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 271 records · Page 15Linked to original sources
PubMed1979

A reflex hammer for accurate measurement of reflex latency.

A hammer equipped with a piezo-electric crystal is suitable to measure fast tendon jerk latencies more accurately than a hammer equipped with a mechanical switching device. Measurements show that the hammer supplied with a piezo-electric crystal gives a pulse within 50 musec--at least 10 times faster than hammers supplied with a mechanical switch--which is negligible in comparison with the latency of any reflex response.

Electroencephalography↗
PubMed2000

Effect of adaptive plasticity of linear vestibulo-ocular reflex upon angular vestibulo-ocular reflex.

OBJECTIVE: The vestibulo-ocular reflex (VOR) produces compensatory eye movements during head movements. The VOR consists of the angular VOR and the linear VOR. The VOR is under adaptive control that corrects VOR performance when visual-vestibular mismatch arises during head movements. Most experiments concerning plasticity of the VOR have used the angular VOR. So far, there has been no investigation on the effect of adaptive plasticity of the linear VOR on the angular VOR. In this study, using a linear sled, we tested the hypothesis that the angular VOR is altered by changes in the linear VOR. METHODS: To modify the linear VOR, we used an adaptation paradigm. Eight subjects were translated sinusoidally at 0.125 Hz and 0.16 g peak acceleration along their inter-aural axis for 40 min, while viewing earth-fixed vertical stripes on the wall while wearing the binocular magnifying lenses. Six of the eight subjects showed an increase in linear VOR sensitivity after adaptation. Each of the six subjects who showed an increase in linear VOR sensitivity after adaptation also showed an increased angular VOR gain at 0.125 Hz. CONCLUSION: These results suggest that the linear VOR and the angular VOR share common neural pathways in such a way that a change in the synaptic efficacy of one pathway is accompanied by a commensurate change in the other.

Adaptation, Physiological↗
PubMed1983

Changes in segmental reflexes following chronic spinal cord hemisection in the cat. II. Conditioned monosynaptic test reflexes.

In a companion paper (Hultborn & Malmsten 1983) it was described that ventral root discharges to stimulation of peripheral nerves became larger on the side of a chronic spinal hemisection (left) than on the other side. In the present paper, based on the same experiments, conditioning of monosynaptic test reflexes was used to study changes of both excitatory and inhibitory effects on specified motoneuronal pools. Conditioning stimulation was given to IA afferents (reciprocal Ia inhibition, presynaptic inhibition of Ia fibers), high threshold muscle afferents, low and high threshold cutaneous afferents and motor axons (recurrent inhibition). A comparison of the efficacy of conditioning stimuli on the two sides showed that facilitatory effects were larger on the side of hemisection in a clear majority of cases. Inhibition was almost always either more efficient on the side of hemisection or equally efficient on the two sides. In control cats, facilitatory effects tended to be larger on the right side, while the results for inhibitory conditioning generally showed no clear side-bias. The increase in facilitatory effects after lesions may contribute to symptoms of spasticity.

Afferent Pathways↗
PubMed1993

Cardiopulmonary reflexes do not modulate exercise pressor reflexes during isometric exercise in humans.

Previous studies that measured reflex vasoconstrictor responses during isometric exercise have suggested that these responses were modulated by arterial and cardiopulmonary baroreflexes. The purpose of these experiments was to determine forearm vasoconstrictor responses to isometric handgrip alone and during two levels of cardiopulmonary baroreceptor unloading with lower body negative pressure (-5 and -10 mmHg LBNP). Handgrip combined with -5 mmHg LBNP produced vasoconstrictor responses that were significantly greater than the algebraic sum of the separate responses to handgrip and LBNP alone, thus confirming earlier studies. However, with -10 mmHg LBNP, the vasoconstrictor responses to LBNP plus handgrip were not different from the algebraic sum of the separate response to LBNP and handgrip alone. These results indicate that when the influence of cardiac baroreceptors was reduced to a greater degree (-10 mmHg LBNP) than in previous studies, no interaction was observed, whereas with less reduction (-5 mmHg LBNP) an apparent interaction was noted. These data, together with recent studies in which sympathetic nerve activity to the lower leg was measured during similar protocols, suggest nonlinearities in the relationship between sympathetic nerve activity and vasoconstrictor responses.

