INHIBITION OF PROPRIOCEPTIVE SPINAL REFLEXES INDUCED BY CUTANEOUS AFFERENT VOLLEYS IN UNRESTRAINED CATS.
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Cats↗
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Results for “REFLEX, PROPRIOCEPTIVE”
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[Formation of orienting and defensive conditioned reflexes to proprioceptive stimuli in rabbits in ontogenesis].
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Animals↗
Reflex behavior and programming in Parkinson's disease.
Several aspects of characteristically impaired postural adjustments indicate a defective central programming of the respective EMG patterns in PD. This may be due to deficits in the supraspinal control of spinal interneuronal circuits. This impairment obviously contributes to the difficulty of these patients in performing two motor acts simultaneously. In addition, parkinsonian patients exhibit a reduced sensitivity of polysynaptic reflexes in the leg extensor muscles which correlates with their postural instability. The activity of monosynaptic reflexes is negligible, as in healthy subjects. The impairment of proprioceptive reflex function may be partially compensated for by changes of intrinsic muscle stiffness. Discrepancies in the literature about the behavior of the polysynaptic EMG responses in parkinsonian patients may in part arise from the fact that it depends on both the particular muscle under study and the actual motor task investigated.
1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
[Reflexes of hand-mouth coordination].
The author reported the results of the observation of exteroceptive and proprioceptive reflexes representing an anatomical-functional coordination of hand and mouth. Experience has shown that the best clinical use is offered by the palmomandibular reflex which, from the standpoint of clinical usableness, is incorporated in the group of the most important reflexes in the neonatal and early infancy periods. It informs us on the development of the central nervous system and also has a certain topical-diagnostic importance.
Arousal↗
Characteristics of the output from the dentate nucleus to spinal neurons via pathways which do not involve the primary sensorimotor cortex.
Experiments were performed to determine the action of the dentate output on neurons in the spinal cord mediated by pathways which do not involve the primary sensorimotor and premotor cortices. The dentate nucleus was electrically stimulated by stereotaxically placed electrodes in Rhesus monkeys whose contralateral sensorimotor and premotor cortices were ablated. The resultant changes in excitability of lumbar alpha motorneurons activated by Ia afferents from nerves innervating femoral, hamstring, gastrocnemius-soleus and peroneal muscles were measured by intracellular recordings and by determining the percent change in the amplitude of the monosynaptic reflex recorded from ventral roots. The effect of stimulation of the dentate nucleus on proprioceptive reflexes was determined by recording the changes in postsynaptic potentials evoked by selective stimulation of Ia and Ib afferent fibers. The results demonstrated that dentate nucleus exerts a significant action on the excitability of spinal neurons via pathways which do not include the sensorimotor and premotor cortices. Whether the dentate stimulus produced an increase or decrease in the excitability of these neurons was dependent upon the site within the dentate nucleus at which the stimulus was applied, demonstrating that, in the decorticate preparation, the output from this nucleus is quite heterogeneous. In addition, stimulation of the dentate nucleus in these monkeys did not affect the Ia reflex pathway but significantly changed the amplitude of the inhibitory postsynaptic potential evoked by Ib afferents in lumbar alpha motorneurons.
Animals↗
Medullary actions of tetanus toxin. An electrophysiological study in man.
Brain-stem reflexes have been studied in four patients with generalized tetanus. Inhibitory cutaneous reflexes were abolished or severely depressed. The same held true, to a lesser degree, for excitatory cutaneous reflexes with long polysynaptic pathways. Proprioceptive reflexes behaved variably. The observations are discussed in regard to the possible sources of enhanced motoneuronal activity in tetanus. It is concluded that, besides depression of inhibitory synapses on motoneurons, interneuronal damage may contribute to the tetanus symptomatology.
Adult↗
[Proximo-distal motor coordination in the locomotive appendages of the lobster].
In the walking legs, mechanical stimulation of the single chordotonal organ (CB) elicits a reflex response in the muscles of the different joints. The result presented can explain the role of the heterosegmental proprioceptive reflexes in the patterned motor activity.
Action Potentials↗
Definition of human reflex excitability by statistical analysis of quantal EMG responses.
