1,721,337 research outputs found
Anticipation of somatosensory and motor events increases centro-parietal functional coupling: an EEG coherence study
No full textObjective: Does functional coupling of centro-parietal EEG rhythms selectively increase during the anticipation of sensorimotor events composed by somatosensory stimulation and visuomotor task? Methods: EEG data were recorded in (1) 'simultaneous' condition in which the subjects waited for somatosensory stimulation at left hand concomitant with a Go (or NoGo) visual stimulus triggering (50%) right hand movements and in (2) 'sequential' condition where the somatosensory stimulation was followed (+ 1.5 s) by a visuomotor Go/NoGo task. Centro-parietal functional coupling was modeled by spectral coherence. Spectral coherence was computed from Laplacian-transformed EEG data at delta-theta (2-7 Hz), alpha (8-14 Hz), beta 1 (15-21 Hz), beta 2 (22-33 Hz), and gamma (34-45 Hz) rhythms. Results: Before 'simultaneous' sensorimotor events, centro-parietal coherence regions increased in both hemispheres and at all rhythms. In the 'sequential' condition, right centro-parietal coherence increased before somatosensory event (left hand), whereas left centro-parietal coherence increased before subsequent Go/NoGo event (right hand). Conclusions: Anticipation of somatosensory and visuomotor events enhances contralateral centro-parietal coupling of slow and fast EEG rhythms. Significance: Predictable somatosensory and visuomotor events are anticipated not only by synchronization of cortical pyramidal neurons generating EEG power in parietal and primary sensorimotor cortical areas (Babiloni C, Brancucci A, Capotosto P, Arendt-Nielsen L, Chen ACN, Rossini PM. Expectancy of pain is influenced by motor preparation: a high-resolution EEG study of cortical alpha rhythms. Behav. Neurosci. 2005a; 119(2):503-511; Babiloni C, Brancucci A, Pizzella V, Romani G.L, Tecchio F, Torquati K, Zappasodi F, Arendt-Nielsen L, Chen ACN, Rossini PM. Contingent negative variation in the parasylvian cortex increases during expectancy of painful sensorimotor events: a magneto-encephalographic study. Behav. Neurosci. 2005b; 119(2):491-502) but also by functional coordination of these areas. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved
Power spectrum analysis of the rectified electromyogram during gait for normals and patients.
No full textFacilitation of quadriceps activation is impaired following eccentric exercise
No full textContracting the knee flexor muscles immediately before a maximum voluntary contraction (MVC) of knee extension increases the maximal force that the extensor muscles can exert. It is hypothesized that this phenomenon can be impaired by muscle fiber damage following eccentric exercise [delayed onset muscle soreness (DOMS)]. This study investigates the effect of eccentric exercise and DOMS on knee extension MVC immediately following a reciprocal-resisted knee flexion contraction. Electromyography (EMG) was recorded from the knee extensors and flexors of 12 healthy men during knee extension MVCs performed in a reciprocal (maximal knee extension preceded by resisted knee flexion), and nonreciprocal condition (preceded by relaxation of the knee flexors). At baseline, knee extension MVC force was greater during the reciprocal condition (P < 0.001), whereas immediately after, 24 and 48 h after eccentric exercise, the MVC force was not different between conditions. Similarly, at baseline, the EMG amplitude of the quadriceps during the MVC was larger for the reciprocal condition (P < 0.001). However, immediately after, 24 and 48 h postexercise the EMG amplitude was similar between conditions. In conclusion, eccentric exercise abolished the facilitation of force production for the knee extensors, which normally occurs when maximum knee extension is preceded by activation of the knee flexors.</p
Inter-individual variability and the effect of catastrophizing 140 on the perception of thermal grill illusion
No full textThe Thermal Grill Illusion (TGI) has been suggested as a promising experimental model for studying paradoxical thermal painful sensation as present in e.g. neuropathic pain. The TGI can be evoked by simultaneous application of innocuous cold and warm temperatures. However, a large inter-individual variability has been reported for the provocation of painful TGI. So far, it is not known which factors contribute to this variability. The purpose of this study was to investigate the role of catastrophizing in the perception of thermal grill illusion. 37 healthy subjects were recruited (17 females and 20 males) and assessed using the pain catastrophizing scale. Subjects were asked to place the palm of their non-dominant hand on six bars interlaced with cold and warm temperatures of 20° and 40°, respectively. Subjects were also tested in a control condition where both uniformly warm (40°C) and cold (20°C) bars were presented. After each test, subjects were asked to report both the intensity and the unpleasantness of the stimulus using a visual analog scale (VAS). The scale ranged from 0 (no sensation) to 10 (unbearable pain) and where 4 indicated the pain threshold. Furthermore, the quality of the TGI was assessed. The VAS intensity scale was divided into two categories: Responders and Non Responders according to the perceived intensity of the TGI. Subjects who reported intensities ≥ 4 where classified as Responders and subjects who reported intensities < 4 where classified as Non-Responders. Ten subjects were found to be Responders (felt a painful TGI), while 27 were Non-Responders (felt a non-painful TGI). T-test analyses showed that Catastrophizing levels (p<.05) were significantly higher in the Responders as compared with the Non-Responders. Furthermore, positive correlations were found in subjects with high-levels of catastrophizing scores and VAS intensity (p<.0001) and VAS Unpleasantness (p<.01). Furthermore, both warm intensity (p<.005) and unpleasantness (p<.001) ratings were significantly higher (but not painful) in Responders as compared with Non-Responders. A large inter-individual variability was also observed in the quality of the responses. Only, 10% of the participants experienced a burning pain perception while 7.5% heat pain while a greater 60% experienced an alternation or warm/cold. The remaining 22.5% reported a mix of (tingling, freezing pain, heat no-pain, and warm). In conclusion, an inter-individual variability exists in perception of a TGI. Catastrophizing is a factor which may modulate some of the perceptual processes and underlie part of the inter-individual variability