Adult↗
PubMed1996

Patency of infarct-related artery. Effect of restoration of anterograde flow on vagal reflexes. ATRAMI (Automatic Tone and Reflexes After Myocardial Infarction) Investigators.

BACKGROUND: In post-myocardial infarction (MI) patients, the restoration of anterograde flow in the infarct-related artery (IRA) significantly improves survival. Limitation of infarct size and increased electrical stability of the myocardium are likely operating mechanisms for this beneficial effect. We tested the hypothesis that patency of the IRA may enhance vagal reflexes, a factor known to affect electrical stability of the infarcted myocardium. METHODS AND RESULTS: Analysis of angiographic data was performed in 359 of 1284 post-MI patients enrolled in a multicenter prospective study within 8 weeks after the index MI. All the patients underwent baroreflex sensitivity (BRS) assessment by the phenylephrine method. The BRS of the entire population averaged 8.2+/-5.5 ms/mm Hg and was significantly related to age but not to ejection fraction (EF). One-, two-, and three-vessel disease was present in 138, 96, and 99 patients, respectively, while no coronary stenosis was observed in 26. IRA patency was documented in 234 patients (65%), while in the remaining 125 (35%), the artery remained occluded. Patients with occluded IRAs had more extensive coronary disease (2 to 3 vessels, 71% versus 46%, P<.01) and more depressed left ventricular (LV) function (LVEF, 48+/-13% versus 53+/-12%, P<.001). Patency of the IRA was associated with higher BRS values (BRS, 8.9+/-5.8 versus 7.1+/-4.7 ms/mm Hg, P<.005) and with a lower incidence (9% versus 18% P<.02) of markedly depressed BRS (<3 ms/mm Hg), a condition suggested by preliminary studies to be associated with an increased risk of post-MI mortality. The association between IRA patency and BRS was more evident in anterior than in inferior MI. Multivariate regression analysis showed that age of the patient and patency of the IRA were the major independent determinants of BRS, while LVEF was weakly related to BRS and only when analyzed as a categorized variable. CONCLUSIONS: The presence of an open IRA is associated with higher baroreflex sensitivity, and this effect is largely independent of limitation of infarct size by IRA patency. These data offer new insights into the mechanisms by which coronary artery patency may affect cardiac electrical stability and survival.

Adult↗
PubMed1997

From the foot-mouth reflex to the hand-mouth reflex. A continuum of responses to appendicular compression.

We studied the mouth opening response to appendicular compression in two groups of children. This study was performed with the intention of testing the semiologic role of the act of mouth opening following stimulation of various regions, based on the hand mouth reflex of Babkin. Group I was formed by 33 normal children who underwent monthly follow up assessments since birth; and group II consisted of 50 children older than 6 months of age, known to have a neurologic deficit and a neuro-psychomotor development equivalent to that of a child in the first trimester of life. We observed that the normal mouth opening response in group I was more pronounced following compression of the hand and forearm when compared to compression of the arm (p < 0.001). This response could persist for as long as the first 6 months of life. We were not able to elicit a mouth opening response following compression of the lower limb in this group. Among children from group II, we observed mouth opening responses to stimulation of all limb segments. Within the upper limb, the response was more pronounced following compression of the hand in comparison to the forearm (p < 0.01), and forearm in comparison to the proximal arm (p < 0.01). Stimulation of the foot was more effective in eliciting a mouth opening response when compared to equivalent stimulation of the lower leg (p < 0.05). However, there was no statistical difference when responses to stimulation of the lower leg and thigh were compared. The presence of the previously unreported foot-mouth response may serve as an indicator of central nervous system compromise and could be associated with a poorer prognosis. We believe that our observations of the specific foot-mouth response patterns may serve as a marker of early neuro-psychomotor development dysfunction during childhood.

Adolescent↗
PubMed2004

The effects of lead stimulus and reflex stimulus modality on modulation of the blink reflex at very short, short, and long lead intervals.

