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At least 19 recordsLinked to original sources
PubMed2003

Proprioceptive reflexes in patients with reflex sympathetic dystrophy.

Reflex sympathetic dystrophy (RSD) is a syndrome that frequently follows an injury and is characterized by sensory, autonomic and motor features of the affected extremities. One of the more common motor features of RSD is tonic dystonia, which is caused by impairment of inhibitory interneuronal spinal circuits. In this study the circuits that modulate the gain of proprioceptive reflexes of the shoulder musculature are quantitatively assessed in 19 RSD patients, 9 of whom presented with dystonia. The proprioceptive reflexes are quantified by applying two types of force disturbances: (1) disturbances with a fixed low frequency and a variable bandwidth and (2) disturbances with a small bandwidth around a prescribed centre frequency. Compared to controls, patients have lower reflex gains for velocity feedback in response to the disturbances around a prescribed centre frequency. Additionally, patients with dystonia lack the ability to generate negative reflex gains for position feedback, for these same disturbances. Proprioceptive reflexes to the disturbances with a fixed low frequency and variable bandwidth present no difference between patients and controls. Although dystonia in the RSD patients was limited to the distal musculature, the results suggest involvement of interneuronal circuits that mediate postsynaptic inhibition of the motoneurons of the proximal musculature.

Adult↗
PubMed1979

Proprioceptive reflex connections of head musculature and the mesencephalic trigeminal nucleus in the carp.

The location of the sensory cells concerned with the proprioception of respiratory and extraocular musculature in the carp was studied by retrograde transport of horseradish peroxidase. Sensory cell labeling after intramuscular HRP injection was exclusively found in the trigeminal-facial-anterior lateral line ganglion complex. The muscles innervated by the trigeminal system are represented in the more rostral ganglion areas, the muscles innervated by the facial system in the more caudal ganglion parts. Nearly all labeled cells were situated on the ipsilateral side. Sensory cells labeled after extraocular muscle injection were also found all over the V-VII ganglion, however, to a considerable degree also on the contralateral side. All muscle injections failed to give mesencephalic trigeminal cell labeling. The resluts of intranerve HRP injections in peripheral trigeminal nerve branches strongly suggests a perioral mechanoreceptive function for the mes.V neurons. A bisynaptic proprioceptive reflex model is described for respiratory musculature consisting of a sensory cranial ganglion component connected to the descending trigeminal nucleus, which on its turn links the proprioceptive ganglion cells to the trigeminal and facial motorneurons. Monosynaptic proprioceptive reflex circuits are discussed on neurophysiological grounds.

Animals↗
PubMed1992

Postural proprioceptive reflexes in standing human subjects: bandwidth of response and transmission characteristics.

1. This study investigated the reflex control of postural sway during human bipedal stance. The experiments were designed to: (i) find evidence for the operation of 'stretch reflex' pathways during quiet stance, (ii) determine the bandwidth of the reflex response, (iii) describe the reflex transmission characteristics in standing subjects, and (iv) assess the ability of subjects to make a task-dependent change in the reflex. 2. A continuous random perturbation that did not threaten stability was applied at waist level to nine standing subjects. The effects of the perturbation on ankle torque, ankle movement and soleus electromyographic activity (EMG) were identified by cross-correlation. The bandwidth of the reflex response and the transmission characteristics of reflexes that respond to ankle movement were identified by spectral analysis. Changes in these reflex responses were investigated when subjects attempted to stand as still as possible, had their eyes closed, or balanced a load equivalent to their own body in a situation in which neither visual nor vestibular reflexes would be activated. 3. When standing, a reflex response coherent with the perturbation was seen in soleus EMG at frequencies up to 5 Hz, with maximal coherence at 1.0-2.0 Hz. Reflex gain increased with frequency, and there was a frequency-dependent phase advance of soleus EMG on ankle movement reaching 135 deg at 3 Hz. When attempting to minimize sway, subjects produced a more coherent reflex response and significantly increased reflex gain. 4. The response and transmission characteristics of the lower limb proprioceptive reflex in freely standing subjects were similar to those in subjects balancing a load at the ankle, a situation in which vestibular and visual inputs could not contribute. 5. It is concluded that reflex feedback related to ankle movement contributes significantly to maintaining stance, and that much of the reflex response originates from lower limb mechanoreceptors stimulated by ankle rotation. Although reflex gain may be relatively low during quiet stance it can be increased when necessary to maintain stability.

Adult↗
PubMed1975

Lumbomuscular proprioceptive reflexes in body equilibrium.

