Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “REFLEX”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

The Hoffmann reflex (H-reflex) in senile dementia of the Alzheimer's type--preliminary results.

The Hoffmann reflex (H-reflex) and direct motor response (M) were investigated (latency, amplitude and excitability curves were analyzed) in patients with senile dementia of the Alzheimer's type (SDAT). M responses had similar latencies in SDAT patients and old control subjects. H reflex latencies were similar in SDAT patients and old control subjects but longer than in younger controls. The H max/M max ratio was also lower in SDAT patients and old control subjects than in younger controls. The excitability curve of the H-reflex (using a double shock procedure) in SDAT patients was lower than in non-demented old controls for all values of the interstimulus intervals.

Aged↗
PubMed1976

[Descending long-loop reflexes in the human spinal cord I. Facilitation of the triceps surae H reflex following stimulation of forelimb afferences (author's transl)].

The H reflex in the triceps surae muscle was elicited by just supraliminal stimulation of the tibial nerve. It was conditioned by paired impulses to the brachial plexus or the forelimb nerves and in some cases to other sites of the body. With a conditioning test interval of 32-47 msec a facilitation occurred which reached its maximum at about 80 msec and lasted for about 400 msec. The facilitation evoked by ipsilateral conditioning had a shorter latency than that from contralateral (ipsilateral: 32-42 msec, contralateral; 37-47 msec). The facilitation at the optimum interval (about 80 msec) ranged between 1;5 and 11.3 times of the control values. Ipsilateral conditioning was slightly more effective than the contralateral one (Fig. 1, 2). Stimulation of different forelimb nerves at an interval of 80 msec showed only insignificant differences in the amount of facilitation but was more effective than skin stimulation in the most cases (Fig. 3). Varying the intensity of the conditioning stimulus showed that facilitation occurred with just perceptable stimuli but it became more pronounced as soon as pain threshold (2-3 time of perception threshold) was exceeded (Fig. 3). This suggests that facilitation was mainly due to activation of nociceptor afferents. From the onset of facilitation and the conduction velocities of the respective forelimb and hindlimb afferents (cf. 6) a central reflex lantency of about 43 msec was calculated. To get further insight into the central connections of the reflex loop the H reflex was conditioned by paravertebral stimulation at C5 and L1 level. Both stimuli caused a distinct facilitation. However, the latency of the onset was 10-15 msec shorter with lumbar stimulation than with cervical stimulation. This and the similar time course of facilitation seen in animal experiments (12) suggest that an early part of facilitation is mediated via a descending propriospinal pathway. The major part, however, is supposed to be mediated via supraspinal pathways and seems to be related to a startle response.

Animals↗
PubMed1996

Axon reflexes or ephaptic responses simulating blink reflex R1 after XII-VII nerve anastomosis.

It has been claimed that functional recovery of the blink reflex occurs after hypoglossal-facial nerve anastomosis. This has been explained through central nervous system plasticity and reorganization of neuronal connections. In 5 patients with reinnervated facial muscles after hypoglossal-facial nerve anastomosis we observed "R1-like" responses that fulfilled criteria for facial nerve axon reflexes or ephapses. First, displacement of the stimulating electrode from the supraorbital to zygomatic area shortened the latency of the evoked response. Second, these responses were stable (jitter mean consecutive difference < 25 microsec) and they had complex potential shapes unmodified by high-frequency stimulation. Finally, collision techniques demonstrated antidromic conduction of impulses in the facial nerve from supraorbital to zygomatic points. Therefore, these "R1-like" responses are not the early component of a functionally recovered blink reflex but motor axon reflexes or ephaptic responses similar to the short latency responses observed following facial nerve regeneration or from sutured nerves in human forearms.

Adolescent↗
PubMed1994

Exteroceptive reflexes in dystonia: a study of the recovery cycle of the R2 component of the blink reflex and of the exteroceptive suppression of the contracting sternocleidomastoid muscle in blepharospasm and torticollis.

The recovery cycle of the R2 component of the blink reflex and the exteroceptive suppression of EMG activity in the contracting sternocleidomastoid muscle produced by electrical stimulation of the supraorbital nerve were studied in normal subjects and in patients with either blepharospasm or torticollis. The latencies of the reflexes were normal, suggesting that the neural structures that mediated them were intact. However, the recovery of the R2 component of the blink reflex was enhanced in patients with either blepharospasm or torticollis. Also, the size of the exteroceptive suppression of the sternocleidomastoid muscle was reduced in both groups of patients. Our results are indicative of abnormalities of interneurons mediating exteroceptive reflexes in patients with craniocervical dystonia that are not restricted to the systems controlling the muscle involved in the dystonia.

