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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A number of cortical regions are involved in processing pain-related information. The SI and SII somatosensory cortices process mainly sensory discriminative attributes but also play an important role in recognition and memory of painful events. Regions such as SII and the posterior insula appear to be the first stations that house processes by which attention profoundly shapes both behavioral responses and subjective pain experience. We investigated the influence of directed attention on pain-induced oscillations and synchronization processes using magnetoencephalogram in combination with an oddball paradigm in 20 healthy subjects. The subject's task was to count rare painful electrical stimuli applied to one finger, while ignoring frequent stimuli at a different finger. A high detection ratio was observed for all blocks and subjects. Early evoked oscillations in the delta-band increased with higher stimulus intensity and directed attention, most prominently at contralateral sensorimotor sites. Furthermore, suppression and rebound of beta activity were observed after painful stimulation. Moreover, induced oscillatory activity in the high gamma-band increased with directed attention, an effect being significantly stronger for high compared with low stimulus intensity. Coupling analysis performed for this high gamma response revealed stronger functional interactions between ipsilateral and contralateral sites during attention. We conclude that pain-induced high-frequency activity in sensorimotor areas may reflect an attentional augmentation of processing, leading to enhanced saliency of pain-related signals and thus to more efficient processing of this information by downstream cortical centers.
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PMID:Attention to painful stimulation enhances gamma-band activity and synchronization in human sensorimotor cortex. 1772 41

Recent neuroimaging studies precised the functions of the brain regions included in the so-called "pain-matrix". They isolated brain structures mediating attentional, emotional, anticipatory, cognitive, and discriminative aspects of pain perception. Surprisingly, little attention was devoted to isolate the cerebral network associated with the motor response to pain. In this study, we used fMRI to measure BOLD signal changes in nine volunteers while they received low- (L-) and high- (H-) intensity painful electrical shocks on the (left) lower limb. High-intensity stimulation was associated with a significantly stronger pain sensation and with a pronounced motor (withdrawal) reflex. BOLD responses common to L- and H-stimulation intensities were found in the right prefrontal and right posterior parietal cortices. These did not correlate with subjective pain ratings and probably mediate attentional processes unrelated to pain intensity and withdrawal. In contrast, signal changes in insula, left SII cortices and right amygdala did correlate with pain ratings and are therefore likely to encode for pain intensity. High-intensity shocks selectively recruited a motor network, including vermis, MI, SI, and paracentral cortices bilaterally, right premotor, right SII and posterior cingulate cortices. These responses, assessed for the first time in a functional imaging study, emphazised on the presence of a motor component in what has been described as the pain-matrix. They should be considered as a motor component of pain-related processes activated in case of intense pain.
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PMID:Central representation of the RIII flexion reflex associated with overt motor reaction: an fMRI study. 1799 13

The aim of the study was to investigate if an abnormal brain response to pain exists in patients with myofascial pain syndrome (MPS) when stimulated in a hypersensitive myofascial trigger point (MTP). Event-related functional magnetic resonance imaging was used to characterize the brain response to pain evoked from an MTP. Activation patterns from patients were compared with those evoked from an equivalent site in healthy controls with stimulus intensity matched and pain intensity matched stimuli. Compared to healthy controls at matched stimulus intensity, patients experienced significantly higher pain intensity (hyperalgesia). The corresponding brain response revealed significantly enhanced somatosensory (SI, SII, inferior parietal, mid-insula) and limbic (anterior insula) activity and suppressed right dorsal hippocampal activity in patients compared with controls. At matched pain intensity, enhanced activity was found in the same somatosensory areas but not in limbic areas. Our results show that the hyperalgesic state observed in MPS patients was associated with abnormal hyperactivity in regions processing stimulus intensity and negative affect. We speculate that suppressed hippocampal activity might reflect stress-related changes in relation to chronic pain as an effective physical and emotional stressor.
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PMID:Central representation of hyperalgesia from myofascial trigger point. 1799 39

In the present study, we compared brain activations produced by pleasant, neutral and unpleasant touch, to the anterior lateral surface of lower leg of human subjects. It was found that several brain regions, including the contralateral primary somatosensory area (SI), bilateral secondary somatosensory area (SII), as well as contralateral middle and posterior insula cortex were commonly activated under the three touch conditions. In addition, pleasant and unpleasant touch conditions shared a few brain regions including the contralateral posterior parietal cortex (PPC) and bilateral premotor cortex (PMC). Unpleasant touch specifically activated a set of pain-related brain regions such as contralateral supplementary motor area (SMA) and dorsal parts of bilateral anterior cingulated cortex, etc. Brain regions specifically activated by pleasant touch comprised bilateral lateral orbitofrontal cortex (OFC), posterior cingulate cortex (PCC), medial prefrontal cortex (mPFC), intraparietal cortex and left dorsal lateral prefrontal cortex (DLPFC). Using a novel functional connectivity model based on graph theory, we showed that a series of brain regions related to affectively different touch had significant functional connectivity during the resting state. Furthermore, it was found that such a network can be modulated between affectively different touch conditions.
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PMID:Dynamic changes in brain activations and functional connectivity during affectively different tactile stimuli. 1800 Jul 54

