2 . People with a rare genetic disorder known as Prader-Willi syndrome never feel full, and this excess hunger can lead to life-threatening obesity (肥胖症). Scientists studying the problem have now found that the fist-shaped structure known as the cerebellum (小脑) — which had not previously been linked to hunger — is key to regulating satiation (饱食) in those with this condition.

This finding is the latest in a series of discoveries revealing that the cerebellum, long thought to be primarily involved in movement harmony, also plays a broad role in cognition, emotion and behavior. “We’ve opened up a whole field of cerebellar control of food intake,” says Albert Chen, a neuroscientist at the Scintillon Institute in California.

The project began with an accidental observation: Chen and his team noticed they could make mice stop eating by activating small pockets of neurons (神经元) in regions known as the anterior deep cerebellar nuclei (aDCN), within the cerebellum. Fascinated, the researchers gathered data using functional MRI to compare brain activity in 14 people who had Prader-Willi syndrome with activity in 14 unaffected people while each testee viewed images of food -- either immediately following a meal or after fasting (禁食) for at least four hours.

New analysis of these scans revealed that activity in the same regions Chen’s group had accurately pointed out in mice, the aDCN, appeared to be significantly disturbed in humans with Prader-Willi syndrome. In healthy individuals, the aDCN were more active in response to food images while fasting than just after a meal, but no such difference was identifiable in participants with the disorder. The result suggested that the aDCN were involved in controlling hunger. Further experiments on mice, conducted by researchers from several different institutions, demonstrated that activating the animals’ aDCN neurons dramatically reduced food intake by weakening how the brain’s pleasure center responds to food.

For years neuroscientists studying appetite focused mainly either on the hypothalamus, a brain area involved in regulating energy balance, or on reward-processing centers such as the nucleus accumbens (伏隔核). But this group has identified a new feeding center in the brain, says Elanor Hinton, a neuroscientist at the University of Bristol in England who was not involved with the study. “I’ve been working in appetite research for the past 15 years or so, and the cerebellum has just not been a target,” Hinton says. “I think this is going to be important both for Prader-Willi syndrome and, much more widely, to address obesity in the general population.”

5 . “A writer’s job is to tell the truth,” said Hemingway in 1942. No other writer of our time had so fiercely stated, or so consistently (一贯地) illustrated the writer’s duty to speak truly. His standard of truth-telling remained, moreover, so high and so strict that he was ordinarily unwilling to admit secondary evidence, whether literary evidence or evidence picked up from other sources than his own experience. “I only know what I have seen”, was a statement which came often to his lips and pen. What he had personally done, or what he knew unforgettably by having gone through one version of it, was what he was interested in telling about.

The primary intention of his writing, from first to last, was to seize and project for the reader what he often called “the way it was”. This is a characteristically simple phrase for a concept of extraordinary complexity, and Hemingway’s concept of its meaning subtly (微妙地) changed several times in the course of his career - always in the direction of greater complexity. At the core of the concept, however, one can invariably recognize the operation of three instruments of beauty appreciation: the sense of place, the sense of fact, and the sense of scene.

The first of these, obviously a strong passion with Hemingway, is the sense of place. “Unless you have geography, background,” he once told George Antheil, “you have nothing.” You have, that is to say, a dramatic vacuum. Few writers have been more place-conscious. Few have so carefully charted out the geographical ground work of their novels while managing to keep background so unnoticeable. Few, accordingly, have been able to record more economically and graphically the way it is when you watch the bulls running through the streets of Pamplona, Spain towards the bull-ring.

“When I woke it was the sound of the rocket exploding that announced the release of the bulls. Down below the narrow street was empty. All the balconies were crowded with people. Suddenly a crowd came down the street. They were all running, packed close together. They passed along and up the street toward the bull-ring and behind them came more men running faster, and then some stragglers (落后者) who were really running. Behind them was a little bare space, and then the bulls tossing their heads up and down. It all went out of sight around the corner. One man fell, rolled to the gutter (排水沟), and lay quiet. But the bulls went right on and did not notice him. They were all running together.”