Adult↗
PubMed1998

Choledochosphincter inhibitory reflex: identification of the reflex in dogs and its significance.

BACKGROUND: The sphincter of Oddi (SO) may undergo functional disorders. The mechanism of action of this sphincter is as yet not fully explored; the current study aims at studying some aspects of this mechanism. METHODS: Twelve mongrel dogs (mean weight 15.3 +/- 2. 9 SD kg, 8 male, 4 female) were studied. Under general anesthesia, the abdomen was opened and the gall bladder, common bile duct (CBD), and duodenum were exposed. Through separate punctures in the CBD, a balloon-tipped 2F catheter was introduced into the CBD and a 2F manometric catheter was placed within the SO. The positioning of the catheters was controlled fluoroscopically. The pressure response of the CBD and SO to CBD balloon distension with CO2, without and with separate anesthetization of either the CBD or SO, was recorded. RESULTS: Upon CBD distension by 0.5 ml of CO2, the pressure in the CBD rose (P < 0.001) and in the SO dropped (P < 0.01). The SO pressure drop was momentary and did not change significantly (P > 0. 05) with increase in the volume of CBD distension. The pressure response was blocked on separate anesthetization of the CBD and SO. CONCLUSIONS: The SO opening on CBD distension is suggested to be reflex and not hydromechanical. It seems to be mediated through a reflex which we call "choledochosphincter inhibitory reflex." Derangement of this reflex might result in functional disorders of the SO.

Anesthesia↗
PubMed1989

Studies on the rectoanal reflex in children and in experimental animals: an evaluation of neuronal control of the rectoanal reflex.

A single-chamber pressure probe for rectal electromanometry was developed which seems to be superior to the complicated multichamber systems not only for clinical but also for experimental purposes. Measurements of rectoanal reflex were carried out in 268 cases with abnormal bowel function, in 103 cases following operation for Hirschsprung's disease, and in 61 cases of imperforate anus to assess postoperative continence. Experimental studies were performed in 36 dogs, 27 of which were used for short-term and 9 for long-term studies. The results of clinical and experimental studies are described and discussed, with accompanying literature. From clinical and experimental studies, the neuronal pathways of the rectoanal reflex are schematized. The normal rectoanal reflex is mediated by both the sacral cord and the myenteric neurons. It is concluded that measurements of the anal resting pressure and the rectoanal reflex constitute a valuable method to distinguish between normal and pathological sacral and myenteric innervation.

Anal Canal↗
PubMed1999

Evidence suggesting that a transcortical reflex pathway contributes to cutaneous reflexes in the tibialis anterior muscle during walking in man.

Stimulation of cutaneous foot afferents has been shown to evoke a facilitation of the tibialis anterior (TA) EMG-activity at a latency of 70-95 ms in the early and middle swing phase of human walking. The present study investigated the underlying mechanism for this facilitation. In those subjects in whom it was possible to elicit a reflex during tonic dorsiflexion while seated (6 out of 17 tested), the facilitation in the TA EMG evoked by stimulation of the sural nerve (3 shocks, 3-ms interval, 2.0-2.5x perception threshold) was found to have the same latency in the swing phase of walking. The facilitation observed during tonic dorsiflexion has been suggested to be -- at least partly -- mediated by a transcortical pathway. To investigate whether a similar mechanism contributes to the facilitation observed during walking, magnetic stimulation of the motor cortex (1.2x motor threshold) was applied in the early swing phase at different intervals in relation to the cutaneous stimulation in 17 subjects. In 13 of the subjects, the motor potentials evoked by the magnetic stimulation (MEPs) were more facilitated by prior sural-nerve stimulation (conditioning-test intervals of 50-80 ms) than the algebraic sum of the control MEP and the cutaneous facilitation in the EMG when evoked separately. In four of these subjects, a tibialis anterior H-reflex could also be evoked during walking. In none of the subjects was an increase of the H-reflex similar to that for the MEP observed. In five experiments on four subjects, MEPs evoked by magnetic and electrical cortical stimulation were compared. In four of these experiments, only the magnetically induced MEPs were facilitated by prior stimulation of the sural nerve. We suggest that a transcortical pathway may also contribute to late cutaneous reflexes during walking.

Action Potentials↗
PubMed1975

Amygdala and masseteric reflex. II Mechanism of the diphasic modifications of the reflex elicited from the "defence reaction area". Role of the spinal trigeminal nucleus (pars oralis).

