Learning and Memory

Many people would consider the ideas of learning and memory to be interchangeable terms. However, there is a subtle difference. Take learning to ride a bike. You might remember the moment you learned to ride a bike, but the memory of this moment is different to the knowledge you learned about how to ride a bike.

The way we know that this distinction is real is that there are lots of bits of knowledge that you learned at some point, but you can’t remember the specific moment you learned them.

According to the American Psychological Association, while learning is acquiring a skill, memory is being aware that you’ve acquired it. 

Learning is inseparable from memory as, without the ability to retain what we’ve learned, we cannot progress or apply what we’ve learned to our lived experience. So, understanding how memory itself works is pretty essential to understanding learning. 

Encoding in Memory

There are 3 main processes that characterize how memory works: encoding, storage and retrieval. 

Let’s imagine learning is like putting things inside of your backpack. Encoding is when you first put something into your backpack, storage is whether or not it stays in the backpack while you walk and retrieval is your ability to quickly find what you’re looking for. 

Unfortunately, unlike a backpack, our memory only holds onto about 5% of the things we put in it, that is – unless we routinely reach out to look for them. That’s why all 3 memory processes are so important.

In the first stage, the brain converts sensory perceptions into chemical and electrical charges. This process is called ‘encoding’ because it is putting what you see, smell and taste into code. The new encoded representations in the brain are called memory traces.

Imagine that you’ve got a beautiful photograph of a beach scene. When you encode it, you trace over the top of it to store the outline.

The second stage of memory is consolidation. After being placed in our short-term memory, the things we understand from the world around us are then grouped together and reorganized so we can remember them. For example, if you see a cute cat, the memory trace of it might be stored alongside other cute cats.

Storage in Memory

The final stage in the memory process is storage. This is when you take your sketched drawing and put it in your filing cabinet for later.

Currently, the scientific literature classifies memory into 4  main types: sensory, working, short-term, and long-term memory. The information we take in from our environment via our senses is stored by our sensory memory. Working memory then processes this information, moving it into our converting it into short or long-term memory. 

Short-term memory, as the name implies, is information quickly processed.  Short-term memories typically last for 15 to 30 seconds. Ever wondered why you lost your train of thought in the middle of a conversation while thinking about something else? Well, it’s because most adults have the capacity to store only 5 to 9 items in our short-term memory.

Once the memory traces, or rough notes, are encoded in our short-term memory, they are either discarded, or consolidated and moved into long-term memory. Long-term memory enables us to store information for longer periods – sometimes forever.

Memory Retrieval

The third stage in the memory process, retrieval, involves extracting information, skills and knowledge stored in our long-term memory. These are referred to as memory systems. 

Sometimes, words or facts may elude us because they were never stored in our long-term memory in the first place; other times, forgetting is due to an inability to retrieve the information from memory.

If we cast our minds back to the traced image analogy, if encoding is tracing the photograph, and storage is putting the trace into the filing cabinet, then retrieval would be like going and getting the trace out of the filing cabinet to look at. 

One example of retrieval in the real world would be recalling our revision notes when we are in an exam.

What is a Memory System?

Have you ever wondered why some knowledge seems impossible to forget, while other knowledge, once learned, seems to stick with us for life? Consider how easy it is to ride a bike even after decades of no practice. Then, consider how frequently you forget a word in the middle of a sentence or try to summon a name from memory and it eludes you. 

This phenomenon puzzled researchers, who eventually began to question the idea that there was one unified system to store long-term memories. The earliest, and probably most influential, distinction of long-term memory came from the Austrian psychologist Endel Tulving, who proposed that it can be broken down into conscious and unconscious memory.

Conscious, or Declarative, Memory

When something is remembered consciously, it resides in the declarative memory. This is conscious memory – stuff that you have deliberately and consciously memorized. For example, information you wrote on flash cards and deliberately committed to memory for an exam.

