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At least 901 records · Page 50Linked to original sources
PubMed2000

The effect of age-related declines in proprioception and total knee replacement on postural control.

BACKGROUND: An experiment was designed to examine the effects of a decrease in threshold joint position sense (TJPS) at the knee and ankle and of total knee replacement (TKR) on postural control in older adults. It was hypothesized that older adults with a decrease in TJPS and those who had undergone TKR would display increased center of pressure (COP) variance during quiet stance and late onsets for muscle responses to balance threats. METHODS: Older adult subjects (> or = 70 years) were evaluated and grouped according to the status of their ankle and knee threshold joint position sensation as well as their surgical history. COP data were collected while subjects stood on a force plate with feet together under eyes-open and -closed conditions. Threats to balance were given using a platform that moved forward and backward. RESULTS: Older subjects with poor knee extension TJPS had significantly increased COP variance, although those with very poor knee flexion and extension TJPS demonstrated even greater increases. Similarly, subjects with decreased ankle TJPS demonstrated increased COP variance. However, reduced TJPS did not affect the ability of subjects to respond to threats to balance. Post-TKR subjects showed no reductions in any aspect of postural control. CONCLUSIONS: This study showed that the task of standing quietly has a direct relationship to threshold JPS, although the task of recovering from an abrupt perturbation does not. Older adult TKR results suggest that there is no negative effect on balance from elective joint replacement.

Aged↗
PubMed1994

Differential roles with aging of visual and proprioceptive afferent information for fine motor control.

The goal of this study was to determine whether aging brings modifications to the role played by different sources of afferent information for movement control. Older and younger subjects practiced an aiming task for either 40 or 200 trials while different sources of afferent information were available. Following the practice phase, all subjects were submitted to transfer tests in which the afferent information was either maintained or modified. Results indicate that modifying the sources of afferent information available for motor control from acquisition to transfer minimal effects for the older subjects but caused large increase in error for the younger subjects. These results suggest that learning is specific to the sources of afferent information available while practicing the task for the younger subjects, whereas older subjects show more flexibility in their utilization of afferent information for motor control.

Adult↗
PubMed2006

Visual proprioception in the timing of movements: evidence from deafferentation.

The present study investigated the control of movements in two patients with severe somatosensory deafferentation by systematically manipulating the visual information about the produced movements. In a synchronization task requiring the production of finger taps in synchrony with a regular auditory signal, participants controlled their movements under full vision or when the sight of the effector was partially or completely occluded. Results demonstrated large effects of visual feedback on the synchronization performance in the deafferented patients. Although the patients' performance differed substantially from that of unimpaired controls under partial or no feedback, their performance was comparable under full vision, the latter suggesting a compensation of the somatosensory loss by visual monitoring.

Adult↗
PubMed1999

Predicting vestibular, proprioceptive, and biomechanical control strategies in normal and pathological head movements.

Little is known of the functionality of the vestibulocollic reflex (VCR) and cervico-collic reflex (CCR) during head and neck movements caused by perturbations of the trunk. Previously, we formulated mathematical expressions for these neck reflexes and incorporated them into a model of horizontal plane head movements. The formalism of this neuromechanical model allowed us to examine separately the main components of head movement control. In the present study, we examine selected parameters within the main components of the model, and associate variations of these parameters with disease processes affecting head and neck movements, such as loss of sensory input or modification in central or motor function. Our simulations led us to several conclusions. First, the probable use of the VCR and CCR in yaw plane head movements is to tune the head response. In the time domain, they diminish natural head oscillations (head wobble) related to head mechanics. Equivalently, in the frequency domain, they reduce the amplitude of head wobble (resonances) around 2 Hz. Second, our simulations suggest that the VCR is about ten times stronger than the CCR in normal humans. Moreover, this disproportion is associated with only very minor contributions from the CCR in yaw. Third, head oscillations (or instability) can be generated by mechanical or neural changes in the head and neck system. Finally, readjustments of central nervous system dynamic operations could provide mechanisms to compensate for sensory and motor dysfunction caused by disease.

Adult↗
PubMed1998

Central projection of proprioceptive information from the wrist joint via a forearm 'muscle' nerve in the cat.

1. Peripheral nerves arising in joint capsules are known to contain a 'contaminating' contribution from muscle afferent fibres. In the present report we provide the first electrophysiological evidence that some joint afferent fibres may take an 'ectopic' path to the central nervous system via a nearby muscle nerve. 2. Experiments were conducted in anaesthetized cats in which a distal extension of the indicis proprius nerve was observed to project beyond its own muscle to the dorsal surface of the wrist joint capsule which is also supplied by the 'classic' wrist joint nerve, a branch of the dorsal interosseous nerve. Both the proximal and distal segments of the indicis proprius nerve were exposed for recording, by means of silver hook electrodes, while each segment remained in continuity. 3. Individual wrist joint afferent fibres with receptive fields on the dorsal surface of the joint capsule could be identified electrophysiologically within the distal segment of the indicis proprius nerve. In each of these cases the same fibre could also be identified at the proximal recording site. The identity of each of these simultaneously recorded units was established (1) by the short fixed interval between their times of spike occurrence, (2) from the exact correspondence of the capsular receptive field for the simultaneously recorded spikes, and (3) by the unfailing correlation in the presence, or absence, of the distally and proximally recorded spikes in association with either manual or controlled stimulation of the wrist joint capsule. Most joint afferent fibres identified with this projection path were in the group II range of conduction velocities and had conventional properties but group III fibres also appeared to be represented. 4. The present demonstration that some joint afferent fibres may be located within 'muscle' nerves emphasizes the importance of activating deep inputs, of joint or muscle origin, by adequate stimulation of the peripheral receptors in order to examine selectively the central actions of either source of input. Electrical stimulation of the peripheral nerves may lead to interpretative ambiguities.