The blink reflex is modulated if a weak lead stimulus precedes the blink-eliciting stimulus. In two experiments, we examined the effects of the sensory modality of the lead and blink-eliciting stimuli on blink modulation. Acoustic, visual, or tactile lead stimuli were followed by an acoustic (Experiment 1) or an electrotactile (Experiment 2) blink-eliciting stimulus at lead intervals of -30, 0, 30, 60, 120, 240, 360, and 4,500 msec. The inhibition of blink magnitude at the short (60- to 360-msec) lead intervals and the facilitation of blink magnitude at the long (4,500-msec) lead interval observed for each lead stimulus modality was relatively unaffected by the blink-eliciting stimulus modality. The facilitation of blink magnitude at the very short (-30- to 30-msec) lead intervals was dependent on the combination of the lead and the blink-eliciting stimulus modalities. Modality specific and nonspecific processes operate at different levels of perceptual processing.

Acoustic Stimulation↗
PubMed2000

Reflex epilepsy and reflex seizures of the visual system: a clinical review.

Reflex epilepsy of the visual system is charecterised by seizures precipitated by visual stimuli. EEG responses to intermittent photic stimulation depend on the age and sex of the subject and on how stimulation is performed: abnormalities are commonest in children and adolescents, especially girls. Only generalised paroxysmal epileptiform discharges are clearly linked to epilepsy. Abnormal responses may occur in asymptomatic subjects, especially children. Photosensitivity has an important genetic component. Some patients are sensitive to patterns, suggesting an occipital trigger for these events. Myoclonus and generalised convulsive and nonconvulsive seizures may be triggered by visual stimuli. Partial seizures occur less often and can be confused with migraine. Although usually idiopathic, photosensitive epilepsy may occur in degenerative diseases and some patients with photosensitive partial seizures have brain lesions. Sunlight and video screens, including television, video games, and computer displays, are the commonest environmental triggers of photosensitive seizures. Outbreaks of triggered seizures have occurred when certain flashing or patterned images have been broadcast. There are regulations to prevent this in some countries only. Pure photosensitive epilepsy has a good prognosis. There is a role for treatment with and without antiepileptic drugs, but photosensitivity usually does not disappear spontaneously, and then typically in the third decade.

Adolescent↗
PubMed1975

[Level of oxytocin release induced by vaginal dilatation (Ferguson reflex) and vagal stimulation (vago-pituitary reflex) in lactating rats (author's transl)].

1. Vaginal dilatation for 30 seconds caused a rapid and brief increase in intramammary pressure which was equivalent to that evoked by 160 muU of oxytocin (Syntocinon) injected intravenously. 2. The rise in mammary pressure induced by the stimulation of the central end of a severed vagus nerve for 30 seconds (5 V, 0,5 ms, 50 HZ) was similar to the response obtained with an intravenous injection of 360 muU of oxytocin. 3. The vago-pituitary reflex leads to the liberation of large amounts of antidiuretic hormone which does not interfere with the effect of oxytocin on the mammary gland, since dexamethasone phosphate prevented the vasopressor effect without significantly affecting the increase in intramammary pressure.

Animals↗
PubMed1991

Reflex sympathetic dystrophy syndrome: consensus report of an ad hoc committee of the American Association for Hand Surgery on the definition of reflex sympathetic dystrophy syndrome.

This report proposes that reflex sympathetic dystrophy be defined as a pain syndrome in which the pain is accompanied by loss of function and evidence of autonomic dysfunction. In the clinical setting, this diagnosis is usually associated with other anatomic and psychological diagnoses and may be associated with a variety of systemic illnesses and medicolegal factors. All components should be assessed before a treatment plan is established. Priorities should go to emergency care, acute injuries, and systemic illness, psychiatric problems, and chronic anatomic problems, in that order. Early, accurate diagnosis improves prognosis.

Consensus Statements as Topic↗
PubMed1997

Vestibulo-ocular reflex and visual vestibulo-ocular reflex during sinusoidal rotation in children.

