What is Memory Consolidation?
Memory consolidation is the process of stabilising a memory after the initial acquisition process mentioned in Making Memories Part One. It is usually considered to consist of two specific processes, synaptic consolidation (which occurs within the first few hours after learning or encoding) and system consolidation (where hippocampus-dependent memories become independent of the hippocampus over a period of weeks to years).
Repetition is a significant part of consolidation, especially with regard to procedural (things we learn how to do) and semantic (factual) memories, which is why things that we have learned ‘by heart’ as a child tend to stick with us. It is important, however, that what we learn is also meaningful to us as that way we can build upon what we have memorised and use it in different ways. That is the point at which school or book learning becomes knowledge.
Memories can Change
Even the most consolidated memories can remain plastic, in other words, they can be changed in small ways over time. This is particularly so of episodic or autobiographical memories, our memories of the things that have happened to us in our lives, so when we talk to friends and family about events in the past their memories, which will be different to ours as they have their own perspective, may influence ours and we may build up a bigger picture of an event or give it a particular bias.
We can also remember an event from the past and give it negative or positive embellishments which through repetition then come to be remembered as the truth or fact, even if that was not actually the case. This is sometimes referred to as the malleability of memory. We may ‘remember’ something after an event and embellish it, particularly with the benefit of hindsight. Therapists and courtroom lawyers have much to say on the unreliability of the human memory over time for this reason.
Our memories are not stored in any one specific part of the brain but are stored like pieces of a jigsaw in the different parts of the brain that handle the components of the whole. For instance, think back to a childhood memory of a picnic or outing in the country. That memory will include visual, olfactory and auditory segments and these will be handled by the different parts of the brain that process that particular sensory input. When you remember that event you will remember not just who you played with but also the smells, sounds and colours associated with that event. This is why sometimes a particular smell, sound or sight can take us right back to a particular situation or event in our lives.
Some things you will remember in greater detail than others, depending on the emotional stimuli of the situation as well as whether the location is somewhere that you went to frequently, so the memory is reinforced, or if this was a one-off. If it was an annual event then in retrospect it can be difficult to separate out the individual memories of any one specific event unless something exceptional happened. Do you remember all the Christmases of your childhood as separate events or does the one where you received the bicycle you especially wanted stand out?
The Importance of Sleep
Sleep is essential to the consolidation of memories and if you are studying it is really important to make sure that you get enough good quality sleep. This gives your brain time to do essential housekeeping and consolidate memories from short term to long term. It is also important to break up your study periods over time with proper rest and meals in between rather than cramming at the last minute.
Research has proven that we will remember more if we study for an hour a day for 7 days than if we try to learn the same amount of information in an intense cramming session of 7 hours. Reading aloud can also help us to remember difficult material as this creates an auditory memory of the information as well as a visual one. If you are reading aloud you also have to pay more attention to what you are reading and can’t skim or skip over bits of text that you don’t understand or that don’t interest you.
It is believed that in principle the undamaged human brain has an infinite capacity for storing memories and most memory problems are believed to lie with encoding or recall/retrieval issues rather than with the memories themselves. Other theorists believe that existing memories may be overwritten somehow by newer ones and eventually decay if they are not retrieved.
There is still so much to be learned about this fascinating aspect of ourselves, who knows when we will have all the answers?