There are 2 kinds of declarative memory: semantic and episodic. 

Semantic memory refers to facts that we know and commit to memory, such as dates, names, and birthdays. Episodic memory is our personal recollection of events.

Semantic memory means knowing that the Earth is spherical; episodic memory means remembering the lesson where you were taught that the Earth is spherical.

Procedural Memory

In addition to conscious, declarative memory, there is also procedural memory – the things we remember unconsciously. 

Declarative memory includes facts and concepts, whereas procedural memory is made up of habits and skills. The knowledge we tap into when we ride a bike is stored in our procedural memory. 

Broadly, we can think of the difference between the 2 memory systems as remembering versus knowing. These are the channels we want to sharpen to enhance learning.

There are big debates about whether or not the same techniques should be used for different types of memory systems. This remains unresolved – a good bet for the time being is to try to incorporate multiple techniques for both kinds of memory systems.

The Man without a Memory

Different areas of the brain are involved in memory storage. The part of the brain that governs new declarative memory formation is the hippocampus.

In 1953, Henry Molaison unwittingly ‘invented neuroscience.’ Molaison had suffered debilitating epilepsy since childhood, and it was common medical practice at the time to remove parts of the brain to cure it. In a risky procedure known as a bilateral medial temporal lobectomy, his hippocampus was surgically removed. 

As a tragic, unexpected side effect of the surgery, Molaison developed a condition known as anterograde amnesia.

What is Anterograde Amnesia?

Anterograde amnesia meant that Molaison lost the ability to store or retrieve new experiences, meaning he lost the ability to form new memories. 

Through a decades-long collaboration with Molaison, Suzanne Corkin, a young postgraduate neurology researcher, discovered that Molaison had retained the memories that existed before the procedure but he had lost the ability to transfer the experiences he had post-surgery from short-term into long-term memory. In other words, throughout their 46-year relationship and the many tests Corkin conducted on him, it was always Molaison’s first time meeting the researcher. 

A series of experiments revealed that Molaison was able to acquire new motor skills, such as writing backwards while looking at his hand in a mirror. More significantly, despite not remembering having met Corkin before, he was still able to write backwards. 

This was a ground-breaking discovery as it proved that we use different parts of our brain for mental and motor skills, and for declarative and procedural memory. 

Confirming the Memory Pathway Distinction

Molaison’s ability to acquire new motor skills without a hippocampus showed that his procedural memory had remained intact. His tragic inability to recognize Corkin’s face or recall her name despite having met her hundreds, if not thousands, of times over the span of nearly 5  decades, proved that his declarative memory had been lost when his hippocampus was removed.

Subsequent studies of amnesic patients who acquired new motor skills by, for instance, learning to drive, confirmed Corkin’s findings about the distinction between procedural and declarative memory pathways, marking a breakthrough for the field of neuroscience. 

Corkin would eventually go on to become a professor of behavioral neuroscience and head of the Corkin Lab at the Massachusetts Institute of Technology. Henry Molaison lived in the perpetual present moment for the next 55 years of his life, until his death at age 83.

The Consolidating Role of Sleep

Have you ever wondered where the phrase ‘to sleep on it’ came from? The answer may lie in neuroscience. 

Research has shown that sleep aids learning and memory in 2 distinct ways. First, when we’re sleep-deprived we cannot focus our attention optimally and, as a result, we cannot learn efficiently.. Second, sleep itself plays a role in the consolidation of memory, which is critical for learning new information.

Rather than being a period of inactivity, our brain remains active while we sleep; running a “specific algorithm that replays the important events it recorded during the previous day,” and gradually transferring them into a more efficient compartment of our memory.

In other words, ‘sleeping on’ something is a powerful tool to boost learning and memory, and different sleep stages are beneficial for different tasks: REM sleep helps with procedural memory consolidation, and slow-wave, or ‘deep’ sleep, enhances declarative memory consolidation.

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