Did you you forget how your memory works? (pun intended).
(No Dad, I won't be discussing gigabytes or megabytes here)!
When we say memory what we are really talking about is our ability to 'consolidate' our short-term thoughts into long-term thoughts. This consolidation is done by strengthening the nerves in various parts of your brain (mainly, the hippocampus) to ensure that they will fire more readily and consisently next time. But how do nerves get stronger, exactly?
When neurons (nerves) in the brain are stimulated, they mainly use the excitatory neurotransmitter called glutamate (an amino acid-part of many protiens). When some glutamate receptors receive the neurotransmitter they simply 'fire'- just like a copper wire from a cord being plugged into the wall. But sometimes, the impluse reaches a specific type of glutamate receptor that changes the neuron. It makes it more excitable by increasing the efficacy and number of glutamate receptors. In short, it's glutamate that can make these neurons 'stronger'. (Anyone who is interested in the cell signaling/genetic explanation, grab a copy of Neuroscience by Bear, Connors, and Paradiso...it's just too much to type out)
I know what you're thinking. What the heck is glutamate, right? Well it's the main part of the food additive MSG (monosodium glutamate) commonly found in western-chinese foods. It's health effects are currently being investigated, and it may play a role in the development of some diseases such as asthma and obesity- nothing conclusive though.
It is also the major part of the 5th taste called umami. We're all familiar with the other 4- sweetness, sourness, bitterness and saltiness. Ever wonder why chinese food tastes just a little different? Some scientists would say that you're tasting umami. Others would say it's all in your head :) Which side are you on?