Learn How Predictive Timing Stems from Attention
Learn how predictive timing stems from attention and how that timing becomes out of synch and variable for people post-TBI.
See more of Dr. Ghajar's videos here.
If you look at the evidence in terms of cognitive deficits in patients with concussion, they're mainly attention. So it's attention, concentration, which is sort of sustained attention, working memory. Working memory is like I'm trying to remember some numbers and then recall them later on. It requires attention as well. Not to say that there are other cognitive deficits involved, but it really was central--and a lot of people have reported this-- that attention seems to be a central cognitive deficit in people with concussion. So you look at that and then the next question is, what is attention? And attention means a lot of different things to different people. Obviously arousal--you have to be awake to pay attention. You have to select something in the environment that you want to pay attention to. You have to process it, sustain your attention, not be distractible. All those things are sort of wrapped up into this definition called attention. But I was particularly interested in the patients that I saw. They seemed to be out of sync. What does that mean? You start looking at really why do you need a brain. You need a brain because you want to interact with the outside world. So if you want to interact with the outside world, there's a couple of things going on. One is the outside world is changing, it's dynamic. And the brain takes time to process information. You put those 2 together and you've got a brain that's out of sync because by the time--say you were playing tennis-- by the time you see where the ball is and you say, "Okay, I see it there "and I'm going to take a swing with my racket and hit it," the ball is gone. You have to start swinging your racket before the ball reaches there. It's the same thing with the brain. The brain has got to predict or time things before they actually occur. So when you're paying attention to something and you want to select something from the environment, you want to know what it is, where it's going to be, and when it's going to occur. That when part is very difficult. And we do it unconsciously. We learn, if somebody is speaking, the cadence of their voice, when the next word is going to come in, and we learn how to predict speech, and we can process it in synchronization. And so the hypothesis was that people with traumatic brain injury have a break in that circuit called the attention circuit, and they can't synchronize as well, so they're sort of out of time, out of step. This is sort of what I saw clinically. One way of looking at this is a helicopter flying across the sky. I've got to predict what the trajectory of that helicopter is and when it's going to be at a certain place, so my eyes track it, and it tracks in such a way that the helicopter remains stationary in my retina. And then I can process the information. I can see whether it's a helicopter or a bird. If I'm unable to predict the trajectory and the velocity of that helicopter, it becomes a blur. And what happens in terms of whether I know it's a helicopter or bird, sometimes I can see it, sometimes I can't. And what comes out of it is variability. If you look at people with concussion--and there's been a lot of research on this-- their reaction times are not just slow, they're actually variable. So there's this variability or this tremor in cognitive processes that's a result of predictive timing being off. Whereas people with traumatic brain injury seem to have a deficit that comes and goes, it seems to be variable. And so the hypothesis is that attention is a process to reduce performance variability. And it does that through predictive timing. When you're interacting with the outside world, you've got to predict things correctly. If you do that correctly, your performance then is spot on. If you don't, your performance is variable. And that's what we see in traumatic brain injury patients.
Posted on BrainLine February 9, 2012.
Jamshid Ghajar, MD, PhD is chief of Neurosurgery at Jamaica Hospital-Cornell Trauma Center, clinical professor of Neurosurgery at Weill Cornell Medical College and president of the Brain Trauma Foundation.
Produced by Noel Gunther and Justin Rhodes, BrainLine.