It has been demonstrated (Gary Bobo and Bonvallet 1975) that long-lasting stimulation of the "amygdaloid area for the defence reaction" (basal nucleus, pars magnocellularis) elicits, after an initial facilitation, a delayed inhibition of the monosynaptic masseteric reflex (MR), while stimulation of the amygdalofugal fibers running in the ansa lenticularis provokes an immediate inhibition of the reflex. In present study, the structure which mediates these inhibitions has been identified. Using combined techniques of limited transections, localized coagulations and localized stimulation and recording, it has been demonstrated that these ingibitions are mediated by the rostral portion of the spinal trigeminal nucleus, the subnucleus oralis (NO). After localized coagulation of this nucleus, or after lesions which interrupt slectively the connections between the NO and the masticatory nucleus, long-lasting stimulation of the basal nucleus elicits only well maintained facilitation of the MR. Hence, the delayed decrease in amplitude of the reflex, observed during stimulation of the basal nucleus in the preparations with intact brain, cannot be explained by the reversal of an initial facilitatory influence to an ingibitory one. The one ingibition of the reflex is due to the superimposition, on a background of sustained facilitation of the masseteric motoneurons, of the inhibitory influence exerted on the monosynaptic masseteric circuit by a trigeminal sensory nucleus, itself activated by delayed discharges of the basal nucleus. A tentative representation of the dual control exerted on the masseteric activity by the basal nucleus is given in Fig. 9. The functional implications of this dual control during the "defence reaction" are briefly discussed.

Amygdala↗
PubMed1993

Vesicolevator reflex. Description of a new reflex and its clinical significance.

A new reflex which I call "vesicolevator reflex" was studied in 21 healthy volunteers with a mean age of 36.3 years. The technique comprised the introduction of a catheter, with a balloon at its distal part, into the empty urinary bladder. A concentric needle electrode was inserted into the levator ani muscle. The vesical balloon was inflated with air in increments of 50 mL and the levator myoelectric activity recorded by a standard EMG apparatus. Vesical balloon was then removed, and levator EMG response to sudden suprapubic vesical compression was recorded with urinary bladder both empty and filled with saline in increments of 50 mL. Vesical balloon distention evoked levator muscle contraction; duration of contraction increased with increased vesical distention. Levator response to vesical distention did not occur when air-filling was below 50 mL air and when muscle was anesthetized. The latency of the reflex was calculated. Suprapubic manual compression of the empty urinary bladder did not cause levator contraction; yet, compression of distended bladder evoked the response. Compression should be sudden, while the patient is lying supine. Slow insidious compression did not evoke levator contraction. The vesicolevator reflex seems to play a role in the act of micturition, and hence could serve as a tool in investigating patients with micturition disorders.

Abdominal Muscles↗
PubMed1983

Reinforcement of tonic vibration reflex and exteroceptive vibration-induced flexion reflex in finger flexion muscles by forced respiration.

The effects of forced respiration on tonic vibration reflex (TVR) and exteroceptive vibration-induced flexion reflex (VFR) were studied in healthy man. vibration (100 Hz) applied to finger flexion muscles or the volar side of the middle finger induced a slowly augmenting facilitation of the TVR, which has mono-and polysynaptic components, and VFR, which is polysynaptic. Forced inspiration and forced expiration facilitated these slowly augmenting processes in both reflexes. Respiration reinforces both proprioceptive and exteroceptive reflexes elicited by vibration.

Adult↗
PubMed1981

Basal and reflex human tear analysis. I. Physical measurements: osmolarity, basal volumes, and reflex flow rate.

Minimally stimulated, retained "basal' tears and stimulated reflex tears were collected from normal controls, keratoconjunctivitis sicca (KCS) patients, and contact lens (CL) wearers. Basal tear samples were collected on small filter paper strips (Periopaper) over a five-second period, and volume was measured by means of an electronic device (Periotron). Collected basal tear volumes for KCS patients (0.84 +/- 0.42 mul) were significantly lower (P less than 0.01) than normal controls (1.18 +/- 0.36) and CL wearers (1.24 +/- 0.27). Reflex tear flow rates were measured over a five-minute period on Schirmer strips. Volume was calculated by comparison of wet length with known volumes of 1% egg white lysozyme solution. The reflex tear flow rates in KCS patients (3.29 +/- 3.57 mul/minute) were significantly lower than normal controls (5.71 +/- 5.86) and CL wearers (6.96 +/- 6.07). The elevation in CL wearers was not statistically significant when compared to normals. KCS patients are deficient in both basal and reflex tears compared to normals but have a more significant deficiency of basal tears. Female normals and CL wearers over 40 years of age have a higher tear osmolarity than those under 41 years of age. Female KCS patients over 40 years of age have a tear osmolarity that is not significantly different from female KCS patients under 41 years of age.

