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PubMed1976

Asymmetric tonic labyrinth reflexes and their interaction with neck reflexes in the decerebrate cat.

1. Tonic labyrinth and neck reflexes were studied separately and in combination in the decerebrate cat with C1 and C2 spinal roots cut. Reflex effects were observed as changes in length of the isotonically loaded medial head of triceps. 2. The tonic labyrinth reflexes acted asymmetrically on the medial head of triceps. Side-down rotation of the head produced shortening in medial triceps, whereas side-up rotations of the head resulted in a lengthening. 3. The tonic neck reflexes acted asymmetrically on the medial head of triceps. Side-down rotations of the neck produced a lengthening of medial triceps, whereas side-up rotations of the neck resulted in shortening. 4. Labyrinth and neck reflexes produce opposite effects on the same limb extensor muscle so that, if the neck innervation is intact, head tilting produces no change in muscle length. 5. It is suggested that the interaction between the labyrinth and neck reflexes contributes to the stability of the trunk, allowing the head to move freely on the body without affecting this stability. Labyrinth and neck reflexes need therefore to be considered together as a single system.

Animals↗

PubMed1990

Neural mechanisms underlying the clasp-knife reflex in the cat. I. Characteristics of the reflex.

1. The goal of this study was to characterize the clasp-knife reflex by the use of stretch and isometric contraction of ankle extensor and flexor muscles in decerebrated cats with bilateral dorsal hemisections of their spinal cords at segment T12. 2. Stretch of an extensor muscle evoked inhibition in both homonymous and synergistic extensor muscles. The similarities between homonymous and synergistic inhibition suggest that similar neural mechanisms were responsible. 3. Homonymous and synergistic clasp-knife inhibition showed several characteristic features: 1) inhibition was evoked only by large stretches that produced significant muscle force. Short stretches that did not produce large forces evoked only excitation; 2) the magnitude of clasp-knife inhibition increased with increasing initial motor output, as reflected in the level of rectified EMG; 3) the time course of reflex inhibition evoked by ramp-and-hold stretch was characterized by segmentation of EMG during ramp stretch, dynamic overshoot of inhibition at the end-of-ramp stretch, and slow but usually complete decay of inhibition during maintained stretch; 4) inhibition persisted beyond the termination of stretch, and 5) inhibition showed adaptation to repeated stretch. 4. Isometric contraction of the soleus or medial gastrocnemius, produced by electrical stimulation of the muscle nerve, also evoked powerful synergistic-reflex inhibition via similar mechanisms as stretch-evoked, clasp-knife inhibition. Stretch evoked a greater degree of inhibition than did contraction, indicating that receptors responsive to both stretch and contraction contribute to clasp-knife inhibition. 5. The reflex effects produced by stretching the soleus or medial gastrocnemius were not confined to the homonymous and close synergistic muscles. Extensor muscles were inhibited and flexor muscles were excited throughout the hindlimb, which paralleled the pattern of a flexion-withdrawal reflex evoked by cutaneous stimulation. 6. Stretch of a flexor muscle, the tibialis anterior, evoked the same spatial pattern and time course of reflex action as stretch of an extensor muscle--inhibition of extensor muscles and excitation of flexor muscles throughout the hindlimb, including homonymous excitation of the tibialis anterior. 7. We conclude that neither Golgi tendon organs nor secondary spindle afferents are likely to contribute significantly to clasp-knife inhibition because their responses to stretch and isometric contraction differ from the reflex actions evoked by stretch and contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗

PubMed1976

Electrically induced flexion reflex in gait training of hemiplegic patients: induction of the reflex.

Since the introduction of the concept of functional electrical stimulation, the use of multiple stimulation sites to activate several paretic muscles in a coordinated fashion during ambulation has been suggested. Rather than stimulating multiple muscles, we have applied a train of electrical pulses to a single skin area to activate several muscles simultaneously through the induction of a flexion reflex, and evaluated the effectiveness of this reflex in producing or assisting the swing phase of the gait cycle in the hemiplegic patient. Two considerations in selecting the best stimulus site were (1) the magnitude of the reflex as measured by the length of time the foot was off the floor following a stimulus and (2) the patient's tolerance to the stimulus. The magnitude of the reflex was proportional to the strength of the stimulus current in all skin areas tested; namely the sole, dorsum of the foot, and lower posterior thigh. Of the six patients tested a flexion reflex was not elicitable by sole stimulation in one and by posterior thigh stimulation in another. In every case, compared to the two other areas, stimulation of the sole was best tolerated and produced responses of equal or greater magnitude with the same intensity of current, even though larger voltages were required owing to greater tissue impedances. With a fixed frequency of 30 Hz, a pulse duration of 3 msec, and a stimulus current sufficient to produce the reflex, the duration of the reflex could be adjusted for each patient by varying the train duration from 100 to 700 msec. This technique offers a means of providing or assisting the swing phase in the gait training of the hemiplegic patient.

