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

In recent years the rat knee joint has become an important model for the study of nociception of deep tissues. In contrast to the cortical processing of superficial pain, the knowledge about the processing of deep pain evoked by noxious stimuli in tissues such as tendons, bone, and joint is sparse. To obtain a basis for further functional studies, the projections of the knee joint in the cerebral cortex were determined. Cortical surface potentials evoked by electrical stimulation of the posterior articular nerve were recorded by a platinum ball electrode. Evoked activity was found in the primary somatosensory area SI in an area of about 3 x 3 mm on the contralateral side. Its center was located about 3 mm caudal to the bregma and about 3 mm lateral to the superior sagittal sinus. A small projection in SII was found on the lateral side of the cortex about 6 mm lateral from SI. This area had a size of about 1 x 1 mm, and the amplitudes of the potentials were smaller but had similar latencies to those in SI. An additional projection with small potentials and longer latencies was observed in SI on the ipsilateral side. Cooling of the contralateral SI revealed deprivation of the ipsilateral evoked potentials in SI whereas the potentials in SII remained unchanged. These data indicate that information from the knee joint is processed in parallel in SI and SII on the contralateral side and that there is an additional serial processing in SI on the ipsilateral side.
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PMID:Cortical projection of the rat knee joint innervation and its processing in the somatosensory areas SI and SII. 1181 Jan 43

The role of the somatosensory cortices (SI and SII) in pain perception has long been in dispute. Human imaging studies demonstrate activation of SI and SII associated with painful stimuli, but results have been variable, and the functional relevance of any such activation is uncertain. The present study addresses this issue by testing whether the time course of somatosensory activation, evoked by painful heat and nonpainful tactile stimuli, is sufficient to discriminate temporal differences that characterize the perception of these stimulus modalities. Four normal subjects each participated in three functional magnetic resonance imaging (fMRI) sessions, in which painful (noxious heat 45-46 degrees C) and nonpainful test stimuli (brushing at 2 Hz) were applied repeatedly (9-s stimulus duration) to the left leg in separate experiments. Activation maps were generated comparing painful to neutral heat (35 degrees C) and nonpainful brushing to rest. Directed searches were performed in SI and SII for sites reliably activated by noxious heat and brush stimuli, and stimulus-dependent regions of interest (ROI) were then constructed for each subject. The time course, per stimulus cycle, was extracted from these ROIs and compared across subjects, stimulus modalities, and cortical regions. Both innocuous brushing and noxious heat produced significant activation within contralateral SI and SII. The time course of brush-evoked responses revealed a consistent single peak of activity, approximately 10 s after the onset of the stimulus, which rapidly diminished upon stimulus withdrawal. In contrast, the response to heat pain in both SI and SII was characterized by a double-peaked time course in which the maximum response (the 2nd peak) was consistently observed approximately 17 s after the onset of the stimulus (8 s following termination of the stimulus). This prolonged period of activation paralleled the perception of increasing pain intensity that persists even after stimulus offset. On the other hand, the temporal profile of the initial minor peak in pain-related activation closely matched that of the brush-evoked activity, suggesting a possible relationship to tactile components of the thermal stimulation procedure. These data indicate that both SI and SII cortices are involved in the processing of nociceptive information and are consistent with a role for these structures in the perception of temporal aspects of pain intensity.
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PMID:Differentiating noxious- and innocuous-related activation of human somatosensory cortices using temporal analysis of fMRI. 1209 68

The influence of attention on the processing of pain in the secondary somatosensory cortex (SII) was analyzed using magnetoencephalography in response to painful infra-red heat stimuli applied to the left hand in six male healthy subjects, aged 22-28 years. Three experimental paradigms were chosen to deliver attention dependent results under comparable levels of vigilance. Single moving dipole sources for the pain-evoked responses were calculated in the individual cortex anatomy determined by magnetic resonance imaging. Though pain stimuli followed the same intensity pattern in all paradigms, evoked SII activity increased markedly from the low attention task to the mid-level attention task (P < 0.001). In contrast, further increase of attention from mid-level to high was not accompanied by an additional enhancement of SII activity. It therefore is concluded that activation patterns of SII follow a saturation function which cannot be enlarged by maximizing the relevance of the painful stimuli.
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PMID:Attentional modulation of human pain processing in the secondary somatosensory cortex: a magnetoencephalographic study. 1212 52

Alterations in tactile sensitivity are common in patients with chronic pain. Recent brain imaging studies have indicated that brain areas activated by acute experimental pain partly overlap with areas processing innocuous tactile stimuli. However, the possible effect of chronic pain on central tactile processing has remained unclear. We have examined, both clinically and with whole-head magnetoencephalography, six patients suffering from complex regional pain syndrome (CRPS) of the upper limb. The cortical somatosensory responses were elicited by tactile stimuli applied to the fingertips and the reactivity of spontaneous brain oscillations was monitored as well. Tactile stimulation of the index finger elicited an initial activation at 65 ms in the contralateral SI cortex, followed by activation of the ipsi- and contralateral SII cortices at about 130 ms. The SI responses were 25-55% stronger to stimulation of the painful than the healthy side. The distance between SI representations of thumb and little finger was significantly shorter in the hemisphere contralateral than ipsilateral to the painful upper limb. In addition, reactivity of the 20-Hz motor cortex rhythm to tactile stimuli was altered in the CRPS patients, suggesting modified inhibition of the motor cortex. These results imply that chronic pain may alter central tactile and motor processing.
Pain 2002 Aug
PMID:Altered central sensorimotor processing in patients with complex regional pain syndrome. 1212 33

