Similar to our language abilities, I think we often take the importance of our memory for granted. We may even complain, “Oh, I have a memory like a sieve!”. But if you read about amnesiacs, people who lost their memory due to brain damage or infection, you’ll be surprised (or shocked) how much of our life and normal functioning actually depends on memory. Anyway, I was when I was reading a book called Musicophilia by a famous neurologist Oliver Sacks.
In Chapter 15, In the Moment: Music and Amnesia, he describes a patient who, being in his mid-forties (!), got a bad brain infection, herpes encephalitis, and afterwards was left with a memory span of just a few seconds. In addition to not being able to form new memories, he had a retrograde amnesia, “a deletion of virtually his entire past”.
Can you imagine how he felt? He was in a terrible state:
‘When he was filmed in 1986 for Jonathan Miller’s extraordinary BBC documentary, Prisoner of Consciousness, Clive showed a desperate aloneness, fear, and bewilderment. He was acutely, continually, agonizingly conscious that something bizarre, something terrible, was the matter. His constantly repeated complaint, however, was not of a faulty memory, but of being deprived, in some uncanny and terrible way, of all experience, deprived of consciousness and life itself. As Deborah [his wife] wrote,
It was as if every waking moment was the first waking moment. Clive was under the constant impression that he had just emerged from unconsciousness because he had no evidence in his own mind of ever being awake before…. “I haven’t heard anything, seen anything, touched anything, smelled anything,” he would say. “It’s like being dead.”’
I guess after this story I really don’t feel like joking or complaining about one’s poor memory. And I’d like to share an interesting video with you where a neuroscientist, Daphna Shohamy, PhD, explains ‘memory’ to 5 different people: a child, teen, a college student, a grad student and an expert. Probably, ‘explains’ is not the best word because with the last three people it mostly resembles a talk, but still.
Where is memory in the brain?
In the video you’ll hear references to different parts of the brain, so I think this will be useful: in the brain memory supposedly resides in
- the cerebellum (procedural m.),
- the hippocampus (declarative m.),
- the amygdala (emotional learning),
- the basal ganglia and the striatum (motor skills and implicit m.),
- the frontal lobes (important in working m. and making decisions based on our memories),
- the temporal lobes (autobiographical m. and recognition m.).
What types of memory are there?
I also thought that a reminder of the types of memory will help you take away more from this video, so I looked them up:
1) Sensory memory holds the information received from senses, for less than a second. It’s automatic and out of our cognitive control. Its types are
— iconic, which is obtained through sight;
— echoic, which is auditory;
— haptic, which is through touch.
If a sensory experience keeps coming back, we attach other memories to it and it moves on to our short- or even long-term memory,
2) Short-term (or working) memory encodes information acoustically and holds it for a minute maximum. Its capacity is usually believed to be 4-5 items but can be increased with practice.
3) Long-term memory is divided into
— Explicit memory, or declarative. This type requires our conscious storage and recollection of information, experiences and concepts. It requires gradual learning and can be
- Episodic memory, which stores specific personal experiences;
- Semantic memory, which stores factual information.
— Implicit memory, or procedural. This one refers to memories acquired (usually quite rapidly) and used unconsciously such as
- skills (e.g. knowing how to get dressed),
- perception (e.g. telling apart different smells),
- emotional learning (e.g. being afraid of dogs)
- category learning (e.g. breeds of dogs, movie genres)
- priming, or pattern completion (e.g. you are presented with half a letter of the alphabet and you can complete the other half).
But in the video Daphna Shohamy says that her research “pushed against that distinction between memories” and “allowed us to … think of them less as multiple completely separate independent systems and instead to try to understand how they really work in concert with each other”.
So it’s more about how different parts of the brain are connected (as in a network) and work together when we use our memory to make decisions and predictions about the future (yes, memory is not only about the past, it’s crucial for our future).
Enjoy the video! 😊