Aged↗

PubMed1989

Reflex changes in sympathetic activity affect the tooth tap-digastric reflex in rabbits.

We have previously shown that, in the anaesthetized rabbit, electrical stimulation of the sympathetic trunks inhibits the digastric opening reflex, as elicited by standardized tooth taps and monitored by integrated EMG. The site of action was most likely in the periodontal ligament, since the digastric reflex evoked by electrical stimulation of the inferior alveolar nerve was unaffected. In the present investigation we have studied the effects on the reflex of more naturally occurring changes in sympathetic activity, as induced by the baroreceptor reflex. The sympathetic discharge was increased by withdrawal of blood from the femoral vein, and reduced by electrical stimulation of the aortic baroreceptor nerve. Preliminary results in five rabbits showed that haemorrhage reduced the digastric reflex by more than 10% in 7 out of 13 tests (median 19%), while aortic nerve stimulation increased the reflex in 11 out of 13 tests (median 160%). It is therefore concluded that the tooth tap-digastric reflex may be affected also by more naturally occurring changes in sympathetic discharge.

Animals↗

PubMedDate not supplied

Participation of the beta-adrenergic receptor in the enteroruminal reflex and enteroenteric reflex.

In sheep with chronic fistulae of the small intestine and rumen the participation of the beta-adrenergic receptor was investigated in the enteroruminal reflex and enteroenteric reflex using the method of pharmacological analysis. The movements of the segments of the digestive tract with fistulae were recorded by the balloon method. A solution of hydrochloric acid administered into the ileum caused a reflex stimulation of its motor activity and inhibited the movements of the rumen. Intravenous administration of propranolol before instillation of the acid into the intestine abolished or reduced greatly the reflex inhibition of the movements of the rumen and in the small intestine it enhanced significantly the studied reflex reaction. Thus stimulation of the beta-adrenergic receptor plays an important role in the reflex stimulation of the motor activity of the rumen, and stimulation of the motor activity of the small intestine in the enteroenteric reflex is limited by the effects derived from this receptor.

Animals↗

PubMed1980

[Stapedius-reflex-audiometry by measuring the threshold for the re-inforcement of a pre-existing reflex (author's transl)].

The possibilities for predicting the pure tone threshold on the basis of the acoustic stapedius reflex threshold are improved by using two stimuli, e.g., white noise and pure tone, or two pure tones according to Sesterhenn and Breuninger. The principle of the monaural loudness summation with regard to the stapedius reflex was systematically examined with the aim to obtain the best suited range for clinical use with a double tone stimulus. The following procedure proved to be the most reliable one for an objective audiometry: A distinct reflex is produced by a basic pure tone of 4 kHz, 10 dB above its reflex threshold. The tone to be examined (1 kHz) was added with a delay of 0.5 s. A 1 kHz tone 28 dB below the reflex threshold (median) produced a clear re-inforcement of the basic reflex. Objective extrapolation possibilities from stapedius reflex threshold to pure tone threshold are thereby improved.

Acoustic Impedance Tests↗

PubMedDate not supplied

H-reflex recovery curve and reciprocal inhibition of H-reflex of the upper limbs in patients with spasticity secondary to stroke.

The H-reflex recovery curve of the lower limb is considered a useful test for the diagnosis of spasticity, and recently the reciprocal inhibition of the H-reflex has proven to be abnormal in patients affected with spasticity. We studied the H-reflex recovery curve and the reciprocal inhibition of the H-reflex in the upper limb of a group of 33 patients with different degrees of spasticity secondary to stroke. Results were compared with those of 25 controls. The aim of this study was to investigate if the two tests showed any direct correlation with the degree of spasticity and, furthermore, with other clinical measures that are present in patients with spasticity as part of an upper motoneuron syndrome (i.e., changes in muscle tone, reflexes, force, etc.). The results showed an abnormality of both tests in most patients (decrease of the three phases of inhibition in the reciprocal inhibition test and increase of the late facilitation part of the H-reflex recovery curve), and these abnormalities seem mostly to be related to muscle tone, most important being the degree of correlation between tone and changes in abnormality of the H-reflex recovery curve (P < 0.03).

