Why can't I remember where I left my car keys? Let's explore how our memory works and discuss some tips on how to improve memory.
Red, purple, green, blue. Red, purple, green, blue. Why is this important? Well, hold that thought.
Have you ever been about to leave your house in the morning rush and realized that you have no idea where you last left your car keys? Have you ever asked yourself, did I schedule that dentist appointment for today or tomorrow? What was it that I needed to get at the store, or what is my boss’s kid’s name again?
The way our memory works is a complicated process, the details of which neuroscientists are still trying to understand. Our brain’s efforts to store information can be broken down into three modes: working memory, short term memory, and long term memory, each controlled by different parts of the brain.
Short term memory works to store information for a brief amount of time, typically without any processing of that information. Much of this activity occurs in the prefrontal lobe, the section in the front of the brain that is found to be highly developed in humans compared to other intelligent species. (And, it’s the reason we have such prominent foreheads!) Research suggests that there is a capacity limit along with an expiration date for the memories held in the short term memory bank, but the details of those limits are still highly contested. The George Miller Theory from 1956 suggested that we could only remember seven units of information at a time in our short term memory (i.e. seven digits or seven names). However, it has since been shown that this number can vary a lot depending on the type of information, the person doing the memorizing, and the situation.
Working memory is also maintained only in the short term, but differs from short term memory in that it involves some kind of manipulation or organization of that information. For example, when you meet someone who tells you their name at a party, that name sits in your short term memory unless you manage to commit it to long term memory as well. If you decide to estimate how many people are at the party, those calculations will be run in your working memory.
The making of a long term memory is thought to require an anatomical change in the brain and to be inspired by a strengthening of a certain signal via repeated messages. Our neurons transfer information amongst themselves by sending signals across the gaps between themselves, gaps called synapses. When the same signal is repeated over and over, this sends the message that this information is particularly important. An apt analogy would be my response to getting a phone call from a number that I don’t recognize. If they call once, I will likely ignore it, but if they call back several times in a short span of time, I will start to place more importance on what this stranger might have to say.
The Man Who Couldn't Make Memories
Much of what we know about memory comes from Henry Gustave Molaison (otherwise known as H.M.). From the time he was a small child, H.M. had epilepsy so severe that doctors suggested removing a portion of his brain in an attempt to cure his seizures. So in 1953, when H.M. was 27, the neurosurgeon Dr. William Scoville removed two sections of H.M.’s brain, including both of his hippocampi.
The surgery was successful in that it reduced his epileptic seizures, but H.M. developed anterograde amnesia: he could no longer make memories.
Doctors quickly realized that H.M.’s lack of certain cognitive functions had nothing to do with dementia or intelligence. H.M. performed well on any I.Q. tests he was given. H.M. could also remember clearly anything that had happened before his operation. It thus became clear that, since the surgery had affected his ability to create memories beyond a few minutes, the hippocampus must be the area of the brain responsible for long term memory.