A precise method has been devised to estimate soleus motoneurone pool excitability by probit analysis of quantal (all-or-none) reflex EMG responses to critical electrical stimulation. The technique is shown to be sensitive to changes induced by weak excitatory or inhibitory inputs and is likely to be useful in the study of monosynaptic proprioceptive reflexes.
Adolescent↗
A test of a dual central pattern generator hypothesis for subcortical control of locomotion.
This study was designed to examine the nature of neural circuits involved in subcortical inter-limb coordination and reflex modulation mechanisms of locomotion. These circuits, called central pattern generators (CPGs), are believed to receive tonic input and generate rhythmically alternating sets of commands. Although CPGs have been theorized to exist in humans, their potential dual role in inter-limb coordination and reflex modulation is unclear. In the present study, nine participants walked on a treadmill, timing their heel-strikes to a metronome which varied the phase lag from 0.5 to 1.0 pi radians (0.1 pi intervals). A stimulus was delivered to the sural nerve and reflexes were measured in the ipsilateral and contralateral lower extremities through electromyography. The similarity between phase lag conditions for both temporal coordination (i.e., relative timing aspects between muscles and/or limbs) and reflex intensities suggested that they may be controlled by the same subcortical circuitry. Two plausible explanations exist: (1) a single CPG coordinates muscular contractions and phasically alters proprioceptive reflex modulation, as well as cutaneous input, using feed-forward control; (2) two separate circuits are strongly entrained, producing synchronous outputs for inter-limb coordination and reflex modulation. The out-of-phase task used in this study was limited in discerning such a difference, if it exists.
Adult↗
[A physiological study on instability in Parkinson's disease].
To clarify roles of impairment of proprioceptive reflexes in instability of parkinsonian gait, delta EMG/delta angle of the gastrocnemius and tibialis anterior muscles was measured during the stance phase on patients with Parkinson's disease and normal controls. This ratio decreased in the gastrocnemius muscle, while it was unchanged in the tibialis anterior muscle. delta EMG/delta angle is likely to be correlated with muscle stiffness(delta muscle force/delta muscle length) that reflects from stretch reflexes. Thus our results suggest an impairment of stretch reflexes of the extensor muscle during parkinsonian gait.
Animals↗
Effects of exercise on reflexes in paraplegic monkeys.
Eight monkeys, after complete spinal cord transection at the midthoracic level, were placed in a supine position and an exercise program was given to one hindlimb but not the other. Within 3 days, the exercised limb showed more muscle tone and more active cutaneous and proprioceptive reflexes. The difference increased progressively throughout the observation period of 11 to 36 days. These results suggest an important role of afferent influence on the recovery of spinal shock. The exercise program probably protects the neuromuscular apparatus from deterioration and thus maximize the recovery.
Animals↗
Gating of reflexes in ankle muscles during human stance and gait.
Holding the body's centre of gravity steady represents the crucial variable for the stabilization of posture in upright stance in man. Results from two experimental approaches suggest that force-dependent receptors are required, in addition to the well-known systems involved in sway stabilization, for equilibrium control. One approach concerns bilateral leg muscle activation during stance. Unilateral or bilateral leg displacements were induced while subjects stood on a treadmill with split belts. A unilateral displacement induced a bilateral EMG response. During bilateral displacements the EMG activity was linearly summed or subtracted, depending on whether the legs were displaced in the same or opposite directions. Both legs acted in a cooperative manner: each limb affected the strength of muscle activation and the time-space behaviour of the other. This interlimb coordination is suggested to be mediated by spinal interneuronal circuits, which are themselves under supraspinal (e.g., cerebellar) control. The other approach concerns the modulation of postural reflexes under stimulated "microgravity" ir. water immersion. An approximately linear relationship was found between contact forces and impulse-directed EMG response amplitudes in the leg muscles. Out of water loading of the subjects resulted in no further increase of the response amplitude. It was concluded that the function of proprioceptive reflexes involved in the stabilization of posture depends on the presence of contact forces opposing gravity. Extensor load receptors are thought to signal changes of the projection of body's centre of mass with respect to the feet. The interaction of the afferent input from these receptors with the other systems involved in postural control is not yet fully understood.
Ankle↗
Intersegmental reflex coordination by a single joint receptor organ (CB) in rock lobster walking legs.