To clarify the relationship between vestibular and visual (optokinetic) stimuli in normal children, we investigated the vestibulo-ocular reflex (VOR) and visual VOR (VVOR). The subjects were 20 healthy children aged 3-6 years and 24 healthy adults aged 21-29 years. The VOR gains and phase were measured under two visual conditions: with eyes open in complete darkness and with eyes open in a lighted optokinetic drum. In both visual conditions, phase did not significantly differ between children and adults. In the dark, children presented a significantly larger gain than that of adults. In the optokinetic drum, however, the gain values of the children were almost the same as in adults. We suggest that the large VOR gain values of children may be due to immaturity of the inhibitory regulation system of the VOR.

Adult↗
PubMed1997

Functional changes of brainstem reflexes in Parkinson's disease. Conditioning of the blink reflex R2 component by paired and index finger stimulation.

Recovery curves of the R2 component of the blink reflex have been studied in 10 control subjects and 13 parkinsonian patients both after ipsilateral paired stimulation of the supraorbital nerve and after index finger stimulation. In control subjects, both types of conditioning induced a comparable marked inhibition lasting more than 600 ms. In parkinsonian patients, inhibition was reduced after both conditionings. However, differences appeared in the magnitude of the changes: after paired stimulation, it was less significant (ANOVA and post-hoc Duncan's test: p = 0.04) than after index finger stimulation (p = 0.002). In that latter situation, the more marked reduction in inhibition is interpreted, in the light of current physiologic knowledge, by hypoactivity of the Nucleus Reticularis Giganto Cellularis (NRGC) which would make less efficient inhibitory interneurones in the trigemino-facial pathway. The results are thus compatible with the suggestion that NRGC is made indirectly less active in Parkinson's disease.

Analysis of Variance↗
PubMed1989

The R3 component of the blink reflex in man: a reflex response induced by activation of high threshold cutaneous afferents.

Ten successive experiments were carried out in 10 volunteers to compare the physiological properties of R2 and R3 components of the blink reflex. The electrical activation threshold of the R3 component was found to be significantly higher than that of the R2 response and was more susceptible to anaesthetic blocking of the peripheral afferents. This result suggests that the R3 component is induced by the activation of a different population of peripheral afferents from the R2 component. A recovery cycle study performed using a double stimulus showed that R3 is inhibited to a greater extent and for a longer time than R2. The temporal relationship of R3 to the voluntarily produced blink demonstrates that R3 is not a voluntary response to electrical stimulation. In conclusion, these experiments support the existence of an independent R3 component and its relationship with the activation of small diameter and higher threshold afferent fibres, perhaps nociceptive ones.

Adult↗
PubMed1998

The effects of prepulse-blink reflex trial repetition and prepulse change on blink reflex modification at short and long lead intervals.

Prepulse inhibition and facilitation of the blink reflex are said to reflect different responses elicited by the lead stimulus, transient detection and orienting response respectively. Two experiments investigated the effects of trial repetition and lead stimulus change on blink modification. It was hypothesized that these manipulations will affect orienting and thus blink facilitation to a greater extent than they will affect transient detection and thus blink inhibition. In Experiment 1 (N = 64), subjects were trained with a sequence of 12 lead stimulus and 12 blink stimulus alone presentations, and 24 lead stimulus-blink stimulus pairings. Lead interval was 120 ms for 12 of the trials and 2000 ms for the other 12. For half the subjects this sequence was followed by a change in pitch of the lead stimulus. In Experiment 2 (N = 64), subjects were trained with a sequence of 36 blink alone stimuli and 36 lead stimulus-blink stimulus pairings. The lead interval was 120 ms for half the subjects and 2000 ms for the other half. The pitch of the lead stimulus on prestimulus trials 31-33 was changed for half the subjects in each group. In both experiments, the amount of blink inhibition decreased during training whereas the amount of blink facilitation remained unchanged. Lead stimulus change had no effect on blink modification in either experiment although it resulted in enhanced skin conductance responses and greater heart rate deceleration in Experiment 2. The present results are not consistent with the notion that blink facilitation is linked to orienting whereas blink inhibition reflects a transient detection mechanism.

Acoustic Stimulation↗