Memory is incredibly important, yet easily taken for granted. The movie Memento depicts this elegantly, showing a man who becomes completely transformed because he can’t remember anything that happened more than five minutes ago, despite knowing who he is. Poor sleep can fizzle memory in a similar way - you know where you grew up and who the president is, but people’s names evaporate and simple tasks have frequent hiccups. But there’s a much deeper and subtler way sleep deficiency affects memory.

When you learn something, your brain processes it and makes connections. You expect and anticipate what likely comes next. While listening to someone speak you can understand what they’re saying even if they mispronounce some words or mumble. You can follow the plot of a TV series while answering emails and browsing the web; the familiar story beats and character archetypes make this possible.

Sleep loss damages these memory connections. You might remember something but the meaning is lost. It is like being familiar with all of the words in a language but being unable to say a sentence. It can sometimes feel like having deja-vu. When it overcomes you, it’s hard not to be stopped in your tracks. The familiarity is there, but the understanding just refuses to show up.

What’s most frustrating about this failure of memory to coalesce into learning is the lack of empathy from others. People often take forgetfulness and missed recognition personally, especially when it happens over and over, as it is wont to do for the sleep deprived.