Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale
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Cyclic vomiting syndrome (CVS) is a chronic disorder characterized by episodic nausea and vomiting. A large proportion of patients use marijuana to control their symptoms. Several case reports implicate marijuana as a cause of intractable vomiting with compulsive hot water bathing considered pathognomonic of "cannabinoid hyperemesis." We sought to examine the relationship between marijuana use and CVS. ⋯ With marijuana use, patients noted the greatest improvement with stress levels, appetite and nausea. Marijuana users were more likely to be male and have associated anxiety. Hot showers were not pathognomonic of marijuana use though they were more likely to be associated with its use.
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Nausea is a noxious, uncomfortable feeling usually located in the epigastrium. The pathophysiology of nausea encompasses brain-gut and gut-brain interaction. Nausea is associated with myoelectrical dysrhythmias of the stomach, an objective marker in the periphery. The aims of this review were to describe (1) the physiology of normal 3 cycle per minute (cpm) gastric myoelectrical activity and (2) conditions where shifts from normal 3 cpm gastric rhythms to gastric dysrhythmias are associated with the onset of nausea. Illusory self-motion, infusion of drugs such as morphine and glucagon, and ingestion of water or nutrient loads are several of the multitude of stimuli that induce acute nausea and a variety of gastric dysrhythmias such as tachygastrias (3.75-10 cpm) and bradygastrias (1.0-2.5 cpm). In nausea of motion sickness, increased nausea severity correlates with increased plasma vasopressin and epinephrine levels. Gastric dysrhythmias are also present in chronic gastrointestinal neuromuscular disorders such as gastroparesis. When gastric dysrhythmias resolve after drug or device therapies, nausea resolves. The shift in state from comfort in the epigastrium area and normal 3 cpm gastric rhythm to symptoms of nausea and gastric dysrhythmias represents dynamic gut-brain and brain-gut interactions that can be tracked by changes in gastric rhythm. ⋯ (1) gastric dysrhythmias represent at least one peripheral mechanism underlying the symptom of nausea, and (2) gastric dysrhythmias are an objective biomarker for nausea and potential therapeutic targets for anti-nauseant therapies.
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Past studies, using pairings of auditory tones and visual flashes, which were static and coincident in space but variable in time, demonstrated errors in judging the temporal patterning of the visual flashes-the sound-induced flash illusion. These errors took one of the two forms: under-reporting (sound-induced fusion) or over-reporting (sound-induced fission) of the flash numbers. Our study had three objectives: to examine the robustness of both illusions and to consider the effects of stimulus set and response bias. ⋯ Conversely, sound-induced fission was the most likely outcome for the flash-tone pairing which contained two flashes. Fission was also shown to be strongly driven by stimuli confounds such as categorical boundary conditions (e.g. flash-tone pairings with ≤2 flashes) and compressed response options. These findings suggest whilst both fission and fusion are associated with 'auditory driving', the differences in the occurrence and strength of the two illusions not only reflect the separate neuronal mechanisms underlying audio and visual signal processing, but also the test conditions that have been used to investigate the sound-induced flash illusion.
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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.