Question: How does the brain record memories?
Antonio Damasio: In classical ideas about how the memory records memories of events, for example, there’s the idea that the brain processes a sequence of signals and the signals come from the perceptual regions of the brain and they sort of go in one direction to higher and higher order regions of the brain, like for example, the interior temporal lobe or the interior frontal lobe. And it is there at that point that the... both, the most complex perceptions of complex events as well as the most complex memories of complex events are formed.
So, the idea is that if you are listening to somebody singing or talking and at the same time seeing the person and sort of feeling yourself sitting in a chair because you are in a concert hall, that those separate impressions are only going to come together in very high order regions of the brain and that’s where they are going to be perceived, so that’s where you’ll have your sort of, film experience with soundtrack and whatnot. And that’s also where the recording is going to be made.
And there are a lot of reasons why this cannot work this way. About 20 years ago we were dealing with this problem in that we proposed the framework in which we said, "Well, first of all, we now are beginning to know that everything that moves forward in terms of signaling in the brain, does not move just in a forward direction, but as it moves forward, there’s also a feedback loop that comes to the origin of the feed forward." So, basically, we’re dealing with loops that advance, but also can come back on their tracks to the original point. That was something that was beginning to be known and that was very interesting because it opened up possibilities about the circuitry. So this is not just in one direction, but in multiple directions that included both the forward and the backward.
And the other thing is that there was clear evidence that when you lose, as a result of damage to the brain, when you lose regions of the brain that are very high up, like interior temporal lobe, or interior frontal lobe, lo and behold, you don’t lose the possibility of having a complex perception of the world. In other worlds, your filmic experience still remains. Nor do you lose the possibility of remembering the complex perception. In fact the only thing you lose is the possibility of dating and recognizing the uniqueness of the perception.
So, that discrepancy led us to propose this idea that there was a system of convergence that went over multiple hierarchies towards certain anchor points in the brain and that what the convergence was achieving was leading signals to a certain point, the convergence/divergence zone, and what was being recorded there was not all that was happening in your filmic experience, but rather the fact that something had happened back here that had happened simultaneously in this region, this region and this region. And then by dint of the feedback, the backward projection, we would have the possibility later on of the reactivating of the entire experience.
Now, what this achieved—that’s the notion of convergence/divergence zone. I actually only first called convergence, and I remember Francis Crick telling me, “Don’t call it just convergence, that’s what people are going to remember, they will never think about the divergence part.” And then I later corrected this because he was quite right. And so, the idea is that when you are asked to remember a certain experience that you had today in which you’re talking with person A, listening to the person’s voice, but you also are in a certain context, B, which is the context of a certain room in a certain building. You are going to have the separate recordings of the voice of the person, the sight of the person, the place—but those recordings are going to be reactivated only if another recording of the simultaneity of the event has been made in a convergence/divergence zone.
And so, you send signals forward through convergence and then divergence will allow for what I call, the process of retro-activation. And the retro-activation is going to take place in different sites at the same time, approximately, or in rapid sequence at those different places. Like for example, when we replay music in our minds.
And so what this does, just to finalize the story, is create a... solve a great problem of economy. In other words, instead of having to record every event that you are going through in your life every day with every kind of person, with the books you read, the things you see and hear and touch and smell, what you need to do is record conjunctions of the occurrence of certain events. And then out of the conjunction, you can replay, you can reconstruct. And so, memory in this perspective is always reconstructive. You’re always trying to get at some approximation of what went on rather than an exact recording of what went on. And that’s where the big difference between the recording in terms of a photograph or in terms of the celluloid picture comes. We are not like that. We don’t have these... all of this celluloid or polaroid pictures filed in some place and we don’t just replay them in a screening room. We have something that is at least both far more complex, but at the same time far more economic and also to a certain extent because of its fragmented nature, far more prone to error. All of these things come into the picture.
Recorded July 2, 2010
Interviewed by David Hirschman