To evaluate the role of reflexes related to the lumbar proprioceptors in maintenance of body equilibrium, changes in equilibrium function of the eyes and body were observed after unilateral procainization of the lumbar erector muscles. Observations were made on normal subjects and vertigo cases with lumbar pain after whiplash injury using various equilibrium tests. The results obtained were as follows: (1) On unilateral procainization of the lumbar erector muscles of normal subjects, eye nystagmus and disturbances of the righting reflex developed. Simultaneously, changes in drift reactions of the lower limbs were detected by the stepping test. Namely, in many of the subjects examined the direction of stepping deviation became quite different from that before procainization, and stepping after procainization tended to show slight or moderate ataxic features, associated with a sensation of unsteadiness. (2) When procaine was injected unilaterally into tender spots in the lumbar erector muscles of traumatic vertigo cases, spontaneous eye nystagmus and disturbances of the righting reflex decreased. Simultaneously, significant changes in the drift reactions of the lower limbs were observed in many of the cases examined. Namely, the direction of deviation became the opposite of that before procainization and ataxia in walking almost disappeared with reduction in vertigo. The following conclusions were drawn from these findings: (1) The effects of procaine on equilibrium of normal subjects are in sharp contrast to its effects on equilibrium of traumatic vertigo cases. Findings in the former might be due to increased imbalance between the activities of the right and left lumbar proprioceptors, while those in the latter might be due to decreased imbalance between the two. (2) These findings support the view that from the standpoint of body equilibrium, there are two phases of the proprioceptive reflex, and that Fukuda's concept of "two phases of the labyrinthine reflex, i.e., a stage of disturbance and a stage of coordination", can be applied to interpretation of the proprioceptive reflex of lumbar origin.

Adult↗
PubMed1983

Role of proprioceptive reflexes in control of feeding muscles of Aplysia.

Stretching the muscles of the buccal mass of Aplysia evoked proprioceptive reflexes. These consisted of a direct reflex in which the stretched muscle contracted and a crossed reflex in which the contralateral homolog of the stretched muscle contracted as well. Both reflexes were accompanied by corresponding changes in neural activity in the buccal nerves. The muscle contraction and efferent neural activity were abolished by blocking synaptic transmission in the buccal ganglia. Blocking neuromuscular transmission blocked the contractions but not the stretch-induced afferent neural activity. Proprioceptive responses were obtained from isolated buccal nerve-muscle preparations. Both tonic on- and on-off responses were observed. These responses persisted after blocking synaptic transmission at the muscle, indicating that they were due to afferent fibers rather than peripheral interneurons. Proprioceptive neurons with centrally located cell bodies were found. These included previously identified neurons B4 and B5 as well as small cells. Proprioceptive neurons responded to muscle stretch with peripherally initiated axonal spikes that conducted into the central nervous system (CNS) and preceded their somatic spikes. These responses persisted after blocking synaptic transmission in the CNS. Several motor neurons were found. When intracellularly stimulated, these evoked contractions of their target muscle even after blocking synaptic transmission in the CNS. The motor neurons responded synaptically to stretching the ipsilateral muscle. Some responded to stretching of the contralateral homologous muscle as well. The motor neurons differed in their axonal projections, with some projecting only ipsilaterally, others bilaterally. The majority of motor neurons were inhibited by muscle stretch due to inhibitory monosynaptic input from the proprioceptive cells B4 and B5. The stretch reflex occurred when the motor neurons fired due to postinhibitory rebound. The synaptic organization of the reflex was considered.

Animals↗
PubMed1985

Determination of excitability in human proprioceptive reflexes: analysis and characteristics of EMG thresholds of postural muscle.

In order to derive indirect indices of reflex excitability, human soleus (Sol) H reflex and direct M response threshold intensities (HT, MT) were determined by probit analysis of quantal responses elicited in the surface electromyogram (EMG). Within sessions, HT and MT co-varied with respect to time along a logarithmic time-course, both attaining effectively stable levels after 40-60 min of recording. The pattern of this co-variation was imposed by non-reflex factors, primarily the electrode system employed. Sampling distributions of stable thresholds were positively skewed (median values: HT, 5.20 mA, MT, 6.83 mA), and concurrently determined values were strongly correlated (r = 0.965). The Sol threshold ratio (HT/MT) was largely unaffected by non-reflex factors and was therefore stable within subjects, both within sessions (with respect to time) and between sessions. This ratio was normally distributed (mean = 0.753 +/- 0.079 S.D.). Criteria of indirect indices of reflex excitability are proposed: HT satisfies the criteria applicable to a relative index. However, the characteristics of the threshold ratio permit its use as a powerful absolute index of proprioceptive reflex excitability.

Adolescent↗
PubMed1982

Localization of proprioceptive reflexes in the splenius muscle of the cat.

Activity of the cat splenius muscle was modulated by sinusoidal rotation of the head around the C1-C2 joint in decerebrate cats with labyrinth intact or with all semicircular canals plugged, or, in one intact and alert cat, by rotation of the body with the head fixed in space. EMG modulation, recorded from the areas of splenius innervated by the C1-C4 nerves, was due to the cervicocollic reflex. Modulation was not uniform, but decreased with progressively more caudal recording locations; with stimuli of small amplitude it was often possible to obtain modulation of the rostral part of the muscle only. The results demonstrate localization of proprioceptive reflexes, including the stretch reflex, within the splenius muscle.

Animals↗
PubMed1985

Reciprocal inhibition of proprioceptive reflexes in man revealed by a threshold shift technique.

Variations in soleus H-reflex threshold following single conditioning stimuli to tibialis anterior afferents were studied in man by probit analysis of quantal electromyographic responses. The H-reflex threshold was elevated in 6 out of 7 subjects (conditioning-test interval, 2 ms) when conditioning strengths were greater than about 0.70 X tibialis anterior motor threshold: the degree of elevation was exponentially related to conditioning strength. Analysis of response variability indicated that in some cases weaker conditioning was also effective. These findings are consistent with the view that reciprocal inhibition effectively modulates the threshold, rather than the amplitude, of proprioceptive reflex discharge.

Adult↗