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321.
Psychophysical experiments were carried out on 16 human subjects to determine how low intensity mechanical and thermal skin stimuli interfere with the sensation of pain. Moderate or intense pain was induced by low frequency (2 Hz) electrical stimulation within cutaneous fascicles of the median nerve at wrist level, and vibration, pressure, cooling or warming were applied for short periods (usually 20-60 sec) within or outside the skin area to which the pain was projected. Vibration within the area of projected pain reduced the sensation of pain more efficiently than vibration outside that area. Moderate pain was sometimes completely inhibited but intense pain was only moderately reduced. Pressure and cooling produced some pain relief whereas mild warming had an ambiguous effect. Since the painful input derived from stimulation of fibres in the nerve trunk, and not from peripheral nociceptors, the pain suppressing effects of vibration and cooling are not explicable in terms of lowered excitability of the nociceptive nerve endings in the skin. Instead, the results indicate that activity in low threshold mechanoreceptive and cold sensitive units suppresses pain at central (probably segmental) levels.  相似文献   
322.
Neonatal electroencephalography (EEG) presents a challenge due to its difficult interpretation that differs significantly from interpretation in older children and adolescents. Also, from the technological point of view, it is more difficult to perform and is not a standard procedure in all neonatal intensive care units (NICUs). During recent years, long-term cerebral function monitoring by the means of amplitude-integrated EEG (aEEG) has become popular in NICUs because it is easy to apply, allows real-time interpretation by the neonatologist treating the newborn, and has predictive value for outcome. On the other side, to record conventional EEG (cEEG), which is still considered the gold standard of neonatal EEG, the EEG technician should not only be well trained in performing neonatal EEG but also has to adapt to suboptimal working conditions. These issues need to be understood when approaching the neonatal cEEG in NICU and the main structure of the article is dedicated to this technique. The authors discuss the benefits of the digitalization and its positive effects on the improvement of NICU recording. The technical aspects as well as the standards for cEEG recording are described, and a section is dedicated to possible artifacts. Thereafter, alternative and concomitant use of aEEG and its benefits are briefly discussed. At the end there is a section that presents a review of our own cEEG and aEEG recordings that were chosen as the most frequently encountered patterns according to Consensus statement on the use of EEG in the intensive care unit.  相似文献   
323.
Repetitive transcranial magnetic stimulation (rTMS) appears to have effects on cortical excitability that extend beyond the train of rTMS itself. These effects may be inhibitory or facilitatory and appear to depend on the frequency, intensity, duration and intertrain interval of the rTMS. Many studies assume facilitatory effects of high-frequency rTMS and inhibitory effects of low-frequency rTMS. Nevertheless, the interindividual variability of this modulation of cortical excitability by rTMS has not been systematically investigated. In this study, we applied 240 pulses of rTMS at 90% of the subjects' motor threshold to their motor cortex at different frequencies (1, 10, 15 and 20 Hz) and examined the effects on motor evoked potentials (frequency tuning curve). Although the averaged group data showed a frequency-dependent increase in cortical excitability, each subject had a different pattern of frequency tuning curve, i.e. a different modulatory effect on cortical excitability at different rTMS frequencies. The interindividual variability of these modulatory effects was still high, though less so, when the number of rTMS pulses was increased to 1,600. These findings illustrate the degree of variability of the rTMS effects in the human brain.  相似文献   
324.
Early forms of complex regional pain syndromes (CRPS) are characterized by severe pain and autonomic dysfunction in a limb, both of which seem out of proportion to the inciting event. While often caused by obvious nerve injury, the syndromes also occur following relatively trivial trauma. Persistent inflammation has been implicated in the etiology of CRPS. We hypothesized that inflammation of a nerve proximal to the symptoms could lead to neural changes consistent with clinical CRPS. Using a rat model of neuritis, the activity of sensory and autonomic neurons was recorded distal to the inflamed site using single fiber electrophysiological methods. In normal rats, no sensory neurons had ongoing activity. The discharge rate of sympathetic postganglionic neurons was 2.26 ± 1.33 Hz (mean ± SD). However, in rats with inflamed nerves, 27% of slowly conducting neurons had ongoing activity after 3–4 days, and 50% had such activity after 7–8 days. Other sensory neurons did not exhibit ongoing activity. Sympathetic postganglionic neurons had a significantly slower ongoing discharge rate during inflammation (1.96 ± 1.19 Hz after 3–4 days, 1.48 ± 1.23 Hz after 7–8 days). Additionally, none of the sympathetic axons in any group were mechanically sensitive. These findings support that focal nerve inflammation is sufficient to cause neuronal discharge changes that are consistent with clinical findings in early CRPS. Furthermore, the lack of axonal mechanical sensitivity in sympathetic axons rules out channels expressed in these neurons as possible mechano-electrical transducers.  相似文献   
325.
