The most prevalent cause of memory loss

I have a hard time remembering things. It's not impossible — I have no issue recalling grocery lists and other banal stuff — but individuals will occasionally bring up conversations or events from years ago that I am completely unaware of. My mother, who is in her sixties and should, statistically, have a worse memory than I do, recently reminded me of my short-term memory loss when she remembered a previous Thanksgiving spent with my family by my college roommate. This is something I don't recall happening to me. I honestly thought my mother was lying until she showed me photos of the two of us baking pies together in my parents' kitchen.

What's going on? Why do some people's thoughts work like an iron trap, while others float around like goldfish?

When it comes to memory, there are three basic stages: encoding, consolidation, and retrieval, and issues can arise at any of these stages, causing you to forget things.

Poor memory is often a consequence of poor attention, which is directly tied to encoding. You forget the name of someone you've just met because, quite honestly, you weren't paying attention when they said it. You could be thinking about what you'll say next, who they remind you of, or what you'll eat for supper that night. Whatever the case may be, the upshot is that a critical piece of information – their name — did not make it into your memory. When you're not paying attention in class, during a discussion, or while reading a book, the same thing happens. You won't remember anything if you're not focused on what you're doing.

When a memory is processed in your short-term memory, which lasts about 30 seconds, it is moved to your long-term memory for consolidation. That can happen through repetition – you say a name enough times and it sticks in your mind. Other times, an experience is linked to an emotion, which helps you remember it. Because it was such a horrible day, most people recall exactly where they were when they discovered the Twin Towers had collapsed on 9/11. Fear and worry were running high. These emotions, as well as the stress chemicals that accompany them, cause you to pay greater attention.

Short-term memory is processed in the prefrontal cortex, whereas long-term memory consolidation takes place in the hippocampus, though other areas of the brain are also involved. Emotional memories, for example, trigger the amygdala, the brain's fear and arousal region, making them more deeply embedded and lingering. Long-term memories are moved from the hippocampus to the neocortex, the brain's top layer, which has more store capacity, in the last step.

The ultimate stage of memory is retrieval, which involves recalling information you've already memorized. A memory is reactivated in the hippocampus and neocortex during this process, causing the identical cells in the hippocampus and neocortex to fire again. Regularly recalled memories become stronger over time, which is another reason emotional memories are more memorable: you're more likely to revisit them.

Memory loss can be caused by cell death in the hippocampus, which is involved in both consolidation and retrieval. Dementia, severe depression, regular alcohol use, and even normal aging can all contribute to this. Scientists have revealed that new neurons can be produced in the hippocampus as well, most notably as a result of exercise, perhaps counteracting some of the region's cell and memory loss.

However, the most prevalent cause of memory loss is a storage problem. Your brain, like a computer, has a limited amount of storage and processing power. Old memories that aren't often recalled and so likely aren't too important (like apparently my Thanksgiving with my old roommate) start to decay in order to make place for new ones. This occurs as a result of the disintegration of synapses, or connections between brain cells, that form when you learn something or have a new experience. The stronger those synapses become and the easier it is to recall a memory, the more you reactivate it. Those connections will be cut out to create room for new ones if you neglect your memory.

Smartphones appear to be affecting our memories in an interesting way. Angela Lashbrook wrote an interesting essay for Elemental earlier this year about how photographing events can actually make them less memorable. The reason for this is that if you're too preoccupied with taking the picture or writing an Instagram caption, you won't notice what's going on around you. She suggests that you may be "subconsciously depend[ing] on the camera to'remember' it for [you]." The images, on the other hand, may jog your mind later on and assist you remember when you look at them. In essence, you've transferred your personal data to your phone's memory. Let's hope your iCloud account has more storage capacity than your head.