Every decision we make is arrived at through hugely complex neurological processing. Although it feels as though you have a choice, the action that you ‘decide’ to take is entirely directed by automatic neural activity. Brain imaging studies show that a person’s action can be predicted by their brain activity up to 10 seconds before they themselves become aware they are going to act. Multiple neuroscientific studies show that even those important decisions that feel worked out are just as automatic as knee-jerk reactions (膝跳反应) (although more complex).

Decision-making starts with the amygdala: a set of two almond-shaped nuclei (杏仁状核) buried deep within the brain, which generate emotion. The amygdala registers the information streaming in through our senses and responds to it in less than a second, sending signals throughout the brain. These produce an urge to run, fight, freeze or grab, according to how the amygdala values various stimuli.

Before we act on the amygdala’s signals, however, the information is usually processed by other brain areas, including some that produce conscious thoughts and emotions. Areas concerned with recognition work out what’s going on, those concerned with memory compare it with previous experiences, and those concerned with reasoning, judging and planning get to work on constructing various action plans. The best plan—if we are lucky—is then selected and carried out. If any of this process goes wrong, we are likely to hesitate, or do something silly.

The various stages of decision-making are marked by different types of brain activity. Fast (gamma)waves, with frequencies of 25 to 100 Hz, produce a keen awareness of the multiple factors that need to be taken into account to arrive at a decision. If you are trying to choose a sandwich, for instance, gamma waves generated in various cells within the ‘taste’ area of the brain bring to mind and compare the taste of ham, hummus, wholemeal, sourdough, and so on. Although it may seem useful to be aware of the full range of choice, too much information makes decision-making more difficult, so irrelevant factors get dismissed quickly and unconsciously.

After this comparison stage, the brain switches to slow-wave activity (12 to 30 Hz). This extinguishes most of the gamma activity, leaving just a single ‘hotspot’ of gamma waves which marks the chosen option.

Although there is no ‘you’ outside your brain to direct what it’s doing, you can help it to make good decisions by placing yourself in a situation which is likely to make the process run more smoothly. Doing something that is physically or mentally stimulating before making a decision will help your brain produce the initial gamma waves that generate awareness of the competing options. Getting over-excited, on the other hand, will prevent the switch to the slow brainwaves, making it much harder to single out a choice.

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.”

Picture an iceberg(冰山).You'll probably imagine something white as snow rising up out of a blue sea. But icebergs can be all sorts of shades. They can be from a frosty blue to an attractive green.

Researchers and sailors have observed emerald(翠绿色)icebergs for years. A large piece of ice "mast-high" and "green as emerald" even appears in Samuel Taylor Coleridge's 1834 poem. But they haven't found out exactly why these icebergs look the way they do.

A new paper led by Stephen Warren was published. It all has to do with what icebergs are made out of. Icebergs break off glaciers(冰川)or ice shelves, which happens mainly around Antarctica and Greenland. They begin their lives as snowfall that accumulates over time. So. icebergs contain air pockets with the form of bubbles that spread light. With some exceptions and rare lines, glacier ice tends to look bluish white.

At first，Warren guessed that the green was a product of melt carbon. And it came from rotting plants or sea animals. But samples(样本)didn't prove it. Another idea started to take shape after they had found a high concentration of iron in a sample of sea ice from the Amery Ice Shelf.

When glaciers rub across land, they produce what's known as glacier flour. It is a product of bedrock being ground clown by the moving mass. As glaciers move away, these remains are usually washed out into water. in particles sometimes too small to be noticeable to your eyes. But on land. soil and rocks contain iron oxides that often have rosy colors. like reds, yellows, and browns-and since the sea ice contained 500 times more iron than the glacier ice, Warren wondered whether the remains were responsible for icebergs taking on a green appearance.

He doesn't know for sure. He's hoping to secure money so that he can return to the area and study the icebergs themselves.