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Learning under the knife

Learning under the knife

作者:微生凫的  时间:2019-03-07 02:04:00  人气:

By Laura Spinney EVEN surgical patients who are adequately anaesthetised may have unconscious memories from their time in the operating theatre. Researchers in Sheffield stumbled on this discovery while testing people’s ability to learn words under sedation—and they believe the physical trauma caused by the surgeon’s knife is the trigger. Three in every thousand patients remember something about their operation when they come round from a general anaesthetic, such as a remark from the surgeon. And many more retain some implicit memory of events in the operating theatre that may affect their subsequent behaviour, even if they are not aware of it. To avoid the distress that these memories may cause, psychologists and anaesthetists are trying to find out how they form. Can we learn while deeply unconscious, or have those who remember something from surgery woken up fleetingly? Jackie Andrade, a psychologist at the University of Sheffield, and her colleagues tested people’s memory for words spoken to them while lightly sedated with propofol, a widely used anaesthetic. Even though the volunteers remained conscious and could answer to their names, they were unable to remember the words afterwards. They did not even have implicit memories of them, as shown by their inability to reproduce the words in a free-association task. This was puzzling, because the amount of propofol administered was much less than that given to surgical patients. So the researchers wondered if pre-operative anxiety might increase the likelihood of a patient remembering. However, when they played the words to sedated patients prior to surgery they still found no evidence of learning. Next, Andrade and her colleague Clare Stapleton, an anaesthetist at the University of Bristol, played the words to 72 women undergoing surgery to harvest their eggs for IVF. The women were not anxious about the surgery. And even though they had received up to three times as much propofol as the patients in the previous experiment, the verbal test showed that they had some significant memory for the words. When asked if they remembered hearing them, however, they denied it. Some aspect of surgery may aid the formation of unconscious memories, suggests Andrade. “I’m interested in adrenaline because it’s known to be connected to memory function,” she says. The amount of adrenaline released in response to pre-operative anxiety may be insufficient, but the surge triggered by tissue damage could induce learning. But Michael Wang of the University of Hull, who has claimed that almost half of all patients are awake during surgery, remains unconvinced. The cognitive arousal that is known to be associated with surgery could be bringing patients closer to the threshold of consciousness where normal learning occurs. “It’s highly likely that patients have had episodes of wakefulness,