Adult↗

PubMed1993

The recto-levator reflex: the description of a new reflex and its clinical application. Preliminary report.

This communication embodies the description of a technique of recording a new reflex which I call "recto-levator reflex". The study was performed on 32 normal volunteers. The technique comprises the introduction of a balloon connected with a catheter into the rectum. A concentric needle electrode was introduced into the levator ani. The rectal balloon was distended and the levator myoelectric activity was recorded. In 12 patients, the procedure was repeated after levator infiltration with xylocaine or saline. When the rectal balloon was inflated with air, the levator muscle contracted. Levator contraction increased with increasing rectal distension. Anesthetized muscle did not respond, while saline-infiltrated muscle responded to rectal distension. Latency of the reflex was calculated. The recto-levator reflex seems to play an important role at defecation. On rectal distension with stools, levator contraction opens the rectal neck. Changes in the latency or amplitude of the reflex would indicate a defect in the reflex pathway. The reflex may thus prove of diagnostic significance in defecation disorders.

Adult↗

PubMed2001

The blink reflex and the corneal reflex are followed by cortical activity resembling the nociceptive potentials induced by trigeminal laser stimulation in man.

Laser stimulation of the supraorbital regions evokes brain potentials (LEPs) related to trigeminal nociception. The aim of this study was to record the R2 component of the blink reflex and the corneal reflex in 20 normal subjects, comparing the scalp activity following these reflexes with the nociceptive potentials evoked by CO2 laser stimulation of supraorbital regions. Cortical and muscular reflexes evoked by stimulation of the first trigeminal branch were recorded simultaneously. The R2 component of the blink reflex and the corneal reflex were followed by two cortical peaks, which resembled morphologically N-P waves of LEPs. The two peaks demonstrated a difference in latency of approximately 40 ms, which is consistent with activation time of nociception. This finding suggests that these reflexes are induced by activation of small pain-related fibers.

Adult↗

PubMed1970

Reflex inhibition of monosynaptic reflexes by stimulation of type J pulmonary endings.

1. Monosynaptic reflexes, evoked from flexor and extensor hind limb muscle nerves in cats anaesthetized with pentobarbitone sodium, were depressed for several seconds after right intra-atrial injection of phenyl diguanide. Injection of the drug close to the aortic valves did not produce the same effect on the reflex. There was no obvious depression of polysynaptic reflexes on intra-atrial injection of phenyl diguanide.2. This depression of the monosynaptic reflex was present even after the administration of atropine, which lessened the hypotension due to phenyl diguanide. The blood gas tensions were also measured after the administration of phenyl diguanide, and were not altered to a degree where one would expect the depression to be secondary to a change in arterial gas tensions. The depression was also present in paralysed and artificially ventilated cats.3. The afferent pathway causing this depression of the monosynaptic reflex runs in the vagus nerve, as shown by experiments done before and after vagotomy. Intercollicular decerebration also abolished this inhibition of the monosynaptic reflex.4. Prior intravenous injection of strychnine (0.1 mg/kg) abolished the effect of intra-atrial administration of phenyl diguanide.5. It was concluded that stimulation of type J pulmonary endings causes a reflex inhibition of monosynaptic reflexes lasting for several seconds via regions of the brain cephalad to the intercollicular level.

Animals↗

PubMed1981

Dependence of the Achilles tendon reflex on the excitability of spinal reflex pathways.

Muscle afferent activity from the triceps surae was recorded during experimentally induced alterations in amplitude of the Achilles tendon jerk. No changes in the neural afferent response to tendon percussion or in the background level of neural activity occurred when the reflex response was altered by discomfort, distraction, changes in attention, or changes in the rate of tendon percussion. Reinforcement of the Achilles tendon jerk by forceful contraction of the forearm muscles did not alter the relationship between intensity of the tendon tap and amplitude of the evoked neural afferent volley. Nevertheless, such maneuvers lowered the reflex threshold and raised reflex sensitivity so that a smaller afferent volley was required to produce a tendon jerk, and an increase in the afferent volley produced a disproportionately greater increase in reflex electromyographic activity than would have occurred at rest. Reinforcement maneuvers potentiated the H-reflex but did not alter the electrically induced afferent volley or the background level of neural activity. It is concluded that these changes in reflex responsiveness occurred through intrinsic spinal mechanisms independent of the fusimotor system.

