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PubMed1997

Stability of ocular counterrolling and Listing's plane during static roll-tilts.

PURPOSE: To investigate whether habituation occurs in ocular counterrolling (OCR), how stable shifted Listing's plane is, and what effects visual stimulation and alertness exert on the OCR and on Listing's plane. METHODS: Two monkeys (Macaca fuscata) were engaged in this experiment. A dual scleral search coil method was used for recording three-dimensional eye movements. Spontaneous eye movements were recorded for 2 hours in dark and light, while each monkey was held in different static roll positions (up to +/-34 degrees) with its head fixed. Eye movements were also recorded during the monkeys' drowsy periods in the dark. RESULTS: In alert conditions, OCR gains showed some fluctuations but did not change consistently for 2 hours in seven of seven sessions in the dark and in seven of nine sessions in the light. The OCR gains in the light did not differ from those in the dark. The thickness of shifted Listing's plane during the static roll-tilt was also stable for 2 hours and was within the range of the thickness of Listing's plane in the upright position in the light. During drowsy periods, the thickness of Listing's plane increased, and the gain in OCR decreased. CONCLUSION: Ocular counterrolling shows no habituation for 2 hours of static roll-tilts in the alert monkey. In the same condition, Listing's plane consistently maintains its precision. Visual input does not affect OCR, but alertness is necessary to keep the stability of OCR and Listing's plane.

Adaptation, Ocular↗
PubMed1982

[Effect of stimulation of the head of the caudate nucleus on the activity of posture muscles during development of the instrumental avoidance reflex].

In chronic experiments on dags, instrumental avoidance reflexes associated with maintenance of a certain posture, revealed prevalence of inhibitory effect of preliminary low--frequency (2/ sec) stimulation of caudate nucleus' head in the right as well as left hemisphere on electromyographic and mechanographic components of the reflex actualizing its motor program. The most dramatic changes occurred in the posture components of the EMG which suggests the importance of the caudate nucleus' head for posture organization. The caudate nucleus' head is bilaterally involved in the pretriggering processes forerunning the instrumental reflex. At the same time, a difficulty in inhibition of resolving the instrumental task proper--avoidance of the electric current--was obvious in stimulation of the caudate nucleus' head in the system of instrumental avoidance reflexes.

Animals↗
PubMed2003

Age comparison of H-reflex modulation with the Jendrássik maneuver and postural complexity.

OBJECTIVE: The purpose of this study was to examine modulation of the soleus Hoffmann (H)-reflex in response to the Jendrássik maneuver (JM) in standing positions in young and elderly subjects. METHODS: Seventeen elderly (mean age=72.0 years) and 23 young (mean age=23.2 years) apparently healthy subjects were examined in two separate experiments. The first experiment was conducted to compare the prone and standing position. The second experiment was conducted in the standing position with isotonic glideboard back support. The isotonic glideboard back support was inclined 30 degrees. In the standing position with back support, the knee and ankle joints were set at 0 degrees of flexion. All subjects were tested with two foot-positions: (1) with no soleus contraction on the platform (simple task) and (2) with an active calf muscle group contraction (complex task). To compare the amplitude of the H-reflex in each experiment between the control trials (relaxed) and JM trials (squeezing tennis balls), the stimulus intensity of 1.1 x motor threshold of the M-response was used for each subject in all body positions. RESULTS: To ensure experimental control, subjects did not show a difference in the amplitude of the trial M-response between the control and JM trials on any of the body positions. Also, no difference was found in the mean amplitude of the M-response between two different positions in either of the two experiments. Trial M-responses were all between 13 and 17% of M-max in the quiet standing position for the young subjects, and 17 and 21% for the elderly subjects. Results demonstrated that the JM facilitated the H-reflex in both young and elderly subjects. However, differential ability to modulate motoneuron excitability evoked by H-reflex pathways was found between the two groups. Young subjects demonstrated a significant difference in the amplitude of the H-reflex between control and JM trials in each standing position (P<0.05). The elderly subjects, in contrast, demonstrated no significant difference in the amplitude of the H-reflex between control and JM trials during normal standing. When examining standing with back support, the young subjects demonstrated a significant difference in the amplitude of the H-reflex between control and JM trials during both the simple and complex tasks (P<0.05). The elderly subjects, in contrast, demonstrated a significant difference only in the simple postural task (P<0.05). CONCLUSIONS: These results provide evidence of differential human spinal reflex modulation between young and elderly subjects. Further, these results may point towards the role of presynaptic inhibition in mediating these differences, and may lead to a more complete understanding of the different postural control strategies between young and elderly subjects.