Cerebral processing of first pain, associated with A delta-fibers, has been studied intensively, but the cerebral processing associated with unmyelinated C-fibers, relating to second pain, remains to be investigated. This is the first study to clarify the primary cortical processing of second pain by magnetoencephalography, through the selective activation of C-fibers, by the stimulation of a tiny area of skin with a CO2 laser. In the hemisphere contralateral to the side stimulated, a one-source generator in the upper bank of the Sylvian fissure (secondary somatosensory cortex, SII) or two-source generators in SII and the hand area of the primary somatosensory cortex (SI) were the optimal configurations for the first component 1M. The onset and peak latency of the two sources in SI and SII were not significantly different. In the hemisphere ipsilateral to the stimulation, only one source was estimated in SII, and its peak latency was significantly (approximately 18 ms on average) longer than that of the SII source in the contralateral hemisphere. From our findings we suggest that parallel activation of SI and SII contralateral to the stimulation represents the first step in the cortical processing of C-fiber-related activities, probably related to second pain.
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PMID:Cerebral activation by the signals ascending through unmyelinated C-fibers in humans: a magnetoencephalographic study. 1212 94

There are a number of well-known stimulation methods for the investigation of the central projection of the vestibular system. In addition to optokinetic, galvanic and neck vibration tests, the most widespread method is caloric stimulation. These listed methods cause not only vestibular, but also other effects on the central nervous system (CNS) (acoustic, tactile and nociceptive). In this paper, positron emission tomography (PET) was used to investigate whether caloric stimulation contains a non-vestibular (extravestibular) component, which would cause a distortion in the cortical activity and therefore in the vestibular effect on the CNS. Caloric stimulation was carried out in six patients who had been operated on due to cerebello-pontine angle tumour. These patients suffered post-operatively from a complete lesion of the vestibular system and anacusis on the operated side. Ipsilaterally activated areas were the inferior pole of the post-central gyrus and temporoparietal junction, caudal part of the post-central gyrus (SI, SII), inferior parietal lobule and medial frontal gyrus. Contralaterally activated areas were the anterior cingulate gyrus, medial frontal gyrus, posterior part of the insula, post-central gyrus and temporoparietal junction (SII). Ipsilaterally deactivated areas were the caudal and cranial part of the medial occipital gyrus (V2, V3, V4, V5). Contralaterally deactivated areas were the lingual gyrus, inferior occipital gyrus (V2, V3) and fusiform gyrus. On the basis of these data, it was postulated that, during caloric stimulation, extravestibular reaction also occurs, which corresponds to the subjective feeling of heat and pain. The deactivation of the occipital cortex due to an extravestibular effect was demonstrated. This is the first observation to suggest the possibility of nociceptivevisual interaction.
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PMID:Changes in brain activation caused by caloric stimulation in the case of cochleovestibular denervation--PET study. 1235 95

Insular and SII cortices have been consistently shown by PET, fMRI, EPs, and MEG techniques to be activated bilaterally by a nociceptive stimulation. The aim of the present study was to refer to, and to compare within a common stereotactic space, the nociceptive responses obtained in humans by (i) PET, (ii) fMRI, (iii) dipole modeling of scalp LEPs, and (iv) intracerebral recordings of LEPs. PET, fMRI, and scalp LEPs were obtained from normal subjects during thermal pain. Operculoinsular LEPs were obtained from 13 patients using deep brain electrodes implanted for presurgical evaluation of drug-resistant epilepsy. Whatever the technique, we obtained responses which were located bilaterally in the insular and SII cortices. In electrophysiological responses (LEPs) the SII insular contribution peaked between 150 and 250 ms poststimulus and corresponded to the earliest portions of the whole cerebral response. Group analysis of PET and fMRI data showed highly consistent responses contralateral to stimulation. On single-subject analysis, LEPs and fMRI activations were concentrated in relatively restricted volumes even though spatial sampling was quite different for both techniques. Despite our multimodal approach, however, it was not possible to separate insular from SII activities. Individual variations in the anatomy and function of SII and insular cortices may explain this limitation. This multimodal study provides, however, cross-validated spatial and temporal information on the pain-related processes occurring in the operculoinsular region, which thus appears as a major site for the early cortical pain encoding in the human brain.
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PMID:Role of operculoinsular cortices in human pain processing: converging evidence from PET, fMRI, dipole modeling, and intracerebral recordings of evoked potentials. 1241 73

