Search results for " Reflex"
showing 10 items of 241 documents
Significance of passively induced stretch reflexes on achilles tendon force enhancement
1998
An in vivo buckle transducer technique was applied to study the reflex contribution to ATF enhancement during passive dorsiflexion stretches. Single stretches led to a linear ATF increase in the absence of an EMG reflex response, whereas clear ATF enhancement over the passive component occurred 13-15 ms after the onset of EMG responses. To quantify the reflexly induced increase in ATF, the stretched position was maintained. The mean reflex effect was two to four times greater than the passive stretch effect.
Evidence of a contralateral motor influence on reciprocal inhibition in man
1992
The role of contralateral movement on both H reflex and reciprocal inhibition was studied. In normal men H reflex was induced by median nerve stimulation. Reciprocal inhibition was achieved through stimulation of the antagonist radial nerve. On this basis the effects of contralateral arm movement were analized. Furthermore the putative influence of exteroceptive origin was also verified by means of digit stimulation. Results showed that contralateral arm movement did not affect H reflex amplitude; on the contrary, it was able to enhance reciprocal inhibition induced by extensors on flexors. Study of cutaneous afferents demonstrated that contralateral digit stimulation failed to elicit modif…
Anatomical correlates of ocular motor deficits in cerebellar lesions
2009
Humans are able to stabilize the images of moving targets on the retina by means of smooth pursuit eye movements. After the pontine level, all smooth pursuit pathways pass through the cerebellum. Previous animal studies gave evidence that two specific lesion sites within the cerebellum cause smooth pursuit disorders: those of the flocculus/paraflocculus and the vermis including lobule VI, VII, the uvula and the deep cerebellar nuclei. To date, there have been only a few lesion studies in patients with smooth pursuit disorders that do not allow direct comparison with a control group. In the present study, new lesion mapping techniques determined which cerebellar structures were involved in p…
The Primitive Palmomental Reflex in Amyotrophic Lateral Sclerosis
2017
<b><i>Background and Purpose:</i></b> The palmomental reflex (PMR) is a primitive reflex that might be released due to inhibition in adulthood. It has been associated with several neurodegenerative conditions. The aim of the present study was to evaluate the frequency of PMR in amyotrophic lateral sclerosis (ALS). <b><i>Patients and Methods:</i></b> Non-demented ALS patients (<i>n</i> = 179) were recruited. Two groups of disease controls were enrolled: (a) non-demented patients with other neurological disorders (NC;<i> n</i> = 86, mean age 60 ± 14 years); (b) healthy subjects, healthy controls (HC; <i>n</i> …
Short and long latency reflex responses elicited by electrical and mechanical stimulation in human hand muscle
1986
The relationship between electrically and mechanically induced reflex responses in the rectified, averaged surface electromyogram of the first interosseus dorsalis muscle was examined in 18 healthy human subjects. Both methods evoked identifiable short and long latency reflex responses. The onset latencies for short latency reflexes with electrical and mechanical stimulations were 30.6 ms (+/- 2.2 ms) and 28.9 ms (+/- 2.2 ms) and for long latency reflexes 50.0 ms (+/- 2.8 ms) and 51.2 ms (+/- 5.2 ms), respectively. The correlation of the onset latencies of the reflexes revealed significant correspondence between the electrical and mechanical methods implying at least partly mutual mechanism…
Heat-evoked vasodilatation in human hairy skin: axon reflexes due to low-level activity of nociceptive afferents.
1996
1. Spreading vasodilatation of the axon reflex type was evoked by contact heat stimulation of the hairy skin in the human forearm (13.3 cm2 stimulus area) and was detected by laser Doppler flowmetry at 8, 19 and 30 mm distance. 2. From a base temperature of 35 degrees C, rapidly rising short heat stimuli (4 degrees C s-1, 2 s plateau) elicited vasodilatation at an average threshold of 39.4 degrees C. For slowly rising sustained heat stimuli (64 s duration) the average threshold was 39.6 degrees C (n.s.) Laser Doppler flowmetry revealed a rapid onset within about 4 s, a long duration of several minutes beyond the end of the stimulus, and a rapid spread of vasodilatation to remote skin areas.…
Neuromuscular function during drop jumps in young and elderly males
2011
The Hoffman reflex (H-reflex), indicating alpha-motoneuron pool activity, has been shown to be task - and in resting conditions - age dependent. How aging affects H-reflex activity during explosive movements is not clear at present. The purpose of this study was to examine the effects of aging on H-reflexes during drop jumps, and its possible role in drop jump performance. Ten young (26.8 ± 2.7 years) and twenty elderly (64.2 ± 2.7 years) subjects participated in the study. Maximal drop jump performance and soleus H-reflex response (H/M jump) 20 ms after ground contact were measured in a sledge ergometer. Maximal H-reflex, maximal M-wave, Hmax/Mmax-ratio and H-reflex excitability curves wer…
Topodiagnostic value of blink reflex R1 changes: a digital postprocessing MRI correlation study.
2001
The aim of the study was to investigate the relation of the blink reflex R1 arc to known anatomical brainstem structures. Acute vascular brainstem lesions as identified by magnetic resonance imaging (MRI) of patients with isolated R1 pathology were superimposed into a stereotactic anatomical atlas using a new method of digital postprocessing. Isolated acute brainstem lesions were documented by diffusion-weighted MRI in 12 of 24 patients with unilateral R1 pathology. The lesions were located in the ipsilateral mid- to lower pons. In three patients only, the lesion had partial contact with the principal sensory nucleus of the trigeminal nerve (PSN) on at least one level. In two patients, the …
Withdrawal reflex organisation to electrical stimulation of the dorsal foot in humans.
2001
The present study investigated excitatory reflex receptive fields for various muscle reflex responses and reflex mediated ankle joint movements using randomised electrical stimulation of the dorsal and plantar surface of the foot in 12 healthy subjects. Eleven electrodes (0.5-cm2 cathodes) were mounted on the dorsal side and three on the plantar side of the foot. A low (1.5 times pain threshold) and a high (2.3 times pain threshold) stimulus intensity were used to elicit the reflexes. EMG signals were recorded from tibialis anterior (TA), gastrocnemius medialis (GM), soleus (SO), biceps femoris (BF), and rectus femoris (RF) muscles together with the ankle movement measured by a goniometer. …
Characterization of blink reflex interneurons by activation of diffuse noxious inhibitory controls in man.
1998
The blink reflex consists of an early, pontine R1-component and a late, medullary R2-component. R1 and R2 can be evoked by innocuous stimuli, but only the R2 also by painful heat, suggesting that the R2 is mediated by wide dynamic range neurons (WDR) of the spinal trigeminal nucleus. Remote noxious stimuli suppress the activity in WDR neurons via activation of diffuse noxious inhibitory controls (DNIC), whereas low-threshold mechanoreceptive neurons (LTM) are unaffected. In order to characterize the trigeminal interneurons of R1 and R2 we investigated the modulation of the blink reflex by remote painful heat. The blink reflex was elicited in 11 healthy subjects by innocuous electrical pulse…