1 . A workday filled with mentally challenging tasks can make people feel worn out and desire a relaxing evening of TV shows. A study led by Antonius Wiehler of Pitié-Salpêtrìère University Hospital provides an explanation for this familiar phenomenon.
Researchers arranged for two sets of subjects to work for over six hours. The first group was assigned a difficult version of tasks, while the second was given a simple version. They measured levels of glutamate (谷氨酸) that collected in the cognitive area of subjects’ brains, finding higher levels of the chemical appeared in the first group, although both groups reported feeling similar levels of tiredness after the daylong experiment. Glutamate helps learning and memory, but too much glutamate can give rise to brain cell damage.
Also, when researchers offered financial choices, as a measure of whether the difficulty of work affected subjects’ decision-making ability, those finishing harder tasks were more likely to choose to take home an immediate reward rather than wait for a larger cash-out at a later date. “Existing theories suggested fatigue (疲劳) is an unreal feeling cooked up by the brain to make us relax,” Wiehler says. “Yet our findings provide proof that cognitive work causes the collection of bad substances, so fatigue would be signal that makes us stop working but for a different purpose: to preserve normality of brain functioning.”
“Defining what fatigue is remains a challenge for the field, says neuroscientist Matthew Apps, “but it’s exciting that this experiment provides a reasonable alternative explanation that is of great help.” He notes some areas where these findings might come in. For people in jobs requiring intense focus, burnout can lead to damaging consequences. Preventing glutamate’ building may help maintain attention. Another area of interest would be researching clinical conditions related to fatigue. The presence of glutamate might reveal why patients struggle with fatigue.
For Wiehler, open questions remain. One limitation is their focus on the brain’s specific region, so what impact cognitively effortful work has on the rest parts remains to be seen. In addition, it’s not yet clear how the balance of glutamate is restored after rest. “Maybe it leaves the brain during sleep,” Wiehler says. “There’s tons of research to come.”
1. What was found in the experiment?| A．People who work longer expect higher rewards. |
| B．Tasks’ difficulty greatly affects levels of fatigue. |
| C．Tougher tasks cause more glutamate to build up. |
| D．Decision-making is linked with financial factors. |
| A．It bothers people in the workplace. | B．It mainly results from mental stress. |
| C．It signals the necessity of relaxation. | D．It serves as a protection for the brain. |
| A．Reliability of the finding. | B．The practical use of the study. |
| C．The challenge in the cognitive field. | D．Urgency to solve fatigue-related problems. |
| A．What limitations their experiment has. |
| B．Whether the balance of glutamate can recover. |
| C．Why rest is important for the brain to function well. |
| D．How demanding tasks affect other areas of the brain. |