In the decapod Crustacea, Palinurus vulgaris and Fasus lalandii, the reflex influences of one particular proprioceptor organ, the coxo-basal chordotonal organ (CB), on all the muscles operating the proximal and distal joints of the same leg, have been analysed. The distal end of CB was clamped in fine forceps mounted on a servo-controlled stretcher, and CB length changes of 2 mm were applied. Motor unit activity of the different muscles was recorded as electromyograms (EMGs). 1. Two types of proprioceptive reflex evoked by CB length changes have been investigated: (a) resistance reflexes of the two levator and two depressor muscles of the same leg segment, the coxopodite, i.e. 'intrasegmental reflexes', (b) 'intersegmental reflexes' induced in the muscles operating the proximal (T-C) joint of the same leg, and in all eight muscles of the limb segments distat to CB. 2. Both levator muscles respond reflexly to imposed CB stretch (which normally occurs with limb 'depression'), while both depressors respond during CB shortening (or passive "elevation" of the leg). 3. Intersegmentally CB stretch reflexly activates the M-C extensor muscle, and sometimes facilitates the T-C remotor and C-P bender muscles. Shortening of the single CB organ of a leg excites one or two tonic motor units of the T-C promotor and M-C flexor muscles, and also facilitates the remotor, I-M reductor, and the single stretcher-opener excitatory motoneurone. 4. Some of the muscles, particularly the M-C flexor and extensor muscles, are also influenced intersegmentally by the resting length of CB, usually but not invariably in the same direction as for the corresponding dynamic reflexes. The role of the CB chordotonal organ is discussed, with particular consideration of its intersegmental reflex influence on the posture of the entire leg, and on the more complex motor behaviour of locomotion, where it may be specially significant in coordination of the limb in lateral walking. A complex picture of both tonic and dynamic, inra- and intersegmental reflex regulation of the positions and movements of the limb segments, thus emerges.
Animals↗
Proprioceptive fields of crayfish claw motor neurons.
1. Action potentials of crayfish claw motor neurons were recorded during both imposed constant-velocity displacements and imposed alternating sequences of opening and closing step movements of the dactyl. 2. Peristimulus time (PST) histograms show that the firing probabilities of two neurons, the opener inhibitor (OI) and the slow closer excitor (CE) consistently increased during opening ramp movements and declined during closing ramp movements. Hyperpolarizing synaptic potentials were observed in both cells during closing movements. 3. The proprioceptive field organizations of OI and CE were analyzed with response planes and contour planes. Each PST histogram in a plane displays the firing probability of the neuron as a function of time following step displacements at a given position. A relatively uniform early primary response followed each successive opening step. The probability of occurrence of later activity, when present, usually became more pronounced as the joint angle increased. Often both cells were silent during closing steps; when the cells were active, their firing probabilities were highest at the more open joint angles. 4. When both OI and CE were active, their spike trains were usually temporally correlated. 5. The other claw efferents did not respond to imposed movements in a consistent manner. When CE was active it was most likely to respond to closing movements near the closed position. 6. It is concluded that OI and CE are strongly and similarly influenced by proprioceptive reflexes. The responses of the two cells to imposed dactyl movements change as a function of joint angle, time after movement, and direction of movement.
Animals↗
The acute effect of the GABA-agonist, THIP, on proprioceptive and flexor reflexes in spastic patients.
THIP (Lu 2-030) is pharmacologically a specific and potent GABA-receptor-agonist which in animal studies depresses monosynaptic and, to a smaller extent, polysynaptic spinal reflexes. 5 spastic patients were investigated by means of neurophysiological tests comparing the acute effect of a single oral dose of THIP (15-25 mg) to "the test situation without drug administration" with an interval of 2 days. The neurophysiological tests included quantitative studies of proprioceptive reflexes (T-reflex, vibratory inhibition of the T-reflex, resistance to passive movement of a spastic muscle and clonus) and of the flexor reflex (threshold and latency). The voluntary power was measured by a static technique. THIP clearly reduced the monosynaptic T-reflex and reinforced vibratory inhibition of the IA monosynaptic pathway. The flexor reflex threshold was slightly increased during THIP administration, but the changes were not significant. Flexor reflex latency, resistance to passive movement, clonus and voluntary power were unchanged.
Adult↗
Modulation of jaw reflexes induced by noxious stimulation to the muscle in anesthetized rats.
