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At least 847 records · Page 47Linked to original sources
PubMed2004

Convergent and divergent effects of neck proprioceptive and visual motion stimulation on visual space processing in neglect.

Visual motion stimulation as well as neck muscle vibration are known to effectively modulate the subjective body orientation in spatial neglect. However, so far only motion stimulation has been demonstrated to substantially influence size and space distortion in neglect patients. The present study aimed to compare the two stimulation methods with respect to their potentially differential impact on subjective body orientation and on space and size distortion, in five neglect patients showing perceptual distortions. We found comparable beneficial effects during left motion stimulation and left neck vibration for the subjective straight ahead. Additionally, left motion stimulation significantly ameliorated the leftward overextension in size matching, line bisection and distance estimation in all five patients. In contrast, during neck vibration only two patients showed an improvement for line bisection and size estimation and none did so for distance estimation. Since these two patients differed from the others as they had either no visual field defects or a major visual field sparing, we suggest--based on recent anatomical and neuropsychological findings--that neck vibration only tends to improve pure neglect-related visuo-perceptual distortions whereas motion stimulation can additionally improve perceptual distortions in neglect associated with hemianopia.

Adult↗
PubMed2006

Perceived size and perceived distance of targets viewed from between the legs: evidence for proprioceptive theory.

We investigated, using three comparisons, perceived size and perceived distance of targets seen from between the legs. Five targets, varying from 32 to 163 cm in height, were presented at viewing distances of 2.5-45 m, and a total of 90 observers verbally judged the perceived size and perceived distance of each target. In comparison 1, 15 observers inverted their heads upside down and saw the targets between their own legs; another 15 observers viewed them while being erect on the ground. The results showed that inverting the head lowered the degree of size constancy and compressed the scale for distance. To examine whether these results were due to an inversion of retinal-image or body orientation, comparisons 2 and 3 were performed. In comparison 2, 15 observers stood upright and saw the targets with prism goggles that rotated the visual field 180 degrees , while other 15 observers stood upright, but viewed the targets with a hollow frame lacking the prisms. The results showed that, in both goggle conditions, size constancy prevailed and perceived distance was a linear function of physical distance. In comparison 3, 15 observers wore the 180 degrees rotation goggles and viewed the targets by bending their heads forwardly, and the other 15 observers viewed them while wearing hollow goggles and lying on the belly. The results showed a low degree of size constancy and compressed the scale for distance. Therefore, it is suggested that perceived size and perceived distance are affected by an inversion of body orientation, not of retinal image orientation. When path analysis and partial correlation analysis were applied to the whole data, perceived size was found to be independent of perceived distance. These results supported the direct perception model, rather than the apparent distance model.

Cues↗
PubMed1999

Motion sickness and proprioceptive aftereffects following virtual environment exposure.

To study the potential aftereffects of virtual environments (VE), tests of visually guided behavior and felt limb position (pointing with eyes open and closed) along with self-reports of motion sickness-like discomfort were administered before and after 30 min exposure of 34 subjects. When post- discomfort was compared to a pre-baseline, the participants reported more sickness afterward (p < 0.03). The change in felt limb position resulted in subjects pointing higher (p < 0.038) and slightly to the left, although the latter difference was not statistically significant (p = 0.08). When findings from a second study using a different VE system were compared, they essentially replicated the results of the first study with higher sickness afterward (p < 0.001) and post- pointing errors were also up (p < 0.001) and to the left (p < 0.001). While alternative explanations (e.g. learning, fatigue, boredom, habituation, etc.) of these outcomes cannot be ruled out, the consistency of the post- effects on felt limb position changes in the two VE implies that these recalibrations may linger once interaction with the VE has concluded, rendering users potentially physiologically maladapted for the real world when they return. This suggests there may be safety concerns following VE exposures until pre-exposure functioning has been regained. The results of this study emphasize the need for developing and using objective measures of post-VE exposure aftereffects in order to systematically determine under what conditions these effects may occur.

Adult↗
PubMed2000

Visual and proprioceptive shifts in perceived egocentric direction induced by eye-position.

The relation of three main effects of eye-position on perceived direction was investigated using a method of hand pointing in the horizontal plane: (1) Retinal eccentricity is overestimated with respect to the fovea by a constant factor of 2.6 degrees; (2) an extraretinal signal induces a shift in perceived visual direction (slope 0.12) that is opposite to the direction of eccentric gaze; and (3) the perceived position of the median plane of the head shifts toward the direction of eccentric eye-position (slope 0.23) while perceived trunk position remains unchanged.

Adult↗
PubMed1989

Ensemble proprioceptive activity in the cat step cycle: towards a representative look-up chart.

