NeuroImage
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Randomized Controlled Trial Clinical Trial
Expectancy and belief modulate the neuronal substrates of pain treated by acupuncture.
Both specific and non-specific factors may play a role in acupuncture therapy for pain. We explored the cerebral consequences of needling and expectation with real acupuncture, placebo acupuncture and skin-prick, using a single-blind, randomized crossover design with 14 patients suffering from painful osteoarthritis, who were scanned with positron emission tomography (PET). ⋯ Real acupuncture and placebo (with the same expectation of effect as real acupuncture) caused greater activation than skin prick (no expectation of a therapeutic effect) in the right dorsolateral prefrontal cortex, anterior cingulate cortex, and midbrain. These results suggest that real acupuncture has a specific physiological effect and that patients' expectation and belief regarding a potentially beneficial treatment modulate activity in component areas of the reward system.
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To study the spatial and behavioral dynamics of cortical sources for N20m and P35m at varying stimulus intensities, we measured neuromagnetic cortical responses to left electric median nerve stimulation at the wrist in 17 male healthy adults. The stimulus intensity levels were individually determined according to sensory threshold (ST) for perceiving electric pulses. Using equivalent current dipole (ECD) modeling, we analyzed the peak latencies, amplitudes, and locations of ECDs from 14 subjects for N20m and P35m elicited at 2 ST, 3 ST, and 4 ST. ⋯ Superimposed over subjects' own MR images, N20m ECDs were localized in the area of 3b contralateral to stimulus side in all 17 subjects at 3 ST, whereas P35m ECDs were localized either in the postcentral (in 14 subjects) or in the precentral areas (in 3 subjects). We found no clear correlation between N20m and P35m in terms of peak latencies as well as the corresponding growth of activation strengths along with stepwise increase in stimulus intensity. Our results imply that the two early SEF components, N20m and P35m, have differential cortical generators, with distinctive neurophysiological behaviors in response to varying stimulus intensity levels.
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The objective of the present study was to assess the spatiotemporal scenario of brain activity associated with sensory stimulation of the abductor pollicis brevis muscle. Spatiotemporal dipole models, using realistic individual boundary element head models, were built from somatosensory evoked potentials (SEPs; 64 Ch. EEG) to nonpainful and painful intramuscular electrostimulation (IMES) as well as to cutaneous electrostimulation delivered to the distal phalanx of the thumb. ⋯ This source was unmasked by the lower stimulus intensity; (4) a source for IMES was located in the contralateral caudal CMA rather than being located in the cingulate gyrus. Cerebral sensory processing of input from the muscle involved several sensory and motor areas and likely occurs in two parallel streams subserving higher order somatosensory processing as well as sensory-motor integration. The two streams might on one hand involve sensory discrimination via SI and SII and on the other hand integration of sensory feedback for further motor processing via MI, lateral PM area, and caudal CMA.
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Functional magnetic resonance imaging (fMRI) was used to investigate the effects of inspired hypoxic, hyperoxic, and hypercapnic gases on baseline and stimulus-evoked changes in blood oxygenation level-dependent (BOLD) signals, cerebral blood flow (CBF), and the cerebral metabolic rate of oxygen (CMRO2) in spontaneously breathing rats under isoflurane anesthesia. Each animal was subjected to a baseline period of six inspired gas conditions (9% O2, 12% O2, 21% O2, 100% O2, 5% CO2, and 10% CO2) followed by a superimposed period of forepaw stimulation. Significant stimulus-evoked fMRI responses were found in the primary somatosensory cortices. ⋯ However, under 9% O2 and 10% CO2, stimulus-evoked CBF and BOLD were substantially reduced and the CMRO2 formalism appeared invalid, likely due to attenuated neurovascular coupling and/or a failure of the model under extreme physiological perturbations. These findings demonstrate that absolute fMRI measurements help distinguish neural from non-neural contributions to the fMRI signals and may lend a more accurate measure of brain activity during states of altered basal physiology. Moreover, since numerous pharmacologic agents, pathophysiological states, and psychiatric conditions alter baseline physiology independent of neural activity, these results have implications for neuroimaging studies using relative fMRI changes to map brain activity.
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Independent component analysis (ICA) is a data-driven approach utilizing high-order statistical moments to find maximally independent sources that has found fruitful application in functional magnetic resonance imaging (fMRI). Being a blind source separation technique, ICA does not require any explicit constraints upon the fMRI time courses. However, for some fMRI data analysis applications, such as for the analysis of an event-related paradigm, it would be useful to flexibly incorporate paradigm information into the ICA analysis. ⋯ Compared with a traditional GLM approach, the sbICA approach provides a flexible way to analyze fMRI data that reduces the assumptions placed upon the hemodynamic response of the brain. The advantages and limitations of our technique are discussed in detail in the manuscript to provide guidelines to the reader for developing useful applications. The use of prior time course information in a spatial ICA analysis, which combines elements of both a regression approach and a blind ICA approach, may prove to be a useful tool for fMRI analysis.