A new Northwestern University study reaffirms the importance of getting a good night’s sleep. By examining fruit flies’ brain activity and behavior, the researchers found that deep sleep has the power to clear waste from the brain. This waste potentially includes poisonous proteins that may lead to neurodegenerative (神经退化) diseases. “Waste clearance could be important, in general, for maintaining brain health or for preventing neurodegenerative diseases,” said Dr. Allada, senior author of the study. “Waste clearance may occur during wake and sleep but is greatly strengthened during deep sleep.”

Although fruit flies seem very different from humans, the neurons (神经元) that govern flies’ sleep-wake cycles are strikingly similar to our own. For this reason, fruit flies have become a well-studied model organism for sleep and neurodegenerative diseases.

In this current study, Allada and his team examined Proboscis (针状喙) Extension Sleep, a deep-sleep stage in fruit flies, which is similar to deep, slow-wave sleep in humans. The researchers discovered that, during this stage fruit flies repeatedly extend and move back their proboscises. “This kind of movement moves fluids possibly to the fly version of kidneys (肾),” Allada said. “Our study shows that this promotes waste clearance and aids in injury recovery.”

When Allada’s team disturbed flies’ deep sleep, the flies were less able to clear the waste from their systems and were more likely to be influenced by injuries.

Allada said this study brings us closer to understanding the mystery of why all organisms need sleep. All animals, especially those in the wild, are incredibly weak when they sleep, but research increasingly shows that the benefits of sleep, including crucial waste removal, are greater than this increased weakness.

About l.5 billion people speak English around the world.   But for more than l.1 billion of them, English is their second language-often with a noticeable accent.

“Someone's accent really reveals a lot about who they are and their identity. It will tell people what their native language is and probably where they come from,”says Marc Pell, a communications professor at McGill University in Montreal.   And according to Pell, one reaction to it can be a bias(偏见) against that person.

Previous research that has been done elsewhere showed that people who have an accent tend to be trusted less, simply because they have an accent. But accents aren't the only thing we listen for when we have to decide if we trust another person. Tone of voice also plays a role. Pell and his team wanted to know if people would trust a confident tone, even if it came from someone with an accent.

The researchers had Canadian English speakers listen to different versions of people saying neutral(无明显特性的) statements like “she has access to the building” while they were getting a brain scan in an MRI(磁共振成像) machine. Subjects heard someone say it with a confident tone with a Canadian English accent, an Australian accent or a French accent. Participants also heard the sentence with the three accents spoken in a doubtful or neutral tone.

The MRI scans showed that the participants had to use more brain power to decide if they could trust the statements said with the non-native accents. When the study participants heard the Australian or French accents, blood flow increased to the part of the brain that we use to process sound. They seemed to have to analyze that perhaps more carefully, or for a longer period of time to make this decision about whether they truly believed the speaker, especially when the speaker sounded doubtful. When asked, the participants reported not trusting either Australian or French accents-except when the statements were said confidently. It seems that confidence speaks for itself.

In the trailer (拖车式房屋)，Sischo was refreshing the snails ‘(蜗牛）accommodations--an ongoing routine that takes days of careful work. He had found a dozen of Achatinella bulimoides--a third of the world's population of the species. Once every individual was accounted for, he cleaned the cage and packed in new                    leaves. The work took much trouble, but the responsibility, he said, was like “a heavy weight sitting on you.”

The trailer is very vulnerable. It’s designed to keep away would-be thieved, and to resist hurricanes. But a fire could easily destroy it, or a disease could sweep through it. Last September , a mystery pathogon（病原体）appeared to have entered the trailer on leaves fed to the snails, killing almost an entire species. As sad as the event was, there’s no good way to insure against future catastrophe. The snails can’t simply be spread among zoos or other facilities: they need special equipment, experienced handlers, and a diet of native Hawaiian plants.

Consequently, it can be hard for the snails' minders to relax, even when they are outside the trailer. “How do you switch off when your decisions mean existence or extinction?" Sischo said. While action lightens the burden, yet with animals whose natural history is largely unknown, that action can be dangerous. "If you do it wrong, the snails die.”

Snails are neither intelligent nor beloved. Sischo's friends sometimes tease him about being "the strange snail guy' ; strangers ask why he cares. It's hard to convince people, but he insists that if he can just get them in the trailer, they will understand why the Achatinella bulimoides are worth saving. "People melt," he said“When you show them that the entire population is in this chamber, it hits them."