Let's Explore our Memory: Wrapping Things Up

10 months ago

Okay family, it seems today is the last episode of our ongoing blog-isode themed:

Let's Explore our Memory

So let's wrap things up from where we ended in yesterday's blog-isode.

You see, for a while, it was thought that H.M. (Henry Gustav Molaison) and other patients with the amnesic syndrome could not acquire any long-term memories at all.

But further studies has shown that this isn't entirely so.

Yes

They can undergo classical conditioning, figure out the right path in a maze, and develop abilities such as tracing in a mirror and reading backward text.

With practice, their performance gets better and better.

But thing is, each time they are brought back into the experimental situation, they continue to insist that they have never seen the conditioning apparatus or the maze before, and that they don't remember anything at all.

The Question remains:

How can we make sense of these findings?

Anterograde amnesics, which we considered yesterday are evidently quite competent at retaining skills such as mirror-tracing (they do just about as well as normal people), despite their insistence that they don't remember anything about it.

On the other hand, they are utterly incompetent at many ordinary long-term memory tasks.

For example, they don't recognize an experimenter they have met on twenty different occasions. The one kind of memory is spared, the other is not.

What is the essential difference?

Some researchers believe that the essential distinction is between what computer scientists call procedural and declarative knowledge.

Procedural knowledge is "knowing how": how to ride a bicycle, or how to read mirror writing, basically areas in which the amnesic's memory is relatively unaffected.

According to this view, such skills are essentially programs (procedures) for executing certain motor or mental operations.

In contrast, declarative knowledge is "knowing that": that there are three outs in an inning, that raisins are made of grapes, that I had chicken for dinner last Thursday.

To know something procedurally does not guarantee that one also knows it declaratively.

For instance:

Professional baseball players "know" the procedures for swinging a bat, but not all of them can explain just what it is that they know.

Conversely, most physicists probably may be able to describe the underlying mechanics of a baseball swing, but few will be able to perform competently when given a bat and asked to hit a ball.

Neuroscientists who argue that this distinction explains what amnesics can remember and what they can't also believe that procedural and declarative memories depend on different neural systems.

A somewhat different explanation centers on the distinction between explicit and implicit memory. As we have discussed in previous blog-isodes.

The memories may be there, but they may be implicit, so that the patient doesn't know that he has them. As a result, he cannot answer questions like "Do you remember? or Do you recognize?" When they relate to events that happened after he got the brain injury.

Some evidence that the amnesics' deficit concerns explicit but not implicit memory comes from priming procedures.

When amnesic patients are shown a number of words and are later asked to recall or recognize them, they fail completely.

But the results are quite different when they are presented with fragments of the words and asked to complete them by forming the first words that come to mind.

Now there is evidence that something was remembered. The patient who was previously shown ELEPHANT and BOOKCASE will properly complete the fragments

L_P_A_T and B_O_C_S ,

even though he will not recognize either word if explicitly asked whether he'd just seen it before.

Interestingly enough,

this implicit memory effect will work only if the patient does not connect it with any intentional attempt to retrieve the word from memory.

If he is explicitly asked to recall the previously presented words by using the fragments as cues, he will fail again.

Now whether the explicit-implicit distinction is better or worse than the procedural-declarative at capturing the essence of what the amnesic can and cannot learn is still not clear.

It would seem that the two categories overlap, though they are probably not identical.

Perhaps there is no one distinction that does justice to the findings since amnesia is almost surely not a unitary disorder; not every impaired memory is necessarily impaired in the same way.

In any case, there are many further questions:

What is it about the development of declarative knowledge or of explicit, conscious access that makes them so vulnerable to brain damage?
Why is procedural knowledge spared? As we begin to find some answers, it is likely that they will shed light not only on the amnesic disorders but on memory functions in general.

Alright

So in looking back over this series (Let's Explore our Memory), we are again struck by the intimate relation between the fields of perception, memory, and thinking.

It is so often unclear where one topic ends and another begins.

To give just one example, consider memory search. As we saw in previous blog-isodes, trying to recall the names of one's high school classmates apparently involves many of the same thought processes that are called upon when we try to figure out how to solve a geometry problem.

To the extent that this is so, it is clear that much of memory involves thinking. The same is also true of perception.

For the perceiver becomes a thinker as he tries to solve perceptual problems and make sense out of ambiguous or impossible figures.

In the next blog-isode series, we will consider one super interesting topic:

Thinking

The Bus Stops Here for today:

Thank you, friends, for staying with me through these blogisodes. Your thoughts and opinions are always welcome and appreciated. I'd be happy to hear them. We will build on this in tomorrow's blogisode. Until then, stay safe, friends.