Previous studies have shown that jaw reflexes and activity patterns of the jaw muscles were modulated in the presence of jaw muscle pain. However, there is no study comparing the modulatory effects on the jaw reflexes induced by noxious stimulation to the jaw muscle. To clarify this, effects of the application of mustard oil (MO), an inflammatory irritant, into the temporalis (jaw-closing) muscle on (1) jaw-opening reflex evoked by tooth pulp stimulation (TP-evoked JOR) as a nociceptive reflex, (2) jaw-opening reflex evoked by inferior alveolar nerve stimulation as a non-nociceptive reflex and (3) jaw-closing reflex evoked by trigeminal mesencephalic nucleus stimulation as a proprioceptive reflex were investigated in anesthetized rats. The MO application induced suppression of all reflexes, and the effect on the TP-evoked JOR was more prominent than on the other reflexes. To elucidate the involvement of endogenous opioid system for the suppressive effect, a systemic administration of naloxone following the MO application was conducted. The MO-induced suppressive effect on the TP-evoked JOR was reversed by the naloxone administration. The results suggest that noxious stimulation to the jaw muscle modulate jaw reflexes particularly for the nociceptive jaw-opening reflex, and the modulatory effect includes both facilitatory and inhibitory aspects. The results also suggest that pain modulatory systems such as the endogenous opioid system play a crucial role in the suppression of the nociceptive transmissions related to nociceptive reflexes, and in some pathological states, defense reflexes may not be evoked properly.
Analysis of Variance↗
Vindesine. A clinical trial with special reference to neurological side effects.
A good tumoricidal activity of vindesine (VDS) has been reported in a variety of animal tumors and in human leukemias and lymphomas. We treated 22 patients who had received no prior chemotherapy and were suffering from a variety of malignant neoplasms with 0.5 mg/m2 to 3.0 mg/m2 VDS i. v. once or three times at weekly intervals and recorded the clinical, hematologic, and especially, neurological side effects. Clinically we observed fatigue in nine patients, paresthesias in seven, myalgias in three, vertigo and diarrhea in two, and skin pains, tinnitus, gastric pains, alopecia, and tremor in one patient each. There was no obvious dose-action relationship. Paravenous injection caused cellulitis similar to that seen with vincristine. No side effects were apparent in liver (SGPT) and renal (creatinine) function tests. Hematologically there was a clear trend toward leukopenia with higher doses of DVA and a mean increase in the thrombocyte count by 51 X 10(3)/mm3 was found (sign test: P greater than 0.05). The hemoglobin level did not change. Clinical neurological examination and monitoring by electroneurography revealed no changes in tensiometer performance, motor and sensory nerve conduction velocity, motor or sensory nerve action potential amplitudes, or H-reflex responses. There was dose-related diminution of the proprioceptive reflexes, especially in the lower extremities. Even with as little as 2.0 mg/m2 VDS i. v. at weekly intervals for 3 weeks Achilles and patellar tendon reflexes were diminished or absent in all patients.
Action Potentials↗
Interactions among an ensemble of chordotonal organ receptors and motor neurons of the crayfish claw.
1. Action potentials of crayfish propodite-dactyl (PD) chordotonal organ receptors and two claw motor neurons, the opener inhibitor (OI) and slow closer excitor CE) were simultaneously monitored during imposed step and ramp movements of the dactyl or while the dactyl was held at various positions. 2. The activities of the cells during imposed displacements were analyzed using peristimulus time histograms and response and contour planes. The proprioceptive fields (PFs) of individual receptors resemble components of the more complex motor neuron PFs. Some receptors are briefly active after each successive opening step, while others do not respond to steps near the closed position but respond as the joint angle increases, becoming active when the claw is held open. Another type of receptor responds to closing movements. 3. Interactions among the various types of receptors and the two motor neurons were detected and analyzed by various statistical methods and intracellular recording techniques. The results indicate that receptors activated during opening movements and when the dactyl is held at open positions excite OI and CE via divergent functional connections. The efficacies of the connections made by a receptor may differ. Receptors activated by closing movements produce hyperpolarizing synaptic potentials in both efferents, possible directly or via interneurons. 4. It is concluded that several types of chordotonal organ receptors form an ensemble of parallel input channels, which modulates the activities of OI and CE and contributes to the generation of the spatial-temporal nonuniformities of their proprioceptive reflex responses.
Animals↗