What happens to memory when people get older? We usually remember a lot of things from throughout our lives, but what would happen if one lived for an exceptionally long time? Would they forget more and more things from their past? Would they have difficulty remembering new things? Would their brain continue to grow to accommodate new memories? Would their head grow as well or would it explode?

Obviously there has to be a limit to how much can be remembered because there can be only a finite number of neurons. Does this limit memory or life expectancy?

The mechanisms through which our memories are encoded and decoded are still not thoroughly understood. We know a lot about it, but not specifically how it works at a low-level, anatomical level. It might turn out that memory is (essentially) limitless due to how it works (e.g., encoded in synaptic connections as opposed to individual neurons which could result in trillions upon trillions of combinations). However it seems more likely that there would be a limit in a way that is surprisingly similar to digital storage.

Speaking of digital storage, we now have storage devices that are incredibly small (~1.5cm³). Many gigabytes can be stored in a flash-drive that is about the size of a Tic Tac. If you filled the the brain’s memory center, the hippocampus (~3.0cm³), with tiny flash-cells, you could probably store about 64GB-128GB of data. That’s a lot, but not a huge amount. An android could certainly store much more, perhaps on the order of peta-bytes or even exa-bytes. The problem is in comparing to storage in the brain.

Johnny Mnemonic’s 80GB brain-capacity (even 160GB with compression) is surprisingly close to the aforementioned calculation which is impressively accurate considering that it came out in 1995 when a typical consumer hard-drive was the same size-as today but only about 512MB. Regardless, it isn’t quite analogous. The brain does not work like digital storage, so it’s not clear if or how/when a person could run out of room to store new memories.