[music playing]

[music playing]

Eva, what's two opposite words, like two— like two words together that mean the opposite? What's that— what's that word?

Antonym?

No. No, no. Not like an antonym. They're grouped together like invisible ink— like invisible ink.

Contradictions?

No. Yes— no. No, not like a— not like a— it's a different— it's like—

What does it begin with?

I feel like it starts with an R. It's on the tip of my tongue.

Now, when you're in a tip of the tongue state, it's a very interesting question as to what can get you out of it.

As you may sense intuitively, one of the best ways to retrieve a memory stored inside your head is to come across something outside your head in the surrounding environment that is somehow related. We call this a retrieval cue.

If you just get the right kind of associative hint or cue, that can trigger the name. You may just be missing the right kind of retrieval cue to get you back to the name.

Sometimes all we need is a cue from something around us. And oftentimes, this can happen after the agonizing over remembering is long gone.

[music playing]

Eva, where does the word OxiClean come from?

I don't know. Why?

Oxymoron. That was the word. Oxymoron. Moron.

A retrieval cue is helpful, but there are other factors that aid in memory retrieval. Sometimes, returning to the environment we learned something in can be a powerful way to recall the thing we learned.

You might associate a particular historical fact with the professor who gave you a lecture on it in the course, the room that you sat in, or associating Adams with Jefferson. So we learn, in good part, by associations. And often, you remember somebody's name or a particular set of facts by relating it to something that you are already more familiar with and that easily comes to your mind. And that allows you to pull up the new bit of information.

By placing ourselves in the physical space where our originally learning process occurred, we prime ourselves to more readily retrieve memories that were encoded in that same space. This is called the encoding specificity principle, and it's the reason why it may be a good idea to stay seated at the same desk you usually sit in during class when it's test time.

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Your brain is more likely to recreate the pattern of activity that was there at the time you encoded it I everything else that's providing stimulation to your brain is the same as the time that you encoded it.

There are other cues that might prime us to recall certain memories more readily. If you're in a certain mood when you form a memory, it seems to be the case it's easier to recall that memory when you return to the same mood— the same state of mind— that you originally encoded it in. This is called state-dependent retrieval.

If the person's state in encoding matches his state in retrieval, the state itself— being happy, being melancholy— serves as the retrieval cue— a bridge connecting two moments in time. Here, a positive mood stirs the memory of another positive experience.

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So what is happening in our brains when we retrieve a memory?

What we remember really reflects what we encoded— what associations we activated at the time of encoding. And it's not just a literal recording of what happened.

The more we remember something, the more that something seems to keep its place at the table of memory. If we rarely or never call upon a memory, it's more likely that memory will be very difficult to retrieve, be it a word, a fact, a place we visited, a conversation we had, or a password we can't remember. In the brain, we see very distinct patterns of neural activity for someone who is trying to recall something unsuccessfully versus someone who is successfully retrieving a memory.

For the successful retriever, there is telltale activation of the hippocampus— the seat of memory formation in the brain— and a subsequent reactivation of many of the sensory areas in the brain that were originally responsible for encoding the memory. If it's an image, we'd expect to see activation in visual areas. If it's a song, we'd see it in auditory cortex.

This activity in the sensory regions when we recall a memory with specific sensory details may give us that feeling of seeing something right in front of our eyes— of having that song stuck in our head— but for the unfortunate retriever who is stuck in a retrieval tailspin, unable to get that word out, we see distinct activation centered in the left frontal lobe. And importantly, not the same kind of activity in sensory areas of hippocampus as we saw in the successful retriever.

[music playing]

Do you remember that?

What? What? The tree? [laughs]

No, not the tree. You don't remember?

Memory is this multi-stage process. You have information input that causes some change in the structure of the brain. In order to consciously retrieve that information, and actually use that information, you have to recreate this pattern of activity.

[MUSIC PLAYING

Oh. Oh, the picnic.

The picnic.

Yes.

Not the tree.

Yeah, this was one of the best days of my life.

Yeah? Cutie. That was a good day.

It was a good day. It was good times.

[laughter]