Achilles Tendon↗

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↗

PubMed1995

Efferent projections of the olivary pretectal nucleus in the albino rat subserving the pupillary light reflex and related reflexes. A light microscopic tracing study.

The olivary pretectal nucleus is a primary visual centre sensitive to luminance changes. It is involved in the pupillary light reflex, the consensual pupillary light reflex and related reflexes, such as the lid closure reflex whereby pupillary constriction takes place. Since the olivary pretectal nucleus is a small nucleus, previous studies using degeneration, horseradish peroxidase and radioactive amino acid tracing were limited regarding to the exclusiveness of the projections from the olivary pretectal nucleus. In the present study the position of the olivary pretectal nucleus in the rat was first localized by physiological recording of the neurons upon luminance stimulation. Subsequently, an anterograde tracer Phaseolus vulgaris leucoagglutinin was injected iontophoretically. This allows a much more precise localization of the olivary pretectal nucleus projections. Ascending and descending pathways originating from the olivary pretectal nucleus were observed. Ascending fibres project bilaterally to the intergeniculate leaflet, the ventral part of the lateral geniculate nucleus and ipsilaterally to the anterior pretectal nucleus. In addition, contralateral projections were observed to the zona incerta and the fields of Forel. Descending fibres project bilaterally to the periaqueductal gray, the nucleus of Darkschewitsch, the interstitial nucleus of Cajal, the Edinger-Westphal nucleus and the intermediate gray layer of the superior colliculus. Also a contralateral projection to the oculomotor nucleus and an ipsilateral projection to the pontine nucleus and the nucleus of the optic tract were found. Furthermore, the contralateral olivary pretectal nucleus received a small projection. Retrograde tracing experiments using two fluorescent dyes revealed that the fibres projecting to the contralateral olivary pretectal nucleus and to the contralateral interstitial nucleus of Cajal are collaterals. The projection from the olivary pretectal nucleus to the facial nucleus which has been described to receive an input in cats could not be confirmed for the rat. The fact that the Edinger-Westphal nucleus, the interstitial nucleus of Cajal and the superior colliculus receive an input from the olivary pretectal nucleus suggests that this primary visual centre is not only involved in the pupillary light reflex, but also in controlling eye and head position and saccadic eye movements. Although visual acuity largely depends on receptive field sizes of retinal ganglion cells and their central connections, the stronger sympathetic influence during the pupillary light reflex in animals with frontally placed eyes compared to animals with laterally placed eyes may also contribute to the higher visual acuity in animals with frontally placed eyes.

Afferent Pathways↗

PubMed1980

Incontinence of urine due to instability of micturition reflexes: Part I. Detrusor reflex instability.

Micturition reflex instability may result from malfunction of the detrusor reflex or instability of the pudendal nucleus which innervates the pelvic floor muscles and external sphincter. Detrusor instability is the result of sacral micturition reflex center (SMRC) hyperexcitability. This may be caused by underinhibition or overfacilitation of the SMRC, and there are both central and peripheral causes of each. Detrusor hypertrophy may invoke chronic overactivity of the detrusodetrusor facilitative reflex causing SMRC overfacilitation. Similarly, distal urethral stricture and/or chronic urethritis causing chronic overactivity of the urethrodetrusor facilitative reflex is a common cause of SMRC overfacilitation. Pathologic relaxation and weakness of the striated muscles of the pelvic floor and perineum resulting in underactivity of the perineodetrusor inhibitory reflex, is a common cause of SMRC underinhibition. In adult women these factors often coexist. Each may predispose to stress-induced detrusor instability and are often seen in association with, or are confused with, true stress incontinence. The distinguishing characteristics of detrusor hypertonicity and detrusor hyperreflexia are reviewed, and the various mechanisms of pseudostress incontinence and of urgency incontinence are discussed in detail.

Adult↗

PubMedDate not supplied

[Effect of polysynaptic flexion reflex on monosynaptic reflexes of calf muscles prior to and following intramuscular injection of ethylbenzatropine in drug-induced muscle rigidity].

