单选题 Scientists researching hypnosis have uncovered evidence that counters some of the skepticism about the technique. One skeptical hypothesis is that hypnosis may be the product of "vivid imagination", a now discredited charge stemming from the observation that many people who are hypnotizable can be led to experience compellingly realistic auditory and visual hallucinations. Nothing that an auditory hallucination and the act of imagining a sound are both self-generated and that, like real hearing, a hallucination is experienced as the product of an external source, Henry Szechtman used PET(positron emission tomography)to image the brain activity of hypnotized subjects invited to imagine a scenario and then experiencing a hallucination. By monitoring regional blood flow in areas activated during both hearing and auditory hallucination but not during simple imagining, the investigators sought to determine where in the brain a hallucinated sound is mistakenly "tagged" as authentic and originating in the outside world. Szechtman imaged the brain activity of eight very hypnotizable subjects who had been prescreened for their ability to hallucinate under hypnosis. During the session, the subjects were under hypnosis and lay in the PET scanner with their brain activity being monitored under four conditions: at rest;while hearing an audiotape of a voice, while imagining hearing the voice again;and during the auditory hallucination they experienced after being informed that the tape was playing once more, although it was not. The tests suggested that a region of the brain called the right anterior cingulate cortex was just as active while the volunteers were hallucinating as it was while they were actually hearing the stimulus. In contrast, that brain area remained dormant while the subjects were imagining that they heard the stimulus. The second major objection raised by critics argues that hypnosis' ability to blunt pain results from either simple relaxation or a placebo response. McGlashan established that while hypnosis was only as effective in reducing pain as a sugar pill for poorly hypnotizable people, highly hypnotizable subjects benefited three times more from hypnosis than from the placebo. In response to these successes, Rainville devised experiments to determine which brain structures are involved in pain relief during hypnosis, attempting to locate the brain structures associated with the suffering component of pain, as distinct from its sensory aspects. Using PET, he and other scientists found that hypnosis reduced the activity of the anterior cingulate cortex—an area known to be involved in pain—but did not affect the activity of the somatosensory cortex, where the sensations of pain are processed. Despite the value of these findings, the mechanisms underlying hypnotic pain relief are still poorly understood. The model favored by most researchers is that the analgesic effect of hypnosis occurs in higher brain centers than those involved in registering the painful sensation, accounting for the fact that most autonomic responses that routinely accompany pain—such as increased heart rate — are relatively unaffected by hypnotic suggestions of analgesia.

单选题 According to the passage, which of the following is one of the primary factors that led researchers studying hypnosis to compare auditory hallucinations and imagined sounds?

单选题 It can be inferred that researchers abandoned the skeptical "vivid imagination" hypothesis because

单选题 Which of the following best expresses the main idea of the passage?

单选题 The research described in the passage is primarily concerned with answering which of the following questions?

单选题 Which of the following best defines "higher brain centers" as the term is used in the passage?

单选题 Which of the following best describes the organization of the argument that the author of the passage presents in the last two paragraphs?