Our memories are our best friends and our worst enemy. This paradox doesn't even tell us which level of functionality our memory is operating at when when we experience these personifications. It can be absent when we want to get our closest friend's attention or it can show up when we think back to an embarrassing moment we with we could forget.
Even though our brains seem almost laissez-faire about how it records and regurgitates information there is a system. It reduces most things into 3 categories; sensory, sort term and long term memory. With these three memory types we catalog our sensory stimulus into discernible thoughts that we can use later to our wants. Then, as the situation demands, it calls upon those sensations to solve whatever problem you have presented it. We do this by reconstructing things based upon what can be recalled. In this way it depends on the "power" of the memory. Say you really want to remember a fact, for a test as an example, you will go over the information several times to make it "stick". The memory also might be powerful enough to stick on its own. say for example your favorite birthday party. You didn't have to have the birthday more than once, but the experience was so strong that it sticks with you so you can enjoy it later. These two examples are taking stimulus, sensory input of your eyes and ears, putting it into short term memory so you can react to it in the moment then transferring it to your long term memory so it can be accessed should the need arise.
So where does all this take place in the brain. Well that isn't easy to say. There is evidence that our hippo-campus is the action center where memory takes place, but the truth lies more in the way a smell permeates a room, to take an example straight from
Lilienfield, it is a little everywhere. The true mechanism however is Long Term Potentiation (LTP) or the increasing strength of connections between neurons of the brain.
Memory is a complicated thing that we have to work at, it doesn't happen all by itself and will therefore always have a variable amount of reliability. The take home is that it is as perfect as we are and that is good enough for me