In patients with drug-induced parkinsonism and in healthy subjects the effect of stimulation of low-threshold skin fibres of sural nerve producing the polysynaptic flexion reflex of the short head of the biceps femoris muscle on the monosynaptic H reflex of calf muscles was studied before and after administration of ethylbenzatropine. In healthy subjects stimulation of low-threshold skin nerve was followed by facilitation of H reflex in the time of 70 to 200 msec. from the conditioning stimulation to the test stimulation. After one single intramuscular dose of ethylbenzatropine this late facilitating effect disappeared. In patients with drug-induced parkinsonism stimulation of afferent fibres of flexion reflex failed to cause late facilitation of H reflex and one dose of ethylbenzatropine brought no changes. During systematic administration of the drug an evident tendency for facilitation of H reflex was observed, similarly as in healthy subjects. The results obtained in healthy subjects and in patients with drug-induced parkinsonism are explained as evidence of inhibitory action of noradrenaline in certain chains of spinal interneurons, since noradrenaline release in the spinal cord is determined by the striatal equilibrium between the cholinergic and dopaminergic systems. The corrective action of ethylbenzatropine would depend on its central action on certain spinal chains of interneurons determining transmission of impulses from dermal afferent nerves to alpha motoneurons.

H-Reflex↗

PubMed1975

Acoustic reflex and reflex decay. Occurrence in patients with cochlear and eighth nerve lesions.

Acoustic reflex and reflex decay tests were administered to 50 normal ears, 50 ears with hearing loss due to noise trauma, 50 ears that had Meniere disease, and 28 ears that had involvement of the eighth nerve. In one normal ear, ten noise trauma ears, 11 Meniere disease ears, and 24 eighth nerve lesion ears to reflexes or reflex decay that were suggestive or retrocochlear lesions were observed. Acoustic reflex and reflex decay results are also compared to tone decay results for these patients.

Acoustic Stimulation↗

PubMed1991

Straining puborectalis reflex: description and significance of a "new" reflex.

The present communication studies the technique and clinical significance of a new reflex, termed straining puborectalis reflex. Nineteen healthy volunteers with an average age of 38.2 years were studied, including ten males and nine females. The intravesical pressure, representative of intra-abdominal pressure, was measured by means of a balloon-tipped catheter introduced into the urinary bladder and connected to a pressure transducer. The electromyographic (EMG) activity of the puborectalis muscle was recorded using a concentric needle electrode inserted into the muscle. The EMG response of the puborectalis muscle to straining at different pressures was recorded. The response to two types of straining--sudden momentary and slow, sustained--was observed. The procedure was repeated in ten subjects after puborectalis infiltration with xylocaine or saline. Sudden straining evoked puborectalis contraction, whereas slow, sustained straining did not. Puborectalis contraction increased with the increase in straining intensity. These results were reproducible. The anesthetized puborectalis did not respond to straining, whereas the saline-infiltrated muscle did. The latency of the reflex was studied. Besides its role as a voluntary continent sphincter, the puborectalis seems to have a role also in the involuntary continence of the pelvic organs through the straining-puborectalis reflex. The muscle contracts on sudden straining, sealing the rectal and vesical necks and thereby preventing fecal or urinary leak. However, it is only on sudden straining that the puborectalis contracts. Slow, sustained straining as occurs during defecation and micturition does not evoke the reflex action. The straining puborectalis reflex is informative and may be incorporated as an investigative tool in patients with fecal and urinary control disorders.

Adult↗

PubMed1993

Non-reflex and reflex mediated ankle joint stiffness in multiple sclerosis patients with spasticity.

In this study, we have measured the passive, the intrinsic, and the reflex-mediated mechanical response to stretch of the ankle extensors and flexors in 13 spastic multiple sclerosis patients and 10 healthy control subjects. In the ankle flexors, the patients had no reflex-mediated stiffness. The passive stiffness was increased by 138% (95% confidence interval: 26-91%) and the intrinsic stiffness by 79% (41-158%) when compared with the healthy subjects. In the ankle extensors, the reflex-mediated stiffness and the intrinsic stiffness of the patients were equal to the reflex-mediated and the intrinsic stiffness in healthy subjects. The passive stiffness was increased by 152% (41-352%). We conclude that spastic muscles in multiple sclerosis patients have an increased non-reflex stiffness (passive plus intrinsic stiffness), and that the reflex-mediated stiffness in the extensors during a sustained voluntary contraction does not differ significantly from healthy subjects.

Adult↗