for the start, MI was initiated by the sound of a signal gun which was recorded by a tape recorder. MIs were continued for each subject from about 36 s to 38 s, and these imaging times were very close to the actual personal best records of each subject. The autonomic effectors represented by skin conductance response (SCR), heart rate (HR), and respiration rate (RSR) became remarkably active during MI in all trials. SCR was increased by 51% on the average. Furthermore, HR and RSR were increased by 57% and 76% respectively, compared with those during resting period. These changes in the autonomic effectors were all significant and were those which were activated in actual movements. The amplitudes of H-reflex were almost all constant before MI initiation. However, the reduction of the H-reflex amplitude arose just after the start and lasted to the end of MI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1996

Motion sensitive cells in the macaque superior temporal polysensory area: response discrimination between self-generated and externally generated pattern motion.

It was previously shown [17] that visual movement sensitive neurons lacking selectivity in the anterior parts of the dorsal superior temporal sulcus (STP) of monkeys exhibited selective responses to externally moved objects and failed to respond to the sight of the animal's own limb movements. This paper describes a series of experiments in which a monkey was trained to operate an apparatus that produced visual motion of a projected two-dimensional patterned stimulus. Single unit responses from STP were recorded and responses to visual motion, produced externally by the experimenter, were compared to the responses to visual motion (of the same pattern) produced by the monkey itself. The majority of the movement sensitive cells giving reliable responses to the pattern motion responded statistically more strongly to the experimenter-induced motion than to the motion induced by the monkey itself. The cell responses were observed not to be affected by the motion velocity and the monkey's motor activity (handle rotation without any visual stimulation) did not affect the cell's spontaneous activity. The results indicate that the response discrimination of STP cells between externally and self-induced stimulus motion is not based on form sensitivity. Moreover, the mechanism which produces the described response selectivity is not only limited to naturally occurring visual consequences of the monkey's own motor activity but is plastic and can extend to arbitrary associations between the monkey's movements and consequent visual motion.

Action Potentials↗

PubMed1995

Processing of visual motion direction in the fronto-parallel plane in the stationary or moving observer.

To examine the effect of concurrent self-motion on the perception of the direction of object-motion, random-dot kinematograms were employed in which the strength of the directional signal was manipulated by varying the percentage of coherently moving pixels. The subject's task was to indicate the motion direction of briefly presented displays while undergoing whole body rotations with angular accelerations of 0, 5, 15, or 45 degrees/s2. The perception of the direction of visual motion in the horizontal plane was impaired only when visual and vestibular motion directions were incongruous. The impairment increases with both increasing angular acceleration and decreasing percentage of coherently moving pixels. For object-motion in the vertical plane, an impairment was found for both congruous and incongruous combination of visual and vestibular stimulation, although not as pronounced for the latter (i.e., visual upward, vestibular downward stimulation, and vice versa). These results are discussed in terms of postnatal development and neurophysiological optimization processes resulting from intersensory 'updating' through every-day experience of object-motion during self-motion.

Acceleration↗

PubMed1996

Prehension with trunk assisted reaching.

For prehensile tasks, where objects are located beyond the normal reaching space, the trunk is bent forward to assist in the transport of the wrist to the object. Such task behaviors raise complex motor control issues such as how is the trunk movement incorporated into the motor plan. In this experiment, seated subjects were asked to reach and grasp a small and a large object placed on a table located beyond their maximal reach. Forward trunk bending was required to extend the reach distance. For such reaching movements, the wrist velocity consisted of a bell shape profile similar to those seen when the arm is the sole transport agent. In most trials, the trunk was the first to initiate movement, although there was no strict pattern of initiation order. The transport data showed that trunk and arm movement components were decoupled at the end of the reach. While the object was being grasped and lifted, the trunk continued moving for approximately 180 ms after the grasp. Wrist deceleration time expressed in absolute and relative values was sensitive to object size. The time from maximum peak aperture to the end of wrist movement also was significantly longer for grasping the small compared to the large object. No such relationships were observed for the trunk. Temporal coupling was only observed between the grip and wrist transport component. Time to maximum aperture was significantly correlated with time to peak wrist deceleration and only rarely with time to trunk deceleration peak. When the trunk participates in the transport of the wrist to an object, these findings suggest that only the wrist component is directly related to the achievement of the grasp. While the trunk assisted the arm to reach the object, the kinematic parameter recorded did not reveal any evidence of direct coupling. The presented data suggests that the planning takes place at the level of the hand and that endpoint is the primary variable controlled.

Acceleration↗