Search results for "reflex"
showing 10 items of 622 documents
Effects of caffeine on neuromuscular function in a non‐fatigued state and during fatiguing exercise
2020
New findings What is the central question of the study? What are the effects of caffeine on neuromuscular function in a non-fatigued state and during fatiguing exercise? What is the main finding and its importance? In a non-fatigued state, caffeine decreased the duration of the silent period evoked by transcranial magnetic stimulation. Caffeine-induced reduction of inhibitory mechanisms in the central nervous system before exercise was associated with an increased performance. Individuals who benefit from caffeine ingestion may experience lower perception of effort during exercise and an accelerated recovery of M-wave amplitude postfatigue. This study elucidates the mechanisms of action of …
Isolated, subtle, neurological abnormalities in neurologically and cognitively healthy aging subjects
2015
The aim of this study is to describe the frequency of isolated, subtle, neurological abnormalities (ISNAs) in a large population of neurologically and cognitively healthy subjects and to compare ISNAs to various types of MRI-detected cerebrovascular lesions and subcortical brain atrophy in different age classes. 907 subjects were selected from a large, prospective hospital-based study. At baseline neurological examination, 17 ISNAs were selected. Primitive reflexes were the most common ISNAs (35.8 %), while dysphagia was the most rarely encountered (0.3 %). Measures of small vessel disease, i.e., deep and subcortical white matter hyperintensity and lacunar infarcts as well as subcortical at…
Nociceptive Primitive Reflexes in Neurologically and Cognitively Healthy Aging Subjects
2019
ABSTRACT:Background:To assess the prevalence of three nociceptive primitive reflexes (nPR), i.e., glabellar tap, snout reflex, and palmomental reflex, in neurologically and cognitively healthy (NCH) aging subjects.Objective:To investigate whether nPR are cross-sectionally associated with white matter hyperintensities (WMH), lacunes, atrophy of the caudate nuclei, and global brain atrophy.Methods:A total of 1246 NCH subjects aged 45–91 years were included in the study and underwent standard brain MRI. Atrophy of the caudate nuclei and global brain atrophy were assessed through the bicaudate ratio (BCr) and lateral ventricles to brain ratio (LVBr), respectively. WMH were assessed through visu…
Disturbed social behavior and motivation in rats selectively bred for deficient sensorimotor gating
2007
Deficient prepulse inhibition (PPI) of startle reflects disturbed sensorimotor gating found in certain neuropsychiatric disorders. We here tested whether rats selectively bred for deficient PPI are deteriorated in behavioral paradigms used to model negative symptoms of schizophrenia. Rats with low PPI preferred standard rat-chow when having the choice between lever-pressing for reward-pellets or freely available rat-chow, suggesting reduced motivation. Additionally, these rats show deteriorated social behavior during interaction with a juvenile rat. Rats selectively bred for low PPI may therefore be used as a model to study the biological mechanisms and therapeutic strategies of negative sy…
Modulation of spinal excitability by a sub-threshold stimulation of M1 area during muscle lengthening
2013
Abstract It is well known that the H-reflex amplitude decreases during passive muscle lengthening in comparison with passive shortening. However, this decrease in spinal synaptic efficacy observed during passive lengthening seems to be lesser during eccentric voluntary contraction. The aim of the present study was to examine whether spinal excitability during lengthening condition could be modulated by magnetic brain stimulation. H reflexes of the triceps surae muscles were elicited on 10 young healthy subjects, and conditioned by a sub-threshold transcranial magnetic stimulation (TMS). The conditioning stimulation was applied over the M1 area of triceps surae muscles at an intensity below …
Effects of short term water immersion on peripheral reflex excitability in hemiplegic and healthy individuals: A preliminary study
2016
Background: Reflex excitability is increased in hemiplegic patients compared to healthy controls. One challenge of stroke rehabilitation is to decrease the effects of hyperreflexia, which may be possible with water immersion. Methods/Aims: The present study examined the effects of acute water immersion on electrically-evoked Hmax:Mmax ratios (a measure of reflex excitability) in 7 hyperreflexive hemiplegic patients and 7 age-matched healthy people. Hmax:Mmax ratios were measured from soleus on dry land (L1), immediately after (W1) and 5 minutes after immersion (W5), and again after five minutes on land (L5). Results: Water immersion led to an acute increase in Hmax:Mmax ratio in both groups…
Long-lasting handling affects behavioural reactivity in adult rats of both sexes prenatally exposed to diazepam
2001
Environmental stressors can substantially affect the adaptive response of rats to novelty in a sexually dimorphic manner. Gender-related differences are also observed in neurochemical and behavioural patterns of adult rats following prenatal exposure to diazepam (DZ). In the present study the behavioural reactivity to novelty is investigated in open field (OF) and in acoustic startle reflex (ASR) tests, in non handled (NH), short-lasting handled (SLH) and long-lasting handled (LLH) adult male and female rats prenatally exposed to DZ. A single daily s.c. injection of DZ (1.5 mg/kg) over gestation days 14-20 decreases GABA/BDZ receptor function in both sexes, as shown by the decreased electro…
Effect of recurrent yohimbine on immediate and post-hoc behaviors, stress hormones, and energy homeostatic parameters
2013
Evidence from experimental models has suggested that acute activation of brain stress and anxiety pathways impacts subsequent behaviors that are mediated or modulated by limbic circuitry. There have been limited investigations of prior or chronic activation of these pathways on subsequent limbic-mediated behaviors. In this study, we tested whether recurrent administration of the anxiogenic compound yohimbine (YOH) could have post-injection effects on brain activation, stress hormones, and performance in sucrose self-administration and startle response paradigms. Rats received six injections across two weeks of either 2mg/kg YOH or saline. Behavioral evaluation confirmed the continued effica…
Chemosensory anxiety signals prime defensive behavior in prepubertal girls
2017
indexation en cours; Chemosensory anxiety signals effectively prime motor responses related to withdrawal behavior, such as the startle reflex, in adult humans. As the reproductive status strongly affects the response to social chemosignals, the current study examined whether chemosensory anxiety signals would augment the startle response in prepubertal children as it does in adults. Using cotton pads, axillary sweat was collected from 28 men while waiting for an important oral examination (anxiety condition), and during ergometer training (sport control condition). Using a constant-flow olfactometer, sweat samples and pure cotton samples (cotton control) were presented to 10 prepubertal gi…
Genetic variation in neuromuscular performance.
1973
Using a simple cumulative model of heredity plus environment, based on intrapair differences observed in monozygous (MZ) and dizygous (DZ) twins, the relative contribution of heredity to the interindividual variance in several neuromuscular parameters was determined with 15 pairs of male (8 MZ and 7 DZ) and 14 pairs of female (7 MZ and 7 DZ) twins ranging in age from 10 to 14 years. The data disclosed that in boys the variability in maximal mechanical (anaerobic) power was 99.2% genetically determined under the environmental conditions of the study. The corresponding heritability estimate values for the patellar reflex time and reaction time were 97.5% and 85.7%, respectively. In girls the …