Painful gastric distension is processed in a network consisting of brainstem, thalamus, insula, anterior cingulate cortex, (lateral) orbitofrontal and prefrontal cortex, superior temporal cortex and cerebellum. However, the role of primary and secondary somatosensory cortical regions (SI/SII) in the processing of visceral sensation or pain in general and gastric sensation in particular remains unclear. The aim of this study was to localize activations in the SI/SII area from our previously published functional brain imaging studies on gastric distension more precisely, using newly available cytoarchitectonic probability maps of SI/SII, implemented in the SPM Anatomy toolbox. In healthy volunteers, we found two clusters to be overlapping with SII (mainly the OP4 subregion) and, to a lesser extent, SI, although this overlap was small in size. In functional dyspepsia patients, we found two clusters to be overlapping with SII (mainly OP4), of which the cluster in the right hemisphere also overlapped with SI. These findings were confirmed in a conjunction analysis of both groups. Activation in right SI/SII was significantly higher in healthy volunteers when formally compared to patients. These results provide more detailed information on the brain processing of gastric sensation, supporting the hypothesis that SI/SII are involved. This is in line with some previously published studies on visceral sensation, but at variance with some other studies. Methodological differences between the brain imaging studies on gastric distension may account for these somewhat discrepant findings.
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PMID:The role of somatosensory cortical regions in the processing of painful gastric fundic distension: an update of brain imaging findings. 1808 7

In this study, 4 male Qigong masters (aged 60 +/- 12) who had Qigong practicing experience for more than 30 years were tested. By using the technique of fMRI, the change of brain function under the state of Qigong was observed through the peripheral pain stimulation generated by potassium penetrating method. The fMRI examination was running on a GE signa VH/3.0 T MRI machine and block design was used. The test was repeated several times, which was carried out before and 15 min after Qigong practicing. The heart and respiration rate of these 4 Qigong masters were monitored during the whole test. SPM2 was used for the data analysis, and the result showed that before Qigong practicing, besides SI and SII-insula regions, many other Brodmann areas, the cigulate cortex, the thalamus, and the cerebellum were all activated, while 15 min after that, the activated areas were decreased obviously, which were mainly at the SII-insula region and some other Brodmann areas. Since the SII-insula region was activated in both of these two states, further analysis of the response curve was focused on it. Its response amplitude under the state of Qigong (3.5%) was greater than that before Qigong (1.2%). Our result indicated that the main manifestation of brain functional change under Qigong was functional suppressing, but in some particular regions such as SII-insula region in our study, the response amplitude was increased. Further study of the exact physiological mechanism of Qigong is needed.
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PMID:fMRI study of pain reaction in the brain under state of "Qigong". 1818 80

The cingulate cortex (CC) as a part of the "medial" pain subsystem is generally assumed to be involved in the affective and/or cognitive dimensions of pain processing, which are viewed as relatively slow processes compared with the sensory-discriminative pain coding by the lateral second somatosensory area (SII)-insular cortex. The present study aimed at characterizing the location and timing of the CC evoked responses during the 1 s period after a painful laser stimulus, by exploring the whole rostrocaudal extent of this cortical area using intracortical recordings in humans. Only a restricted area in the median CC region responded to painful stimulation, namely the posterior midcingulate cortex (pMCC), the location of which is consistent with the so-called "motor CC" in monkeys. Cingulate pain responses showed two components, of which the earliest peaked at latencies similar to those obtained in SII. These data provide direct evidence that activations underlying the processing of nociceptive information can occur simultaneously in the "medial" and "lateral" subsystems. The existence of short-latency pMCC responses to pain further indicates that the "medial pain system" is not devoted exclusively to the processing of emotional information, but is also involved in fast attentional orienting and motor withdrawal responses to pain inputs. These functions are, not surprisingly, conducted in parallel with pain intensity coding and stimulus localization specifically subserved by the sensory-discriminative "lateral" pain system.
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PMID:Parallel processing of nociceptive A-delta inputs in SII and midcingulate cortex in humans. 1821 2

