Here's an article everybody can relate to. After 42 hours of no sleep, 33 young adults under observation at Belgium's University of Liege were found to have significantly decreased problem solving and concentration. Other areas of the brain went relatively unaffected. All of the test subjects had their brain scanned and opened up even more questions about sleep, such as why some humans need more sleep than others.

Source: https://www.sciencenews.org/article/sleep-deprivation-hits-some-brain-areas-hard?tgt=nr