What happens in the brain when it becomes too hot?

"It was truly quite incredible. "The whole brain lit up," Anna Andreassen, a PhD student at the Norwegian University of Science and Technology, stated (NTNU). Living species, whether fish or humans, tend to perform worse as the temperature rises. This is something that many people have certainly experienced on a very hot summer day. But what occurs inside the body when the temperature rises too high? To find the solution, researchers at NTNU's Department of Biology used genetic technology with neurophysiological methodologies.

“我们对限制生物体耐热性的因素感兴趣。”当气候变化导致地球温度升高时，哪些生物会蓬勃发展，为什么？“我们决定看大脑，”安德烈森解释说。

Climate change causing heat waves

Heat waves that sweep across continents are becoming more common, and creatures that dwell in water are suffering dangerously high temperatures. Understanding what limits survival at extremely high temperatures is critical for forecasting how organisms will respond to climate change.

Andreabob体育打彩票ssen解释说：“几十年来，已经研究了热耐受性，并且温度影响大脑活动并不是什么新鲜。

Researchers at NTNU in Trondheim studied newly hatched zebrafish larvae's brain activity while progressively increasing the temperature around the larval fish.

"These fish have been genetically engineered such that when the neurons in the brain are active, they emit fluorescent light." While the larvae swim about, we can see this light through a microscope. These larval fish have the added benefit of being translucent. "We get to peer straight into the brains of living larvae," Andreassen explains.

Lose the ability to respond

然后，研究人员可以监测大脑活动，同时逐渐升高鱼游泳的水温度。bob体育打彩票在圈子里，肚子起来。”

The researchers prodded the fish larvae to see how they reacted. They poked the larvae's tails, which generally causes them to swim. But something strange happened when they increased the temperature.

"At a certain point, the fish ceased responding to the pokes." They were still living, but in an ecological sense, they were dead. "They wouldn't be able to swim away from predators or make their way to colder water in that condition in nature," Andreassen says, adding that this condition is only temporary in the small experimental fish.

安德烈斯（Andreassen）说：“一旦我们将它们放回较冷的水中，它们就会完全很好。”

热量关闭大脑

So far, the experiments have gone exactly as expected. They could also test whether the brain was perceiving visual stimuli by flashing light in front of the fish's eyes. As the temperature increased, the brain ceased responding to inputs and became fully dormant. But something strange happened when they increased the temperature.

"My entire head lit up. "The closest I can describe what we saw is a kind of seizure," Andreassen explains.

Normally, brain activity is only seen as little spots of light in certain areas of the brain. Under the microscope, the researchers could see how the fluorescent light spread out in a matter of seconds and covered the entire brain of the microscopic fish larva.

"We know that zebrafish brains have a lot in common with human brains - 70% of the genetic material is the same," Andreassen explains.

Following that, the researchers intend to examine glial cells, a type of brain cell.

“我们对加热过程中神经胶质细胞的活性特别感兴趣。”bob体育打彩票这些细胞对大脑的氧气递送至关重要，因为它们既bob体育打彩票评估氧气水平并调节血流和氧气供应。因为我们可以看到氧气水平会影响温度耐受性，所以一种理论是大脑关闭，因为神经胶质细胞不再具有调节氧气水平的能力。”bob体育打彩票

Differences advance evolution

To get a better understanding of what happened, Trondheim researchers began adjusting the amount of oxygen in the water the fish were swimming in while changing the temperature.

“我们很惊讶地看到氧气水平在调节耐热性方面发挥了作用。”当我们引入更多的氧气时，幼虫鱼在高温下的表现较高，大脑活动较高，并且比低氧气的鱼bob体育打彩票更快地暴露于上部热极限。

When evaluating the influence of oxygen content on temperature tolerance in various animals, researchers found contradictory results.

"Being "insensitive" to changes in oxygen levels may potentially provide an evolutionary advantage as the Earth's temperature rises."

"The data suggest that temperature tolerance differs between species." This could be a trait that determines whether a species can adapt to climate change or will perish as temperatures rise. Many species live in oxygen-depleted conditions where temperatures can quickly rise above ordinary. "They'll be extremely vulnerable," Andreassen predicts.

她以居住在浅水环境，河流或潮间带的物种为例。bob体育打彩票

"These are habitats where substantial changes in oxygen levels can occur, frequently concurrently with temperature fluctuations." In these settings, fish whose heat tolerance is limited by oxygen levels are more likely to struggle than fish that are not."

随着地球温度升高，对氧气水平的变化“不敏感”可能会提供进化优势。bob体育打彩票

"Animals that can retain nerve function under low oxygen levels may be the best at withstanding high temperatures," Andreassen says. (ANI)