Adult↗
PubMed1996

Vibration-induced finger flexion reflex and inhibitory effect of acupuncture on this reflex in cervical spinal cord injury patients.

The vibration-induced finger flexion reflex (VFR) and the inhibitory effect of acupuncture on this reflex were studied in five cervical spinal cord injury patients (C-SCIs). VFR, which is a tonic finger flexion reflex induced by vibratory stimulation on the finger tip, was induced before and after acupuncture was carried out on the same hand. A stainless steel needle was inserted to the Hoku point. As in healthy subjects, VFR was performed and it was significantly inhibited by acupuncture in the C-SCIs; mean maximum VFR was 204.2 +/- S.E. 68.6 g before and 119.8 +/- S.E. 42.2 g after acupuncture. The present results suggest that at least part of the reflex center for VFR is located in the spinal cord and that part of VFR inhibition by acupuncture may be mediated via the spinal cord.

Acupuncture Therapy↗
PubMedDate not supplied

Role of the cervico-ocular reflex in the "flying" pigeon: interactions with the optokinetic reflex.

We studied the cervico-ocular reflex (COR) alone and in combination with the optokinetic (OKN) reflex in head-fixed pigeons. We analyzed these responses in two behavioral conditions: (1) animals were hung in a harness ("resting" condition); and (2) animals were additionally submitted to a frontal airflow that provoked a flight posture ("flying" condition). In both conditions, cervical stimulation provoked a slow phase of very low gain (around 0.05) in the opposite direction to that of the stimulation and fast phases triggered near the head-body alignment in the same direction as the stimulation. The slow phase showed a phase lag of 20 deg at 0.5 Hz. The gain of the slow phase was not modified by the velocity, amplitude, or frequency of the stimuli. This gain was not changed by the presence of a fixed visual surround. When cervical stimuli (0.05-0.5 Hz) were added to an optokinetic stimulation (30 deg/s) in the "resting" condition, the slow phase velocity (SPV) of the optokinetic reflex was modulated with a time course close to that produced by the cervico-ocular reflex alone. The SPV was alternately increased and decreased round the SPV level corresponding to the steady-state OKN. In the "flying" condition, optokinetic-cervical stimulation provoked an eye beating field and a strong SPV modulation synchronized with the position of the cervical stimulation. The number of nystagmic beats (OKN) and the amplitude and velocity of the fast phases were modulated in correlation with the SPV. Consequently, the optokinetic response was increased or decreased according to whether the cervical stimuli were in the reverse direction or in the same direction as the optokinetic stimulation, respectively. These data are interpreted as an improvement of gaze stabilization by the COR. This mechanism is context dependent, since it is strongly reinforced during the flight.

Animals↗
PubMed1990

Effects of brainstem lesions on the masseter inhibitory reflex. Functional mechanisms of reflex pathways.

The masseter inhibitory reflex (MIR) was investigated in 16 patients with localized brainstem lesions involving the trigeminal system. The MIR consists of two phases of EMG silence (S1 and S2) evoked by stimulation of the mental nerve during maximal clenching of the teeth. The extent of the lesions was assessed by neurological examination, nuclear magnetic resonance imaging (MRI), and recording of trigeminal reflexes with known paths (jaw jerk and blink reflex). The MIR appeared to be abnormal in lesions involving the pontine tegmentum, from the pontomedullary junction to midpons, and some lesions selectively affected one component of the MIR, proving that S1 and S2 are relayed by independent circuits. The results indicate that afferent fibres for S1, which reach the pons via the trigeminal sensory root, enter the ipsilateral trigeminal spinal tract and terminate at the level of the midpons; impulses are then relayed by interneurons to the ipsilateral and contralateral trigeminal motor nuclei. The afferent fibres for S2 follow a similar path, but descend to the pontomedullary junction; at this level impulses are conducted along bilateral interneuronal paths, which probably ascend through the lateral reticular formation, before connecting with the trigeminal motor nucleus on either side. Analysis of MIR recordings can be of particular value because brainstem inhibitory reflexes cannot be tested by clinical examination.

Adult↗
PubMed2001

Trigeminocervical reflexes elicited by stimulation of the infraorbital nerve: head retraction reflex.

