Our memory is by no means infallible. It is in fact extremely biased. You could even argue that nothing that has been stored in one’s memory is an actual description of events. It is reality as your brain with its unique networks has seen or experienced it.
The situation becomes even more difficult during recollection of a memory. Recall isn’t an exact copy of the information originally stored, as the brain reconstructs a past event. The result is a memory of an event that already has been interpreted twice.
Every time a memory is recalled and subsequently put back into storage a possibility of changes exists. The more time has gone by between the saving of the original memory and its recall, the greater the chance of modifications. Besides, the brain that is retrieving the memory from storage isn’t the same brain anymore that put it there. Networks come and go. Our brain is in constant movement because of everything we learn and experience.
Our memory is easily influenced as well. Research shows it isn’t hard to lead people to generate false memories. This isn’t only true for children, but also for adults. It took just a few hours to convince innocent adults that they had committed a serious crime in their teenage years, according to research of a British university. Over seventy percent of study participants internalised the stories they were told, full of rich and detailed descriptions of events that never took place. The false memories that were generated had the same kind of complex details as real memories.
Our memories are extremely valuable. They make us who we are. Memories are a prerequisite for feeling human. Severely impaired memory deprives people of a sense of personal continuity. It isolates them from emotionally or practically meaningful contact with the world around and renders them passive and dependent. Even mildly to moderately impaired memory has a disorienting effect. Someone who doesn’t have memories anymore has lost himself.
Notwithstanding their exceptional worth, even all those beautiful, sad, pleasant, and annoying memories can be reduced to electric currents in our brains. An efficient memory system requires intact functioning of many brain regions.
It is not known yet exactly how memories are stored in the brain, but bit by bit an interesting image has come up of how this process most likely is taking place. It is absolutely certain the brain does not record memories like some kind of photographs or videotapes and afterwards when the memories are being recalled, shows them on a type of screen in one’s head.
Widespread brain areas cooperate in learning and memory. Individual structures form systems for specific memory processes. Memories are stored in those parts of the brain that were involved when the information entered the brain in the first place. When you think of your grandmother you see her face, smell her perfume, feel her cheek that you used to kiss, and hear her voice.
All that information entered during encounters with your grandmother in different parts of your brain, dedicated to your eyes, your nose, your skin, and your ears. Many years later, when your grandmother has long passed away and you recall the cherished memory of her, the information from those different parts of your brain comes together in your working memory to make you see, smell, feel, and hear that familiar image of granny.
The hippocampus is a key player in memory. This tiny group of brain cells sits like a spider on the web of incoming and potentially preserved information. Many research projects have yielded proof that the hippocampus is critical to forming new long-term memories. It may be a temporary way station for information to enter long-term memory. As the parts of a memory are stored in the areas of the brain that initially processed the information, the hippocampus may serve to bind together the various components of a memory.
If desired, the amygdala adds an emotional touch to the memory, for instance the happy feeling you had when you were going to visit your grandmother.
For each task, another network of neurones is activated, but each neurone takes part in several networks and is thus involved in different tasks, be it with different partners. The more often a new task is being repeated, the smoother contacts between neurones involved will come about. This is due to the fact that a larger quantity of neurotransmitter, the chemical substance that transfers signals from one neurone to the next, becomes ready for use.
The other brain cells, the glial cells, play an important part in this process as well. Besides, the receiving neurone grows more receiving fingers, called dendrites, on which receptors are available for the extra neurotransmitter molecules. All this contributes to an even better information transfer.
As a result, connections between those neurones are less volatile. Information isn’t that easily forgotten anymore and passes from short-term memory to long-term memory. These names are made up by us humans. It doesn’t mean information actually goes to another place in the brain. The neurones involved have developed due to which they changed jobs and they are now working as part of long-term memory.
“Everything the brain produces, from the most private thoughts to the most public acts, should be understood as a biological process.”
Eric Kandel, Nobel Prize winner for memory research
A lot still has to be discovered about memory and how it is stored in the brain. Most interesting will be how memories are lost and what to do to keep the brain from losing important memories, especially in relation to dementia.
Although we normally use the word memory, it isn’t just one entity. It is an umbrella concept. In practice, several types of memory have been classified. Of course this is a classification we humans have made. Within the various schools of psychology, different classifications of memory are being used. Clearly, all this variability does not help comprehensibility of a topic of which we aren’t completely in the know anyway.
The scholars do agree on the fact that we have sensory memory. This is the recording of what we perceive with our senses. It is very short-lived and lasts from milliseconds to seconds. Sensory memory functions outside of our consciousness. We are not aware it exists and don’t have access to the information it contains. Needless to say, the brain does use this sensory information without us knowing it.
We use our short-term memory to keep some information for a short period, such as a telephone number. It has a lifetime of seconds to minutes and can only hold in general about seven plus or minus two items. We are consciously aware of the contents of short-term memory. Information automatically disappears from short-term memory, often because it has been replaced by something else we want to remember for a moment. If the information is important to us and we repeat it several times it may transfer to long-term memory.
Working memory is a broadening and deepening of the simple short-term memory. It is a limited-capacity store for maintenance and manipulation. It retains information over the short-term and it performs mental operations on its contents. This information comes from sensory memory and from long-term memory. An example: you walk in a street and from a window in one of the houses along the street a delicious smell of food enters your nostrils. You activate your working memory to think about which dish could belong to this delicious smell and to search in your long-term memory to find out when was the last time you ate this dish.
Information that has reached long-term memory will stay there for days, years or even a lifetime. Long-term memory contains two types of memory: non-declarative and declarative memory.
Non-declarative memory is about knowledge to which we have no conscious access. It contains among other things skills we have learned. When we learn to ride a bicycle for instance, at first it is very difficult and we have to put a lot of effort and all our attention into it. After a while, we cycle more or less automatically and don’t think about it anymore while we are doing it. Our cycling skill has been engraved in the unconscious part of long-term memory.
Declarative memory handles knowledge to which we have conscious access. It comprises information about our own lives and world knowledge we have learned. We can purposely recall these memories. Sometimes, you just can’t find what you are looking for, possibly because you are tired. In other circumstances, mainly because of neurodegenerative diseases like Alzheimer, someone won’t be able to retrieve memories at all anymore, because the brain has been damaged and the cellular network of a memory has fallen apart.
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