Low-Threshold Motor Unit Twitch Force and Conduction Velocity Following Sub-Maximal Fatiguing Contractions
No full textEpigenetic alterations in prescription opioid misuse: New strategies for precision pain management
No full textPrescription opioids are used for some chronic pain conditions. However, generally, long-term therapy has unwanted side effects which may trigger addiction, overdose, and eventually cause deaths. Opioid addiction and chronic pain conditions have both been associated with evidence of genetic and epigenetic alterations. Despite intense research interest, many questions about the contribution of epigenetic changes to this typology of addiction vulnerability and development remain unanswered. The aim of this review was to summarize the epigenetic modifications detected in specific tissues or brain areas and associated with opioid prescription and misuse in patients who have initiated prescribed opioid management for chronic non-cancer pain. The review considers the effects of opioid exposure on the epigenome in central and peripheral tissues in animal models and human subjects and highlights the mechanisms in which opioid epigenetics may be involved. This will improve our current understanding, provide the basis for targeted, personalized pain management, and thus balance opioid risks and benefits in managing chronic pain
Correction to: Increase pain sensitivity during the four phases of the migraine cycle in patients with episodic migraine (Neurological Sciences, (2022), 43, 9, (5773-5775), 10.1007/s10072-022-06263-w)
No full textOriginally, an incorrect Abstract was included in the paper. Author decided to remove Abstract as this is a short paper. The original article has been corrected
Effect of exercise-induced fatigue on postural control of the knee
No full textMuscle fatigue is associated with reduced power output and work capacity of the skeletal muscle. Fatigue-induced impairments in muscle function are believed to be a potential cause of increased injury rates during the latter stages of athletic competition and often occur during unexpected perturbations. However the effect of fatigue on functionally relevant, full body destabilizing perturbations has not been investigated. This study examines the effect of muscle fatigue on the activation of the quadriceps and hamstrings to fast, full body perturbations evoked by a moveable platform. Surface electromyographic (EMG) signals were recorded from the knee extensor (vastus medialis, rectus femoris, and vastus lateralis) and flexor muscles (biceps femoris and semitendinosus) of the right leg in nine healthy men during full body perturbations performed at baseline and immediately following high intensity exercise performed on a bicycle ergometer. In each condition, participants stood on a moveable platform during which 16 randomized postural perturbations (eight repetitions of two perturbation types: 8 cm forward slides, 8 cm backward slides) with varying inter-perturbation time intervals were performed over a period of 2-3 min. Maximal voluntary knee extension force was measured before and after the high intensity exercise protocol to confirm the presence of fatigue. Immediately after exercise, the maximal force decreased by 63% and 66% for knee extensors and flexors, respectively (P<0.0001). During the post-exercise postural perturbations, the EMG average rectified value (ARV) was significantly lower than the baseline condition for both the knee extensors (average across all muscles; baseline: 19.7±25.4μV, post exercise: 16.2±19.4 μV) and flexors (baseline: 24.3±20.9 μV, post exercise: 13.8±11.0 μV) (both P<0.05). Moreover the EMG onset was significantly delayed for both the knee extensors (baseline: 132.7±32.9 ms, post exercise: 170.8±22.9 ms) and flexors (baseline: 139.1±38.8 ms, post exercise: 179.3±50.9 ms) (both P<0.05). A significant correlation (R(2)=0.53; P<0.05) was identified between the percent reduction of knee extension MVC and the percent change in onset time of the knee extensors post exercise. This study shows that muscle fatigue induces a reduction and delay in the activation of both the quadriceps and hamstring muscles in response to rapid destabilizing perturbations potentially reducing the stability around the knee.</p
The effect of six weeks endurance training on dynamic muscular control of the knee following fatiguing exercise
No full textThe aim of the study was to examine whether six weeks of endurance training minimizes the effects of fatigue on postural control during dynamic postural perturbations. Eighteen healthy volunteers were assigned to either a 6-week progressive endurance training program on a cycle ergometer or a control group. At week 0 and 7, dynamic exercise was performed on an ergometer until exhaustion and immediately after, the anterior-posterior centre of pressure (COP) sway was analyzed during full body perturbations. Maximal voluntary contractions (MVC) of the knee flexors and extensors, muscle fiber conduction velocity (MFCV) of the vastus lateralis and medialis during sustained isometric knee extension contractions, and power output were measured. Following the training protocol, maximum knee extensor and flexor force and power output increased significantly for the training group with no changes observed for the control group. Moreover, the reduction of MFCV due to fatigue changed for the training group only (from 8.6% to 3.4%). At baseline, the fatiguing exercise induced an increase in the centre of pressure sway during the perturbations in both groups (>10%). The fatiguing protocol also impaired postural control in the control group when measured at week 7. However, for the training group, sway was not altered after the fatiguing exercise when assessed at week 7. In summary, six weeks of endurance training delayed the onset of muscle fatigue and improved the ability to control balance in response to postural perturbations in the presence of muscle fatigue. Results implicate that endurance training should be included in any injury prevention program.</p
Modulation of trigeminal laser evoked potentials and laser silent periods by homotopical experimental pain.
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