In the current study, the effects of stimulation of the infraorbital nerve (ION) on the trigeminocervical reflexes (TCRs), recorded from the posterior neck muscles, was investigated and the results were compared with the results recorded by stimulation of the supraorbital nerve (SON). TCRs obtained by stimulation of the ION was evaluated as the electrophysiologic counterpart of the head retraction reflex. Twenty normal control subjects, 10 men and 10 women, were enrolled in the study. The SON and the ION were stimulated by using a bipolar surface electrode. Results were recorded by using either concentric needle electrodes inserted into the semispinalis capitis muscle at the level of the third or fourth cervical vertebra or by surface electrodes placed at the C3 and C7 vertebrae on the midline. It was found that stimulation of the supraorbital and infraorbital branches of the trigeminal nerve had different reflexive effects on the posterior neck muscles. A stable positive (or negative-positive) wave, with a very early latency and high amplitude was always recorded after maximal stimulation of the ION, which could never be detected by stimulation of the SON. The C3 response of the TCR, evoked by SON stimulation was always evoked, by stimulation of the ION, at a low threshold. These findings suggest that the head retraction reflex is composed of two phases: inhibitory and excitatory. The early, fixed positive wave represents the general inhibition of the cranial and neck muscles, just before withdrawal of the face and head, from unexpected stimuli, which precedes the dense C3 response, demonstrating activation of the posterior neck muscles.

Adult↗
PubMed2001

The masseter reflex: postprocessing methods and influence of age and gender. Normative values of the masseter reflex.

OBJECTIVES: Normative values of the masseter reflex are scarce. We studied the latencies, amplitudes and side differences of the masseter reflex in 105 healthy volunteers between the ages of 5 and 78 years. METHODS: Latencies were calculated as the mean of 10 single sweeps and, simultaneously, measured from the summation curve. Short-term reproducibility was determined in 33 volunteers by retesting the reflex after 1 week. RESULTS: There was a positive correlation between age and latencies and a negative correlation between age and amplitude. Maximal normal latencies were 8.3 ms for men and 7.9 ms for women in the age group below 50 years and 9.1 and 9.2 ms for the age group above 50 years. Latency differences between the right and left sides of >0.4 ms for subjects aged below 50 years and >0.5 ms for subjects aged above 50 years exceeded the 95% confidence interval. Amplitudes did not depend on gender. Calculated as a percentage of the side with higher amplitude, differences above one third could be accepted as abnormal. CONCLUSION: The masseter reflex appears to be a stable and robust clinical test, if age and gender differences are taken into account.

Adolescent↗
PubMed1994

Uterocervical reflex: description of the reflex and its clinical significance.

The effect of uterine distension on the cervix was studied in 16 women (mean age 38.4 years). Carbon dioxide was infused, in increments up to 50 ml, into a condom-ended catheter introduced into the uterus. The response of uterine and cervical pressures to uterine distension was determined before and after anesthetizing the uterine body and the cervix, respectively. Upon slow uterine distension, the cervical pressure increased (p < 0.01), while the uterine pressure showed insignificant changes (p > 0.05). Rapid distension led to cervical pressure decrease (p < 0.01) and increase of uterine pressure (p < 0.01). The cervical pressure did not respond to slow or rapid inflation of the anesthetized uterus, neither did the anesthetized cervix respond to uterine inflation. A reflex relationship seems to exist between the uterine body when distended and the cervix, which we call 'uterocervical reflex'. The study demonstrates that the uterus behaves differently under physiologic and pathologic conditions. Upon slow uterine distension as in pregnancy, the uterus adapts by uterine dilatation and cervical tightening. In pathologic conditions which distend the uterus rapidly, the latter reacts with uterine contraction and cervical dilatation, discharging the uterine contents. Dysfunction of the uterocervical reflex may result in uterine and cervical disorders. The reflex may thus be included as a diagnostic tool in such disorders.

Adult↗
PubMed2001

Method for recording spinal reflexes in mice: effects of thyrotropin-releasing hormone, DOI, tolperisone and baclofen on monosynaptic spinal reflex potentials.

Mice were used to record the spinal reflex potentials and to examine the effects of some drugs upon them. In anesthetized mice, laminectomy was performed in the lumbo-sacral region, and monosynaptic reflex potential (MSR) and polysynaptic reflex potential were recorded from the L5 ventral root after stimulation of the L5 dorsal root. Thyrotropin-releasing hormone (TRH) and 1-(4-iodo-2,5-dimethoxyphenyl)-2-aminopropane hydrochloride (DOI) produced transient and long-lasting increases in the MSR amplitude, respectively. Tolperisone hydrochloride and baclofen produced transient and long-lasting MSR depressions, respectively. These results show that mice can be used to record spinal reflex potentials, and that it may be possible to study the spinal cord function of mutant and knockout mice using this method.

Amphetamines↗