英国研究人员日前报告说已探清了迷幻蘑菇导致幻觉的原因，即迷幻蘑菇含有的一种物质会导致大脑某些部位的活动性减弱，这项发现或许有助治疗抑郁症等精神疾病。
英国帝国理工学院等机构研究人员在新一期美国《国家科学院学报》上报告说，迷幻蘑菇中含有的致幻物质是“二甲-4-羟色胺磷酸”，研究人员为一些健康志愿者注射了这种物质，同时利用磁共振成像技术对他们大脑进行扫描，观察大脑中出现的变化。
结果发现，与以前人们猜测这种物质致幻是因为增加了大脑的活动性不同，它减弱了大脑中一些部位的活动性，如内侧前额叶皮层、后带皮层等。这些部位在大脑中起着“连接中枢”的作用，能够协调各个功能部位的感受，研究人员因此认为，这些“连接中枢”活动性的降低，导致了大脑各个功能部位之间信息互相传递的脱节，从而引起各种奇怪的幻觉。
研究人员罗宾·卡哈特-哈里斯说，这项发现还说明或许可以用从迷幻蘑菇中提取出的物质来帮助治疗抑郁症。过去曾有研究发现，许多抑郁症患者大脑中的相关部位活动性过高，也有一些医生基于经验而使用迷幻蘑菇来帮助治疗抑郁症，但其背后的科学原理一直不太清楚，本次研究结果为此提供了支持，说明迷幻蘑菇的药用价值值得进一步研究。(生物谷 Bioon.com)
doi:10.1073/pnas.1119598109
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Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin
Robin L. Carhart-Harris, David Erritzoe, Tim Williams, James M. Stone, Laurence J. Reed, Alessandro Colasanti, Robin J. Tyacke, Robert Leech, Andrea L. Malizia, Kevin Murphy, Peter Hobden, John Evans, Amanda Feilding, Richard G. Wise, and David J. Nutt
Psychedelic drugs have a long history of use in healing ceremonies, but despite renewed interest in their therapeutic potential, we continue to know very little about how they work in the brain. Here we used psilocybin, a classic psychedelic found in magic mushrooms, and a task-free functional MRI (fMRI) protocol designed to capture the transition from normal waking consciousness to the psychedelic state. Arterial spin labeling perfusion and blood-oxygen level-dependent (BOLD) fMRI were used to map cerebral blood flow and changes in venous oxygenation before and after intravenous infusions of placebo and psilocybin. Fifteen healthy volunteers were scanned with arterial spin labeling and a separate 15 with BOLD. As predicted, profound changes in consciousness were observed after psilocybin, but surprisingly, only decreases in cerebral blood flow and BOLD signal were seen, and these were maximal in hub regions, such as the thalamus and anterior and posterior cingulate cortex (ACC and PCC). Decreased activity in the ACC/medial prefrontal cortex (mPFC) was a consistent finding and the magnitude of this decrease predicted the intensity of the subjective effects. Based on these results, a seed-based pharmaco-physiological interaction/functional connectivity analysis was performed using a medial prefrontal seed. Psilocybin caused a significant decrease in the positive coupling between the mPFC and PCC. These results strongly imply that the subjective effects of psychedelic drugs are caused by decreased activity and connectivity in the brain's key connector hubs, enabling a state of unconstrained cognition.
