Current biology : CB
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Reduced pain perception while being distracted from pain is an everyday example of how cognitive processes can interfere with pain perception. Previous neuroimaging studies showed distraction-related modulations of pain-driven activations in various cortical and subcortical brain regions, but the precise neuronal mechanism underlying this phenomenon is unclear. Using high-resolution functional magnetic resonance imaging of the human cervical spinal cord in combination with thermal pain stimulation and a well-established working memory task, we demonstrate that this phenomenon relies on an inhibition of incoming pain signals in the spinal cord. ⋯ At the individual level, reductions of neuronal responses in the spinal cord predicted behavioral pain reductions. In a subsequent behavioral experiment, using the opioid antagonist naloxone in a double-blind crossover design with the same paradigm, we demonstrate a substantial contribution of endogenous opioids to this mechanism. Taken together, our results show that the reduced pain experience during mental distraction is related to a spinal process and involves opioid neurotransmission.
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With unrest in oil-exporting countries, backlashes against biofuels and photovoltaics, and a nuclear incident in Japan, the year 2011 rattled confidence in future energy supplies. The search for alternatives is all the more urgent, but some of the solutions investigated hark back to fossil fuels that we can't afford to burn.
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Current biology : CB · Dec 2011
Cortical hypersynchrony predicts breakdown of sensory processing during loss of consciousness.
Intrinsic cortical dynamics modulates the processing of sensory information and therefore may be critical for conscious perception. We tested this hypothesis by electroencephalographic recording of ongoing and stimulus-related brain activity during stepwise drug-induced loss of consciousness in healthy human volunteers. We found that progressive loss of consciousness was tightly linked to the emergence of a hypersynchronous cortical state in the alpha frequency range (8-14 Hz). ⋯ The antagonistic relation between the late sensory response and ongoing alpha activity held for constant drug levels on the single-trial level. Specifically, the late response component was negatively correlated with the power and long-range coherence of ongoing frontal alpha activity. Our results suggest blocking of intracortical communication by hypersynchronous ongoing activity as a key mechanism for the loss of consciousness.