Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Randomized Controlled Trial
The effect of transcranial direct current stimulation on experimentally induced heat pain.
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique that can affect human pain perception. Placebo effects are present in most treatments and could therefore also interact with treatment effects in tDCS. The present study investigated whether short-term tDCS reduced heat pain intensity, stress, blood pressure and increased heat pain thresholds in healthy volunteers when controlling for placebo effects. ⋯ The results revealed no effects on pain thresholds. There was a tendency that active tDCS reduced stress and systolic blood pressure, however, not significant. In sum, tDCS had an analgesic effect on high-intensity pain, but the effect of tDCS could not be separated from placebo effects for medium and low pain.
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Randomized Controlled Trial
Novelty detection is enhanced when attention is otherwise engaged: an event-related potential study.
Novel stimuli are detected and evaluated quickly, suggesting that processing them is a priority for the brain. In the present study, the effects of attention on this early visual novelty processing were investigated in two experiments using the event-related potential (ERP) technique. In the first experiment, participants performed two tasks that varied in the amount of attention available for novel stimuli. ⋯ In a second experiment, a condition was added in which working memory load was low, but visual oddball stimuli were task-irrelevant. Results from this experiment showed that while the reduction in P3a amplitude was due to task irrelevance, the enhanced anterior N2 was linked to a high working memory load. This suggests that novelty detection is enhanced when attention is otherwise engaged.
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Randomized Controlled Trial
Audiotactile interactions beyond the space and body parts around the head.
Recent research has reported that spatial modulation effects of audiotactile interactions tend to be limited to the space and body parts around the head. The present study investigated the generality of this finding by manipulating body parts stimulated and spatial relationships between the body parts and sounds. In Experiment 1, tactile stimuli were presented randomly to either left or right cheek, hand (palm or back) placed near the head, and knee while auditory stimuli were presented to either the same or opposite side from loudspeakers close to the head. ⋯ The sounds delivered from near the head exerted a greater influence on tactile spatial discrimination performance as compared with the sound delivered from far from the head. Furthermore, the back of the hand was more influenced by the auditory stimuli than the palm when the hands were placed near the sounds. These results suggest that the spatial modulation effects of audiotactile interactions can occur beyond the space and body surface around the head.
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Randomized Controlled Trial
Psychophysical testing of spatial and temporal dimensions of endogenous analgesia: conditioned pain modulation and offset analgesia.
The endogenous analgesia (EA) system is psychophysically evaluated using various paradigms, including conditioned pain modulation (CPM) and offset analgesia (OA) testing, respectively, the spatial and temporal filtering processes of noxious information. Though both paradigms assess the function of the EA system, it is still unknown whether they reflect the same aspects of EA and consequently whether they provide additive or equivalent data. Twenty-nine healthy volunteers (15 males) underwent 5 trials of different stimulation conditions in random order including: (1) the classic OA three-temperature stimulus train ('OA'); (2) a three-temperature stimulus train as control for the OA ('OAcon'); (3) a constant temperature stimulus ('constant'); (4) the classic parallel CPM ('CPM'); and (5) a combination of OA and CPM ('OA + CPM'). ⋯ Furthermore, a correlation was found between OA and CPM (r = 0.62, P = 0.01) at the time of maximum OA effect. The additive effect found suggests that the two paradigms represent at least partially different aspects of EA. The moderate association between the CPM and OA magnitudes indicates, on the other hand, some commonality of their underlying mechanisms.
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Randomized Controlled Trial
A pharmaco-fMRI study on pain networks induced by electrical stimulation after sumatriptan injection.
Sumatriptan, a drug widely used to alleviate migraine headaches, has several somatosensory adverse effects, including tactile allodynia. To understand whether sumatriptan affects sensory and affective circuitries simultaneously, we investigated the responses of 12 healthy volunteers to electrical stimuli after infusion with either sumatriptan or saline. Using a double-blind crossover study design, we used functional magnetic resonance imaging (fMRI) to measure brain activation in different areas during electrical stimulation. ⋯ In contrast, activation following saline administration was observed primarily in the lateral pain system, including the primary sensory cortex, lateral SII, posterior insular cortex, anterior ACC, and lateral thalamus. Importantly, we found that VAS ratings and MPQ scores were increased after sumatriptan infusion, but not after saline administration. Our fMRI, VAS, and SF-MPQ findings suggest that sumatriptan plays a significant role in the affective dimension of pain and a minor role related to sensory discrimination.