Did You Read This Already?

“Without the hippocampus, it’s unlikely you would be able to remember reading this article.”

Photo credit: Laura Dahl.As a new academic year kicks off, Aoife Hardesty delves into the science of memory.Memory is defined as the mind storing and remembering information, and we define ourselves largely by our memories. Memories shape who we are and what we know. Everything we learn in life depends on memory forming in our brain and being processed. As a result, dementia patients or people with severe memory loss change into very different people.We depend on memory for all learning events and different memory techniques can be employed to use our memory system more effectively.  The method of loci involves visualising mental places to store memories and is sometimes called a “memory palace”.This technique of memory storage involves a space -- real or imaginary, outdoors or a building -- not necessarily a grand palace. Whatever it is you are trying to remember, you create mental associations between it and locations within your “palace”. This then enables you to walk around this space within your own mind and “see” the memory associations, which trigger the memory.Another way of approaching this form of memory storage is to journey through the place, and have information deposited at different stages of that journey.A mnemonic is a memory aid, which helps with the storage of information. Common mnemonics include rhymes to help remember the number of days in each month, songs to remember the letters of the alphabet, acronyms where each letter in a word stands for another word.Mnemonics work by association, the information you’re trying to remember is associated with another piece of easier to remember information, or a place in your “mind palace”. The harder info is linked to the easy info and so remembering one triggers the other.Our brain cells are dynamic things. They change their shapes and connections regularly throughout our lifetimes. When objects become associated with each other, the brain cells responsible for the two separate objects or info are connected, and if this association is repeated, the connection becomes stronger until it is very hard to get rid of the association.A familiar everyday scenario in which this happens is how a certain song can remind you of an exact moment in time – whether it be a flashback to the beach in Majorca, your first kiss, or walking home in the pouring rain after a miserable day in school.In order for the brain to hold onto memories, memories generally have to be retrieved and processed so that they can eventually enter long term storage; this processing involves the hippocampus, and is the reason why you may have to study the same thing several times before you feel that is solidly implanted in your brain.The hippocampus, named due to its semblance to a seahorse when isolated from the rest of the brain (hippo is horse in Latin, and kampus is sea monster), is a brain structure located in behind your ears. The importance of the hippocampus in memory formation was seen very obviously in the case study of HM, Henry Molaison, a patient who was studied from 1957 until he died in 2008, aged 82 years old.Molaison suffered from severe epilepsy and to alleviate his condition underwent brain surgery. During the surgery, sections from his brain were removed, including the hippocampus. Following the surgery, Molaison could remember events prior to the operation and had short term memory, but was unable to form long term memories.The hippocampus is required for the processing needed to turn short term memories into those stored for the long term, and is the structure relevant for those mnemonics discussed above. Without the hippocampus, it’s unlikely you would be able to remember reading this article, the information within it, or even the rest of this newspaper.