The objective of this appraisal is to shed light on the various approaches to screen sensory information in the human gut. Understanding and characterization of sensory symptoms in gastrointestinal disorders is poor. Experimental methods allowing the investigator to control stimulus intensity and modality, as well as using validated methods for assessing sensory response have contributed to the understanding of pain mechanisms. Mechanical stimulation based on impedance planimetry allows direct recordings of luminal cross-sectional areas, and combined with ultrasound and magnetic resonance imaging, the contribution of different gut layers can be estimated. Electrical stimulation depolarizes free nerve endings non-selectively. Consequently, the stimulation paradigm (single, train, tetanic) influences the involved sensory nerves. Visual controlled electrical stimulation combines the probes with an endoscopic approach, which allows the investigator to inspect and obtain small biopsies from the stimulation site. Thermal stimulation (cold or warm) activates selectively mucosal receptors, and chemical substances such as acid and capsaicin (either alone or in combination) are used to evoke pain and sensitization. The possibility of multimodal (e.g. mechanical, electrical, thermal and chemical) stimulation in different gut segments has developed visceral pain research. The major advantage is involvement of distinctive receptors, various sensory nerves and different pain pathways mimicking clinical pain that favors investigation of central pain mechanisms involved in allodynia, hyperalgesia and referred pain. As impairment of descending control mechanisms partly underlies the pathogenesis in chronic pain, a cold pressor test that indirectly stimulates such control mechanisms can be added. Hence, the methods undoubtedly represent a major step forward in the future characterization and treatment of patients with various diseases of the gut, which provides knowledge to dinicians about the underlying symptoms and treatment of these patients.  相似文献   
326.
Neurophysiological studies on children and adults with dyslexia provide a deeper understanding of how visual and auditory processing in dyslexia might relate to reading deficits. The goal of this review is to provide an overview of research findings in the last two decades on motion related and contrast sensitivity visual evoked potentials and on auditory event related potentials to basic tone and speech sound processing in dyslexia. These results are particularly relevant for three important theories about causality in dyslexia: the magnocellular deficit hypothesis, the temporal processing deficit hypothesis and the phonological deficit hypothesis. Support for magnocellular deficits in dyslexia are primarily provided from evidence for altered visual evoked potentials to rapidly moving stimuli presented at low contrasts. Consistently ERP findings revealed altered neurophysiological processes in individuals with dyslexia to speech stimuli, but evidence for deficits processing certain general acoustic information relevant for speech perception, such as frequency changes and temporal patterns, are also apparent.  相似文献   
327.
《Clinical neurophysiology》2021,132(11):2896-2906
ObjectiveNeurophysiological investigation of nociceptive pathway has so far been limited to late cortical responses. We sought to detect early components of the cortical evoked potentials possibly reflecting primary sensory activity.MethodsThe 150 IDE micropatterned electrode was used to selectively activate Aδ intraepidermic fibres of the right hand dorsum in 25 healthy subjects and 3 patients suffering from trigeminal neuralgia. Neurographic recordings were performed to assess type of stimulated fibres and check selectivity. Cortical evoked potentials were recorded from C3′-Fz and Cz-Au1.ResultsNeurographic recordings confirmed selective activation of Aδ fibres. Early components were detected after repetitive stimulation (0.83/s rate and 250–500 averages); the first negative component occured at 40 ms (N40) on the contralateral scalp.ConclusionsThe provided data support the hypothesis that N40 could be the cortical primary response conducted by fast Aδ fibres.SignificanceThis is the first report of early, possibly primary, cortical responses in humans by nociceptive peripheral stimulation. Although not perfected yet to allow widespread diagnostic use, this is probably the only method to allow fully objective evaluation of the nociceptive system, with important future implications in experimental and clinical neurophysiology.  相似文献   
328.
《Clinical neurophysiology》2020,131(12):2809-2816
ObjectiveCoronavirus disease 2019 (COVID-19) has a high incidence of intensive care admittance due to the severe acute respiratory syndrome (SARS). Intensive care unit (ICU)-acquired weakness (ICUAW) is a common complication of ICU patients consisting of symmetric and generalised weakness. The aim of this study was to determine the presence of myopathy, neuropathy or both in ICU patients affected by COVID-19 and whether ICUAW associated with COVID-19 differs from other aetiologies.MethodsTwelve SARS CoV-2 positive patients referred with the suspicion of critical illness myopathy (CIM) or polyneuropathy (CIP) were included between March and May 2020. Nerve conduction and concentric needle electromyography were performed in all patients while admitted to the hospital. Muscle biopsies were obtained in three patients.ResultsFour patients presented signs of a sensory-motor axonal polyneuropathy and seven patients showed signs of myopathy. One muscle biopsy showed scattered necrotic and regenerative fibres without inflammatory signs. The other two biopsies showed non-specific myopathic findings.ConclusionsWe have not found any distinctive features in the studies of the ICU patients affected by SARS-CoV-2 infection.SignificanceFurther studies are needed to determine whether COVID-19-related CIM/CIP has different features from other aetiologies. Neurophysiological studies are essential in the diagnosis of these patients.  相似文献   
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