Adult↗
PubMed1988

Posture in Parkinson's disease: impairment of reflexes and programming.

The leg muscle electromyographic responses induced during stance by impulsive displacements of a treadmill belt (directed forward or backward and at different rates) were studied in a group of patients with Parkinson's disease and a group of age-matched healthy subjects. Young normal subjects were also studied both before and after intake of a dopamine antagonist (haloperidol). Compensatory gastrocnemius electromyographic responses resulting from backward-directed displacements were significantly smaller in both the patients and the young normal subjects following intake of haloperidol. The reduced sensitivity of the gastrocnemius muscle to stretch correlated with an inability to compensate for the perturbations. In the patients, the gastrocnemius response was followed by enhanced activation of the tibialis anterior muscle. This was not the case in the normal subjects after intake of dopamine antagonist and is probably not, therefore, the consequence of acute dopamine deficiency. In the patients the angular rotation at the ankle joint induced during faster backward-directed displacements was slower than that in normal subjects, despite identical amounts of gastrocnemius electromyographic activity. This supports earlier findings of changes in intrinsic muscle stiffness in Parkinson's disease. None of these differences were seen when the tibialis anterior muscle was stretched. This differential behavior of the antagonist leg muscles can best be explained by the different function fulfilled by these muscles in regulation of stance and gait.

Adult↗
PubMed2002

Vestibulo-ocular, optokinetic and postural function in humans with rheumatoid arthritis.

The present study investigated vestibulo-ocular reflex (VOR), optokinetic reflex (OKR) and postural function in patients with rheumatoid arthritis (RA). Compared with controls, no differences in gaze-holding, VOR gain or phase, OKR slow phase velocity (SPV) or quick phase amplitude, optokinetic afternystagmus SPV or duration, or latency to the illusion of circularvection, were found. RA patients did exhibit greater sway in the leftward direction (P<0.01), however, this was no greater in the conditions of the Clinical Test of Sensory Interaction and Balance that increase reliance upon vestibular information. We conclude that RA patients do not exhibit substantial deficits in visual-vestibular function.

Aged↗
PubMed1984

Preparatory process for anticipatory postural adjustments: modulation of leg muscles reflex pathways during preparation for arm movements in standing man.

We have investigated, in 6 standing subjects, the time course of amplitude changes in the short latency (40-60 ms) and long latency (60-80 ms) reflex response components of gastrocnemius medialis (GM) and soleus (S) muscles during the preparatory period (time between a warning signal and a response signal) as a function of the precued direction (pull or push) of arm movement. Subjects maintained their standing posture by visual feedback during the 1.5 s preparatory period of a reaction time task. A warning signal gave advance information concerning the voluntary response to be performed which consisted of either a pull or push movement of the right arm. The excitability of the reflex pathways was evaluated by triggering a rapid rotation of the right ankle joint (dorsiflexion) applied randomly at 100, 300 or 500 ms before the response signal for arm movement. Statistical analysis of EMG amplitude (ANOVA) showed that preparatory effects were different for the two synergistic muscles with both short (spinal) and longer latency components of GM showing generalized facilitation and of S showing generalized inhibition. In addition, the longer latency, presumably supraspinal, component of the two muscles was differentially modulated according to directional advance information, showing relative facilitation for pull as compared to push trials. These reflex response modulations were emphasized in faster reaction time (RT) performers at the end of the preparatory period. It is concluded that postural preparatory processes are reflected at the spinal level in global effects and at the supraspinal level in directionally specific effects.