Clinical findings and recent non-invasive functional imaging studies pinpoint the insular cortex as the crucial brain area involved in cold sensation. By contrast, the role of primary (SI) and secondary (SII) somatosensory cortices in central processing of cold is controversial. So far, temporal activation patterns of cortical areas involved in cold processing have not been examined. Using magnetoencephalography, we studied, in seven healthy subjects, the temporo-spatial dynamics of brain processes evoked by innocuous and noxious cold stimulation as compared to tactile stimuli. For this purpose, a newly designed and magnetically silent cold-stimulator was employed. In separate runs, cold and painful cold stimuli were delivered to the dorsum of the right hand. Tactile afferents were stimulated by pneumatic tactile stimulation.Following innocuous cold stimulation (DeltaT=5+/-0.3 degrees C in 50+/-2ms), magnetic source imaging revealed an exclusive activation of the contra- and ipsilateral posterior insular cortex. The mean peak latencies were 194.3+/-38.1 and 241.0+/-31.7ms for the response in the ipsi- and contralateral insular cortex, respectively. Based on the measurement of onset latencies, the estimated conduction velocity of peripheral nerve fibres mediating cold fell in the range of Adelta-fibres (7.4+/-0.8 m/s). Noxious cold stimulation (DeltaT=35+/-5 degrees C in 70+/-12ms) initially activated the contra- and ipsilateral insular cortices in the same latency ranges as innocuous cold stimuli. Additionally, we found an activation of the contra- and ipsilateral SII areas (peak latencies 304+/-22.7 and 310.1+/-19.4ms, respectively) and a variable activation of the cingulate cortex. Notably, neither cold- nor painful cold stimulation produced an activation of SI. By contrast, the evoked cortical responses following tactile stimulation could be located to the contralateral SI cortex and bilateral SII. In conclusion, this study strongly corroborates the posterior insular cortex as the primary somatosensory area for cortical processing of cold sensation. Furthermore, it supports the role of SII and the cingulate cortex in mediating freeze-pain. Therefore, these results suggest different processing of cold, freeze-pain and touch in the human brain.
Pain 2002 Dec
PMID:Temporo-spatial analysis of cortical activation by phasic innocuous and noxious cold stimuli--a magnetoencephalographic study. 1246 99

The cortical areas that represent affectively positive and negative aspects of touch were investigated using functional magnetic resonance imaging (fMRI) by comparing activations produced by pleasant touch, painful touch produced by a stylus, and neutral touch, to the left hand. It was found that regions of the orbitofrontal cortex were activated more by pleasant touch and by painful stimuli than by neutral touch and that different areas of the orbitofrontal cortex were activated by the pleasant and painful touches. The orbitofrontal cortex activation was related to the affective aspects of the touch, in that the somatosensory cortex (SI) was less activated by the pleasant and painful stimuli than by the neutral stimuli. This dissociation was highly significant for both the pleasant touch (P < 0.006) and for the painful stimulus (P < 0.02). Further, it was found that a rostral part of the anterior cingulate cortex was activated by the pleasant stimulus and that a more posterior and dorsal part was activated by the painful stimulus. Regions of the somatosensory cortex, including SI and part of SII in the mid-insula, were activated more by the neutral touch than by the pleasant and painful stimuli. Part of the posterior insula was activated only in the pain condition and different parts of the brainstem, including the central grey, were activated in the pain, pleasant and neutral touch conditions. The results provide evidence that different areas of the human orbitofrontal cortex are involved in representing both pleasant touch and pain, and that dissociable parts of the cingulate cortex are involved in representing pleasant touch and pain.
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PMID:Representations of pleasant and painful touch in the human orbitofrontal and cingulate cortices. 1257 Nov 20

There are two kinds of pain, a sharp pain ascending through Adelta fibers (first pain) and a second burning pain ascending though C fibers (second pain). By using a novel method, the application of a low intensity CO(2) laser beam to a tiny area of skin using a very thin aluminum plate with numerous tiny holes as a spatial filter, we succeeded in selectively stimulating unmyelinated C fibers of the skin in humans, and could record consistent and clear brain responses using electroencephalography (EEG) and magnetoencephalography (MEG). The conduction velocity (CV) of the C fibers of the peripheral nerve and spinal cord, probably spinothalamic tract (STT), is approximately 1-4 m/s, which is significantly slower than that of Adelta (approximately 10-15 m/s) and Abeta fibers (approximately 50-70 m/s). This method should be very useful for clinical application. Following C fiber stimulation, primary and secondary somatosensory cortices (SI and SII) are simultaneously activated in the cerebral hemisphere contralateral to the stimulation, and then, SII in the hemisphere ipsilateral to the stimulation is activated. These early responses are easily detected by MEG. Then, probably limbic systems such as insula and cingulate cortex are activated, and those activities reflected in EEG components. Investigations of the cortical processing in pain perception including both first and second pain should provide a better understanding of pain perception and, therefore, contribute to pain relief in clinical medicine.
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PMID:Cerebral responses following stimulation of unmyelinated C-fibers in humans: electro- and magneto-encephalographic study. 1263 62


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