Afferent Pathways↗
PubMed1999

The interaction of otolith and proprioceptive information in the perception of verticality. The effects of labyrinthine and CNS disease.

A review of recent experiments in patients with labyrinthine and neurological disorders assessing the subjective postural vertical (SPV) and the subjective visual vertical (SVV) is presented. The SPV was measured with subjects (Ss) seated in a motorized flight simulator tilting at 1.5 deg/s in roll and pitch; the Ss' task was to indicate when they entered and left self-verticality. The SVV was measured by Ss adjusting a straight line to what they perceived as gravitational upright. Clear dissociations between the SVV and SPV were found, for example, patients with acute unilateral vestibular disorders had marked tilts of the SVV toward the side of the lesion but a "lean" (bias, tilt) of the SPV was never found. Dissociations of the SPV and SVV could also be induced in normal subjects by roll-plane visual motion stimuli: the SVV was tilted in the direction of motion, but the SPV was not. Prolonged lateral body tilt did, however, bias the SVV (the "A" effect) and the SPV, but these effects are likely to be mediated by somatosensory rather than otolithic input. Evidence for the latter came from (i) findings in patients with absent vestibular function, who showed an enhanced "A" effect, and (ii) from a patient with a thalamic infarction, who showed absence of the "A" effect when leaning on the hemihypesthetic side. In separate experiments where normal Ss indicated space-vertical and space-horizontal with saccadic eye movements, we found differences between these percepts, that is, subjective external space lost orthogonality. The findings in these various experiments can be interpreted if we abandon the idea of a single, "internal representation" of verticality. Different sensory modalities convey different and sometimes conflicting messages about verticality. Otolithic and somatosensory signals can have opposite sign effects during verticality estimates while tilted. In man, somatosensory cues have a prominent role in verticality perception.

Body Image↗
PubMed1983

The afferent volleys responsible for spinal proprioceptive reflexes in man.

1. To define the neural volleys responsible for the Achilles tendon jerk and the H reflex, muscle afferent activity was recorded using micro-electrodes inserted percutaneously into appropriate fascicles of the tibial nerve in the popliteal fossa.2. The response of soleus muscle afferents to tendon percussion consisted of a dispersed volley, starting 3.5-7.0 ms after percussion, increasing to a peak over 6.5-11.0 ms, and lasting 25-30 ms, depending on the strength of percussion. Electrical stimuli to the sciatic nerve at a level adequate to evoke an H reflex but subthreshold for the M wave produced a more synchronized volley, the fastest fibres of which had conduction velocities of 62-67 m/s, and the slowest 36-45 m/s.3. The wave of acceleration produced by percussion subthreshold for the ankle jerk spread along the skin at over 150 m/s. Midway between the bellies of the gastrocnemii it consisted of a damped oscillation with four to five separate phases and maximum amplitude approximately one-twentieth of that recorded on the Achilles tendon.4. With ten primary spindle endings, tendon percussion subthreshold for the ankle jerk elicited two to five spike discharges per tap, the shortest interspike intervals being 4-7 ms. Tendon percussion elicited single discharges from two Golgi tendon organs, and altered the discharge pattern of a single secondary spindle ending. The degree of dispersion of the multi-unit muscle afferent volley can be explained by the pattern of discharge of primary spindle endings.5. Percussion on the Achilles tendon evoked crisp afferent volleys in recordings from nerve fascicles innervating flexor hallucis longus, tibialis posterior, the intrinsic muscles of the foot and the skin of the foot. Electrical stimuli delivered to the tibial nerve in the popliteal fossa at a level sufficient for the H reflex of soleus produced either a volley in muscle afferents from the intrinsic muscles of the foot or a volley in cutaneous afferents from the foot.6. For comparable stimuli in the two positions, the H reflex was inhibited but the Achilles tendon jerk enhanced when the ankle was dorsiflexed from 105 degrees to 90 degrees .7. The duration of the rise times of the excitatory post-synaptic potentials (e.p.s.p.s) produced in soleus motoneurones by electrical stimulation, and by tendon percussion subthreshold for the H reflex and the ankle jerk respectively, was estimated from post-stimulus time histograms of the discharge of voluntarily activated single motor units in soleus. The mean e.p.s.p. rise times were 1.9 ms for electrical stimulation and 6.6 ms for tendon percussion. There was evidence that the duration of the electrically evoked e.p.s.p. was curtailed by an inhibitory post-synaptic potential (i.p.s.p.) of only slightly longer latency than the e.p.s.p.8. The mechanically induced and electrically induced afferent volleys are not homogeneous volleys in group I a afferents from triceps surae. The afferent volleys differ in so many respects that it is probably invalid to compare the H reflex and tendon jerk as a measure of fusimotor activity. It is suggested that neither reflex can be considered a purely monosynaptic reflex.

Achilles Tendon↗