Adolescent↗
PubMed1981

Delayed and enhanced long latency reflexes as the possible cause of postural tremor in late cerebellar atrophy.

The pathophysiology of postural tremor was studied in 7 patients with cortical cerebellar atrophy, and compared with the responses of 14 healthy control subjects to the same tests. Both tibial nerves were simultaneously and selectively stimulated in the fossa poplitea. EMG was recorded from agonist gastrocnemius muscles and from the antagonistic anterior tibial muscles. Displacement of the centre of foot pressure, inclination of trunk and head in the anteroposterior direction, and the ankle angle were also measured. Patients and controls both exhibit a synchronized discharge in the anterior tibial muscle (antagonist) with a latency of 120 ms to stimulus onset (tib1). Tib1 is shown to be a segmental stretch reflex elicited by the contraction of the gastrocnemius (agonist). A later, presumed long-loop response occurs after another 120 ms both in gastrocnemii and anterior tibial muscles in the normal subjects. This latency, and the amplitude of the late reflex, are increased in the patient group. The synchronization of delayed long-loop reflexes and a stretch response of the gastrocnemius in response to tib1 terminate the first cycle of the postural tremor which thereafter continues by way of the same mechanism generating a contraction of the anterior tibial muscle. Postural tremor can thus be synchronized by a single bilateral electrical stimulus and can even be elicited in incipient cases of the disease. With further progression of the cerebellar atrophy the dominant frequency of the postural tremor decreases along with an increase of long-loop latencies.

Atrophy↗
PubMedDate not supplied

Influence of stimulation of the head of the caudate nucleus on the activity of postural muscles during realization of an instrumental defensive reflex.

A model of instrumental defensive reflexes associated with the maintenance of a specific posture was used in chronic experiments with four dogs to demonstrate the preferential inhibitory influence of preliminary low-frequency stimulation (2 impulses/sec) of the head of the caudate nucleus in the right and left hemispheres on the electromyographic and mechanographic components of the instrumental defensive reflex effecting the reflex motor program. Subjected to the greatest changes were the postural components of the electromyogram, which permits the postulate as to the importance of the caudate head in the organization of posture. It was shown that the caudate head is bilaterally involved in the prerelease processes preceeding the instrumental response. At the same time, the difficulty of inhibiting the performance of the actual instrumental task - the avoidance of an electric current - was noted during stimulation of the caudate head in a system of instrumental defensive reflexes.

Animals↗
PubMed1992

The effect of posture and environmental temperature on cardiovascular reflexes in normal subjects and diabetes mellitus.

This study was undertaken to determine the effects of environmental temperature (17 degrees C or 27 degrees C) and posture on heart rate variability during forced sinus arrhythmia (deep breathing), and of environmental temperature on the heart rate and blood pressure responses to standing, and to the cold pressor test. A group of non-diabetic young subjects (23 +/- 5 years) and a group of older diabetic patients (54 +/- 15 years) were studied. At 27 degrees C, supine resting heart rate and systolic blood pressure were lower than at 17 degrees C in both diabetic and non-diabetic subjects, and heart rate variability was lower than at 17 degrees C in the non-diabetic subjects (p less than 0.01) with seven of 17 abnormal or borderline results (all seven subjects had normal values at 17 degrees C). Room temperature had no effect on supine heart rate variability in the diabetic patients. At 27 degrees C heart rate variability in the upright posture was significantly greater than supine (p less than 0.001) in the non-diabetic subjects. In the diabetic subjects, heart rate variability when standing at 17 degrees C increased such that five patients classified as abnormal when supine had normal values when upright. A similar pattern was observed at 27 degrees C, although only those with normal heart rate variability showed an increase on standing. Room temperature had no effect on the responses to the cold pressor test, or the blood pressure responses to standing, although the heart rate response was greater in both groups at 27 degrees C. This study shows that care should be taken to standardize the conditions under which heart rate variability is determined.