Magnetoencephalographic, electromyographic (EMG), work, and reaction time (RT) were recorded from nine subjects during visually triggered intermittent isometric contractions of the middle finger under two conditions: unloaded and loaded (30% of maximal voluntary contraction). The effect of muscle fatigue was studied over three consecutive periods under both conditions. In the loaded condition, the motor evoked field triggered by the EMG onset decreased with fatigue, whereas movement-evoked fields (MEFs) increased (P < 0.01). Fatigue was demonstrated in the loaded condition, since (i) RT increased due to an increase in the electromechanical delay (P < 0.002); (ii) work decreased from Periods 1 to 3 (P < 0.005), while (iii) the myoelectric RMS amplitude of both flexor digitorum superficialis and extensor muscles increased (P < 0.003) and (iv) during Period 3, the spectral deflection of the EMG median frequency of the FDS muscle decreased (P < 0.001). In the unloaded condition and at the beginning of the loaded condition, a parallel network including M1-S1, posterior SII-insular, and posterior cingulate cortices accounted for the MEF activities. However, under the effect of fatigue, medial insular and posterior cingulate cortices drove this network. Moreover, changes in the location of insular and M1-S1 activations were significantly correlated with muscle fatigue (increase of RMS-EMG; P < 0.03 and P < 0.01, respectively). These results demonstrate that a plastic network controls the strength of the motor command as fatigue occurs: sensory information, pain, and exhaustion act through activation of the medial insular and posterior cingulate cortices to decrease the motor command in order to preserve muscle efficiency and integrity.
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PMID:A dynamic network involving M1-S1, SII-insular, medial insular, and cingulate cortices controls muscular activity during an isometric contraction reaction time task. 1826 18

Little is known regarding how cognitive strategies help to modulate neural responses of the human brain in ongoing pain syndromes to alleviate pain. Under pathological pain conditions, any self-elicited contact with usually non-painful stimuli may become painful. We examined whether the human brain is capable of dissociating self-controlled from externally administered thermal hyperalgesia in the experimental capsaicin model. Using functional magnetic resonance imaging, 17 male subjects were investigated in a parametric design with heat stimuli at topically capsaicin-sensitized skin. In contrast to external stimulation, self-administered pain was controllable. For both conditions application trials without noticeable thermal stimulation were introduced and used as high-level baseline (HLB) to account for the capsaicin-induced ongoing pain and other covariables. Following subtraction of the HLB, the anterior insula and the anterior cingulate cortex (ACC) but not the somatosensory cortices maintained parametric neural responses to thermal hyperalgesia. A stronger pain-related activity increase during self-administered stimuli was observed in the posterior insula. In contrast, prefrontal cortex showed stronger increases to uncontrollable external heat stimuli. In the state of ongoing pain (capsaicin), pain-intensity-encoding regions (anterior insula, ACC) but not those with sensory discriminative functions (SI, SII) showed graded, pain-intensity-related neural responses in thermal hyperalgesia. Some areas were able to dissociate between self- and externally administered stimuli in thermal hyperalgesia, which might be related to differences in perceived controllability. Thus, neural mechanisms maintain the ability to dissociate external from self-generated states of injury in thermal hyperalgesia. This may help to understand how cognitive strategies potentially alleviate chronic pain syndromes.
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PMID:Dissociable neural activity to self- vs. externally administered thermal hyperalgesia: a parametric fMRI study. 1827 26

This study investigates the effects of noise distraction on the different components and sources of laser-evoked potentials (LEPs) whilst attending to either the spatial component (localisation performance task) or the affective component (unpleasantness rating task) of pain. LEPs elicited by CO2 laser stimulation of the right forearm were recorded from 64 electrodes in 18 consenting healthy volunteers. Subjects reported either pain location or unpleasantness, in the presence and absence of distraction by continuous 85 dBa white noise. Distributed sources of the LEP peaks were identified using Low Resolution Electromagnetic Tomography (LORETA). Pain unpleasantness ratings and P2 (430 ms) peak amplitude were significantly reduced by distraction during the unpleasantness task, whereas the localisation ability and the corresponding N1/N2 (310 ms) peak amplitude remained unchanged. Noise distraction (at 310 ms) reduced activation in the anterior cingulate cortex (ACC) and precuneus during attention to localisation and unpleasantness, respectively. This suggests a complimentary role for these two areas in the control of attention to pain. In contrast, activation of the occipital pole and SII were enhanced by noise during the localisation and unpleasantness task, respectively, suggesting that the presence of noise was associated with increased spatial attentional load. This study has shown selective modulation of affective pain processing by noise distraction, indicated by a reduction in the unpleasantness ratings and P2 peak amplitude and associated activity within the medial pain system. These results show that processing of the affective component of pain can be differentially modulated by top-down processes, providing a potential mechanism for therapeutic intervention.
Pain 2008 Sep 15
PMID:Selective modulation of nociceptive processing due to noise distraction. 1842 72


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