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Searching for God in the Brain
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来源：网络文摘 作者：佚名 发布时间：2007-10-17
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When the Buddhist subjects reached their self-reported meditation peak, a state in which they lose their sense of existence as separate individuals, the researchers injected them with a radioactive isotope that is carried by the blood to active brain areas. The investigators then photographed the isotope’s distribution with a special camera—a technique called single-photon-emission computed tomography (SPECT).
The height of this meditative trance, as they described in a 2001 paper, was associated with both a large drop in activity in a portion of the parietal lobe, which encompasses the upper back of the brain, and an increase in activity in the right prefrontal cortex, which resides behind the forehead. Because the affected part of the parietal lobe normally aids with navigation and spatial orientation, the neuroscientists surmise that its abnormal silence during meditation underlies the perceived dissolution of physical boundaries and the feeling of being at one with the universe. The prefrontal cortex, on the other hand, is charged with attention and planning, among other cognitive duties, and its recruitment at the meditation peak may reflect the fact that such contemplation often requires that a person focus intensely on a thought or object. CHINAGEO中国地理网
Neuroscientist Richard J. Davidson of the University of Wisconsin–Madison and his colleagues documented something similar in 2002, when they used fMRI to scan the brains of several hundred meditating Buddhists from around the world. Functional MRI tracks the flow of oxygenated blood by virtue of its magnetic properties, which differ from those of oxygen-depleted blood. Because oxygenated blood preferentially flows to where it is in high demand, fMRI highlights the brain areas that are most active during—and thus presumably most engaged in—a particular task.
Davidson’s team also found that the Buddhists’ meditations coincided with activation in the left prefrontal cortex, again perhaps reflecting the ability of expert practitioners to focus despite distraction. The most experienced volunteers showed lower levels of activation than did those with less training, conceivably because practice makes the task easier. This theory jibes with reports from veterans of Buddhist meditation who claim to have reached a state of “effortless concentration,” Davidson says. chinageog.com
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What is more, Newberg and d’Aquili obtained concordant results in 2003, when they imaged the brains of Franciscan nuns as they prayed. In this case, the pattern was associated with a different spiritual phenomenon: a sense of closeness and mingling with God, as was similarly described by Beauregard’s nuns. “The more we study and compare the neurological underpinnings of different religious practices, the better we will understand these experiences,” Newberg says. “We would like to [extend our work by] recruiting individuals who engage in Islamic and Jewish prayer as well as revisiting other Buddhist and Christian practices.”
Newberg and his colleagues discovered yet another activity pattern when they scanned the brains of five women while they were speaking in tongues—a spontaneous expression of religious fervor in which people babble in an incomprehensible language. The researchers announced in 2006 that the activity in their subjects’ frontal lobes—the entire front section of the brain—declined relative to that of five religious people who were simply singing gospel. Because the frontal lobes are broadly used for self-control, the research team concluded that the decrement in activity there enabled the loss of control necessary for such garrulous outbursts. 来源：中国地理网
Spiritual Networking
Although release of frontal lobe control may be involved in the mystical experience, Beauregard believes such profound states also call on a wide range of other brain functions. To determine exactly what might underlie such phenomena, the Quebecois neuroscientist and his colleagues used fMRI to study the brains of 15 nuns during three different mental states. Two of the conditions—resting with closed eyes and recollecting an intense social experience—were control states against which they compared the third: reminiscence or revival of a vivid experience with God.
As each nun switched between these states on a technician’s cue, the MRI machine recorded cross sections of her brain every three seconds, capturing the whole brain roughly every two minutes. Once the neural activity was computed and recorded, the experimenters compared the activation patterns in the two control states with those in the religious state to elucidate the brain areas that became more energized during the mystical experience. (Although Beauregard had hoped the nuns would experience a mystical union while in the scanner, the best they could do, it turned out, was to conjure up an emotionally powerful memory of union with God. “God can’t be summoned at will,” explained Sister Diane, the prioress of the Carmelite convent in Montreal.) chinageog.com
The researchers found six regions that were invigorated only during the nuns’ recall of communion with God. The spiritual memory was accompanied by, for example, increased activity in the caudate nucleus, a small central brain region to which scientists have ascribed a role in learning, memory and, recently, falling in love; the neuroscientists surmise that its involvement may reflect the nuns’ reported feeling of unconditional love. Another hot spot was the insula, a prune-size chunk of tissue tucked within the brain’s outermost layers that monitors body sensations and governs social emotions. Neural sparks there could be related to the visceral pleasurable feelings associated with connections to the divine.
And augmented activity in the inferior parietal lobe, with its role in spatial awareness—paradoxically, the opposite of what Newberg and Davidson witnessed—might mirror the nuns’ feeling of being absorbed into something greater. Either too much or too little activity in this region could, in theory, result in such a phenomenon, some scientists surmise. The remainder of the highlighted regions, the researchers reported in the September 25, 2006, issue of Neuroscience Letters, includes the medial orbitofrontal cortex, which may weigh the pleasantness of an experience; the medial prefrontal cortex, which may help govern conscious awareness of an emotional state; and, finally, the middle of the temporal lobe. www.chinageo.com
The quantity and diversity of brain regions involved in the nuns’ religious experience point to the complexity of the phenomenon of spirituality. “There is no single God spot, localized uniquely in the temporal lobe of the human brain,” Beauregard concludes. “These states are mediated by a neural network that is well distributed throughout the brain.”
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Brain scans alone cannot fully describe a mystical state, however. Because fMRI depends on blood flow, which takes place on the order of seconds, fMRI images do not capture real-time changes in the firing of neurons, which occur within milliseconds. That is why Beauregard turned to a faster technique called quantitative electroencephalography (EEG), which measures the voltage from the summed responses of millions of neurons and can track its fluctuation in real time. His team outfitted the nuns with red bathing caps studded with electrodes that pick up electric currents from neurons. These currents merge and appear as brain waves of various frequencies that change as the nuns again recall an intense experience with another person and a deep connection with God. chinageog.com
Beauregard and his colleagues found that the most prevalent brain waves are long, slow alpha waves such as those produced by sleep, consistent with the nuns’ relaxed state. In work that has not yet been published, the scientists also spotted even lower-frequency waves in the prefrontal and parietal cortices and the temporal lobe that are associated with meditation and trance. “We see delta waves and theta waves in the same brain regions as the fMRI,” Beauregard says.
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