Adult↗
PubMed1983

Toward a methodology of the short-term effects of neurodevelopmental treatment.

Neurodevelopmental treatment (NDT) is a technique widely used by physical and occupational therapists in the treatment of neuromuscular disorders; however, quantitative evidence supporting its use has yet to be provided. Several studies have attempted to examine the effects of NDT, but because of poor research methodology, conclusions drawn to support the use of NDT are not based on reliable or well-documented evidence. The purpose of this study was to develop a reliable method of measuring short-term, objective changes in children with cerebral palsy and to measure the immediate effects of NDT and play interventions. A single subject design was replicated with four subjects receiving NDT and nonspecific play over a 5-week time period. Pre- and post-test items were designed to reflect qualitative changes in movement, postural tone, and reflex activity, and were videotaped and coded using interval and time-sampling techniques. The results of this study are equivocal; they neither validate nor invalidate NDT. This study provides a methodology for the investigation of the short-term effects of NDT.

Cerebral Palsy↗
PubMed1994

Explanation of physiological muscle tremor.

This paper attempts to explain physiological muscle tremor as a protective measure against an unusual limb posture. It emphasizes that most of the events in the stretch reflex loop give rise to feedback signals that are transmitted to a supraspinal tremor generator driver which integrates the signals, drives an appropriate spinal tremor generator and stops the events in the stretch reflex loop. The unusual posture and its attendant feedback are effectively abolished and this consequentially eliminates the physiological muscle tremor.

Extremities↗
PubMed2003

Inhibition of the human soleus Hoffman reflex during standing without descending commands.

The purpose of the present study was to ascertain the contribution of peripheral sensory inputs to posture-related Hoffman reflex (H-reflex) modulation in the human soleus muscle. The soleus H-reflexes were elicited in the sitting (SI) and passive standing (ST) conditions in patients with clinically complete spinal cord injuries (SCI) and in neurologically normal subjects. The results clearly showed suppression of the H-reflex amplitude during the ST compared with the SI condition especially in the SCI group. Considering the lack of a descending neural command in the SCI patients, our findings suggest that peripheral sensory inputs primarily contribute to the reduction of the soleus H-reflex during the upright standing posture.

Adult↗
PubMed1978

Effects of bethanechol chloride on the external urethral sphincter in spinal cord injury patients.

The neuropharmacodynamics of bethanechol chloride on the external urethral sphincter in male spinal cord injury patients with chronic lesions have been investigated. There were 90 cystosphincterometric and sphincteroperineal electromyographic studies conducted on 45 subjects in 4 different positions, showing varying urodynamic patterns. A gross postural cystophincteric discordant reflex was noted in the majority of patients with recent complete upper motor neuron bladders (less than 2 years in duration). The external sphincter tends to be coordinated in late cases of quadriplegics and in all paraplegics. With the administration of bethanechol chloride there was an increase in the striated sphincter pressure profile when the patient was in the sitting position, resulting in detrusor sphincter dyssnergia. This phenomenon seems to be dose-related. When the dose of bethanechol chloride is adjusted according to the types of vesicourethral dysfunctions or in combination with dantrolene sodium the most beneficial non-surgical rehabilitation of the urinary tract can be obtained in this particular group of patients.

Adolescent↗
PubMed1969

A theory of cerebellar cortex.