Analysis of the control of movement in tasks such as stepping is severely restricted by the lack of quantitative data on the ensemble activity of afferents in the numerous muscles involved. We have started to build up a quantitative "look-up-chart" of the ensemble afferent and efferent profiles in the cat step cycle. To this end, we have developed software which allows us to digitize afferent firing, muscle length and electromyogram (EMG) activity, and to align segments for averaging by choosing one or more reference points in the step cycle. The ensemble firing of triceps surae Ia afferents showed lower than expected mean and peak rates, whereas triceps group II and Ib afferents were more active than predicted. There were small but significant transients in Ia firing at foot-off and touch-down which could not be explained in terms of origin-to-insertion length lone. They were most likely caused by propagated mechanical transients or tendon compliance effects giving rise to small differences between the origin-to-insertion length and the intramuscular length "seen" by spindles. Net ensemble Ia rates, based on previous estimates of spindle populations, probably exceed 25 kilo-impulses/second (ki.p.s.) in some muscles. Inputs as large as this are likely to contribute significantly to reflex control.

Animals↗
PubMed1989

Significance of proprioceptive mechanisms in the regulation of stance.

Compensatory electromyographic (EMG) responses and several biomechanical parameters were studied following impulsive disturbance of the limbs during stance of human volunteers on a treadmill. Treadmill acceleration impulses were backwards or forwards directed, or their initial direction was reversed after 30 ms. Backwards directed impulses were followed by gastrocnemius, forwards directed ones by tibialis anterior EMG responses (latency 65 to 75 ms) whose durations depended on impulse duration. When the direction of the impulse was reversed, the respective antagonistic leg muscles were activated again with a delay of 68 to 75 ms after onset of stretch of these muscles. The behaviour of the EMG responses could best be correlated to the displacement at the ankle joint and may be described in terms of a stretch reflex response. The results indicate that these stretch reflex responses help control of the body's centre of gravity thereby preventing falling. Head movements induced by the impulses showed little correlation with the appearance of the EMG responses, suggesting that the vestibular system is unlikely to be directly involved in the generation of these responses. Vestibular signals may, however, significantly contribute to slow body sway stabilization.

Adult↗
PubMed2000

Differential contributions of the two hemispheres in intra-modal proprioceptive sensory matching in 7-10-year-old boys.

This study explores putative differential contributions of the two hemispheres when 7-10-year-old right-hand and left-hand preferent boys are required to carry out a 'foot-hand' target location and matching task. The task required subjects to locate a target pin with the big-toe (felt target), and match the located target position with the hand, without vision. Right-handed (n=25) and left-handed (n=22) boys were tested in a four-condition design. Two intra-hemispheric conditions (right foot locating-right hand matching, left foot locating-left hand matching), and two inter-hemispheric conditions (right foot locating-left hand matching, left foot locating-right hand matching) were used. When the criterion for handedness was writing hand only the results were found to be confounded by the large number of subjects with indeterminate handedness (isolated by use of the Edinburgh Handedness Inventory) originally assigned to the left-handed group. Reclassification of the handedness groups, on the basis of this inventory, showed the pure-left handers to be as good on those conditions mediated by the right hemisphere as pure right handers were with those conditions mediated by the left. These findings are discussed with respect to the contention that left handers are not just 'reversed' right handers.

Child↗
PubMed1999

Proximal versus distal control in proprioceptively guided movements of motor-impaired children.

Two groups of 7-year-old children diagnosed as motor-impaired (N = 6) or as controls (N = 6) were required to perform a task that involved locating targets under a table-top with one hand while attempting to match the position of the target with the other, on the table-top (intra-modal matching), always without visual control. The experimental design involved three different conditions: proximal control (P), distal control (D) or both (PD). Target distance errors were analysed in terms of absolute (AE) and variable error. When the scores for each hand were combined, the motor-impaired group showed inferior mean performance (AE scores) on all three conditions as compared with the control children and were also more variable in their behaviour. Analyses of scores achieved with the right and the left hand separately, however, demonstrated that the difference could largely be attributed to the scores obtained when matching with the right hand in conditions P and PD, and matching with the left hand in condition D. Possible explanations of these findings are discussed in the context of 'delay' (developmental lag) and/or 'deviancy' (neurological lesion/disconnection).

Child↗
PubMed1997

Influence of respiratory afferents upon the proprioceptive reflex of skeletal muscles in healthy humans.

Relationships between respiratory afferents and the motor drive to skeletal muscles are well documented in animals, but human data are scarce. Tonic vibratory response (TVR) elicited by mechanical tendon vibrations were explored in an arm (extensor digitorum, ED) and a leg (vastus lateralis, VL) muscle, in healthy subjects. Tendon vibrations were delivered during unloaded breathing and after 10 breathing cycles while the subject breathed through an inspiratory or expiratory resistive load in order to activate respiratory afferents. Inspiratory loaded breathing significantly enhanced TVR in ED and VL muscles whereas the effects of expiratory loading depended on the vibrated muscle (increased TVR in ED; decreased TVR in VL). These results suggest that inspiratory muscle afferents activated during inspiratory loading facilitate the gamma motor drive to arm and leg muscles whereas the activation of pulmonary vagal afferents during expiratory loading can exert a facilitating or suppressive influence on the gamma motor drive, depending on the limb muscle group.

Adult↗