TedEd: The benefits of a good night's sleep

A TedEd by Shai Marcu

When you have a big test or performance coming up, and you've been working for weeks, but you're still a little bit unsure, do you sleep or do you pull an all-nighter? It turns out that sleep is much more important, especially for memory, than we often think. Sleep is actually a key part of your brain's functions, including memory. During sleep, our brain goes through a restructuring in which neurological pathways are strengthened and weakened to help us remember things. Herman Ebbinghaus found in the 19th century that we usually forget about 40% of the things we learn in the first 20 minutes. We can prevent this loss by transferring short-term memories to long-term memory. A structure called the hippocampus helps with this, and its function was determined in the 1950s by Brenda Milner with a patient known as H.M. The patient's hippocampus was removed, their ability to form both long and short-term memories was impaired. However, they were still able to learn physical tasks through repetition. The hippocampus takes short-term memories from neurons and strengthens and forms new synaptic pathways to preserve these memories. Memories made in times of strong emotion are usually easier to remember. Sleep is another important part of memory, especially the 2 deepest stages, known as slow-wave and REM sleep. EEG readings taken during these times show high activity between the brainstem, hippocampus, thalamus, and cortex. So the saying "sleep on it" might really be effective after all.

National Geographic: The Delta variant is serious. Here’s why it's on the rise.

By Sanjay Mishra

    As vaccination rates in the U.S. continue to fall, new concerns are rising about a more dangerous variant of COVID-19 that came out of India - the Delta variant. It already accounts for the majority of U.K. cases last week and 6% of the total cases worldwide, leading to the postponement of reopenings in that country. It is 60% more transmissible than the first Alpha variant, which was also 40% more transmissible compared to the original SARS-CoV-2 virus. It also seems to be more dangerous once a person is infected.

    The coronavirus mutates easily because its genetic information is in the form of RNA, which is prone to errors when copied. These random mutations can help a virus evade the immune system, make it weaker, or have no effect at all. In the case of the Delta variant, a series of genetic mistakes accumulated on the spike protein, which antibodies use to detect it. The mutations make it harder for antibodies to identify the virus and allow it to escape the immune system even after it is caught. Often, certain mutations that are beneficial to a virus evolve independently in many different areas around the globe and spread more quickly, with this mutation at location 681 quickly becoming more common.

    It also seems that this variant is also more resistant to vaccines. In the U.K., 31% of the patients with the Delta variant and needing critical care had at least one dose of a vaccine. With both doses, the Pfizer vaccine appeared to be around 88% effective, and AstraZeneca 60%. With one dose, they were just 51% and 33% effective. What has happened in the U.K. could happen in many other countries if people do not continue to be cautious. It is important that people not let down their guard.