1. A detailed theory of cerebellar cortex is proposed whose consequence is that the cerebellum learns to perform motor skills. Two forms of input-output relation are described, both consistent with the cortical theory. One is suitable for learning movements (actions), and the other for learning to maintain posture and balance (maintenance reflexes).2. It is known that the cells of the inferior olive and the cerebellar Purkinje cells have a special one-to-one relationship induced by the climbing fibre input. For learning actions, it is assumed that:(a) each olivary cell responds to a cerebral instruction for an elemental movement. Any action has a defining representation in terms of elemental movements, and this representation has a neural expression as a sequence of firing patterns in the inferior olive; and(b) in the correct state of the nervous system, a Purkinje cell can initiate the elemental movement to which its corresponding olivary cell responds.3. Whenever an olivary cell fires, it sends an impulse (via the climbing fibre input) to its corresponding Purkinje cell. This Purkinje cell is also exposed (via the mossy fibre input) to information about the context in which its olivary cell fired; and it is shown how, during rehearsal of an action, each Purkinje cell can learn to recognize such contexts. Later, when the action has been learnt, occurrence of the context alone is enough to fire the Purkinje cell, which then causes the next elemental movement. The action thus progresses as it did during rehearsal.4. It is shown that an interpretation of cerebellar cortex as a structure which allows each Purkinje cell to learn a number of contexts is consistent both with the distributions of the various types of cell, and with their known excitatory or inhibitory natures. It is demonstrated that the mossy fibre-granule cell arrangement provides the required pattern discrimination capability.5. The following predictions are made.(a) The synapses from parallel fibres to Purkinje cells are facilitated by the conjunction of presynaptic and climbing fibre (or post-synaptic) activity.(b) No other cerebellar synapses are modifiable.(c) Golgi cells are driven by the greater of the inputs from their upper and lower dendritic fields.6. For learning maintenance reflexes, 2(a) and 2(b) are replaced by2'. Each olivary cell is stimulated by one or more receptors, all of whose activities are usually reduced by the results of stimulating the corresponding Purkinje cell.7. It is shown that if (2') is satisfied, the circuit receptor --> olivary cell --> Purkinje cell --> effector may be regarded as a stabilizing reflex circuit which is activated by learned mossy fibre inputs. This type of reflex has been called a learned conditional reflex, and it is shown how such reflexes can solve problems of maintaining posture and balance.8. 5(a), and either (2) or (2') are essential to the theory: 5(b) and 5(c) are not absolutely essential, and parts of the theory could survive the disproof of either.

Animals↗
PubMed1998

[What change was caused under short-time treatment by the Ueda method for severely disabled infants with cerebral palsy? Report of two cases].

A new physical therapy, Ueda method (UM), were performed on two patients with severe motor and intellectual disabilities syndrome and spastic cerebral palsy (CP). The period of the UM therapy was 5 days in one case with spastic CP and 10 days in another case with rigo-spastic CP. They showed the remarkable reduction of abnormal muscle tone and interesting phenomena such as postural changes of extremities and changes of some primitive reflexes. First, peculiar postures of treated extremities appeared on the first day of the UM therapy, associated with the reducing muscle tone of extremities only in the treated side. One case showed immediate change of the posture of treated upper extremity from internal to external rotation of the shoulder joint. Another case disclosed immediate appearance of internal rotation of the hip joint of the treated lower extremity and scissoring posture of legs. These phenomena were transient and disappeared under the UM treatment. Secondly, interesting phenomena in some primitive reflexes were observed after the beginning of the UM therapy. Moro reflex was elicited only in the treated upper extremity, which could not be obtained by stimuli before the UM therapy. After the UM therapy on bilateral arms. Moro reflex appeared bilaterally in two cases. On the other hand, the degree of asymmetrical tonic neck reflex (ATNR) in one case with spastic CP reduced on 5th days under the UM therapy. In another case with rigo-spastic CP automatic walking disappeared on 3rd days after the UM therapy and ATNR appeared. The first phenomena could be due to imbalances of the reduced muscle tones by the UM therapy. Second phenomena could result from the interaction between the nervous systems of Moro reflex, ATNR and automatic walking and the nervous system owing to the abnormal muscle hypertone. Moro reflex might be suppressed by abnormal muscle hypertone. The disappearance of some primitive reflexes might not depend on the maturation of the central nervous system.

Cerebral Palsy↗