Discussing “Functional Specialization in the Attention Network”

Why do we do what we do? This is a simple question, right? But it can have countless answers, of course.

You can think about the circumstances we're born into, the opportunities and threats we're presented with on a daily basis, all of that. But when it comes to the actions that we take, the most immediate influence on our behavior, in some sense, is our attention. What we pay attention to helps determine what we do.

So, among other things, attention is the brain's way of amplifying the important information for taking a given action while filtering out irrelevant information. This is what allows us to sift through the constant onslaught of light, sound, and other sensory information that is constantly entering our brains, and then pick out only what really matters for our goals, or to direct us toward the unexpected stuff that happens.

This kind of outlines two types of attention that I'll dive into later. But in a future video, I'm going to talk about how we can use the neuroscience of attention to focus more intensely and for longer periods.

In this video, I'll be discussing a paper that I found very useful throughout the process of learning about attention, and it's called "Functional Specialization in the Attention Network." That is by Ianc Feeble Corn—I apologize if I'm mispronouncing his last name—and Sabine Castner. It was published in the journal Annual Reviews of Psychology in 2020. That's a prominent journal.

This is a dense paper with tons of very useful technical information, so I won't be able to fully summarize the paper, but I'll be giving kind of a simplified overview of it.

So this paper, right, it's not about attention in general; it's about visual spatial attention. Actually, before I get into this, I just want to share this paper so you kind of know what I'm talking about here. Just to give the authors due credit, let me find it.

Alright, okay, so yeah, okay, so this is it: "Functional Specialization in the Attention Network" by Feeble Corn and Castner, 2020, from the Annual Review of Psychology. So anyway, just wanted to quickly show that.

Now, like I said, this is not generally about attention; there are many different forms of attention, but it's about visual spatial attention in particular. The authors define this, and I quote them here, as "the means through which a behaviorally relevant location receives preferential processing relative to other locations."

They give a really helpful example, which is of being on a busy street and then looking to a street corner where you're supposed to meet your friend. In that circumstance, you're kind of ignoring all the other information in that visual scene, right? All the passing cars and other distractions, and you're focusing in on that corner.

Now, I'll give an example from my own life that has to do with black widow spiders. In my backyard, there's a wall in the garden made of these wooden railroad ties—those big, like, I guess they're like 6x6 by 6, you know, wood things. Railroad ties, what they're called.

So I once found a black widow in a nest, like in the crack between two of those railroad ties, and it had hundreds—maybe not hundreds, but a lot—a ton of baby black widows crawling on the web. So, you know, I'm not afraid of spiders per se, but black widows and little tiny ones all over the place was not a fun sight to see in the backyard.

And my wife and my dog spend a lot of time in the garden, so unfortunately for this family of spiders, I sprayed the whole nest with insecticide.

Now, my point with all this is that every time I go in the garden, I look at that specific spot in that crack in the wall. It's just like my attention is drawn there to see if I can detect any movement that might indicate a new spider family, right? I haven't seen any yet, but if I do, I'm poised to go inside and get the insecticide.

So my attention network is preferentially processing that particular location while ignoring everything else in the garden. Now, when you use this kind of attention, you don't technically have to direct your eyes to the area of interest.

You can try this right now. You've got this scene in front of you, right? If you stare blankly at that scene in front of you—not at anything in particular, or maybe just fixate on one particular point—you can still attend to objects that you're not directly looking at.

So if you're looking at my face, you can shift your attention to, you know, the brain in the background over here without looking at it directly. But you're seeing it, and your brain is processing that location without engaging the motor system, without engaging your eyes, right?

So this is called covert spatial attention, and it's important because it shows that attention is separable from motor processes. Just keep that in mind; that's an important point here. It's not that your eyes have to be moving or looking directly at the thing that you're focusing on.

As you've probably noticed in your daily life, your attention can be captured by novel, unexpected features of the environment, or you can consciously direct it to certain locations, right?

For example, if a bright light suddenly flashes in your peripheral vision, you'll unconsciously, right, sort of effortlessly turn your head and direct your attention to that location. This is called stimulus-driven attention, sometimes also called exogenous attention.

On the other hand, as in the above example with the spider, you can consciously direct your attention toward, you know, that potentially spider-filled crack in the wall, and that's called goal-directed attention.

So the difference here is that stimulus-driven is sort of unconscious, and maybe involuntary is a good word, whereas goal-directed is more voluntary and endogenous, coming from within, and you're consciously pointing your attention at something.

Studies of attention have shown that whether it's stimulus-driven or goal-directed, spatial attention increases our brain's processing of that attended location. So if a task requires us to attend to a particular location, our performance on that task will be improved if we're cued to look at that location just prior to the execution of the task.

Going back to that spider example, if someone told you to look for spiders in my garden wall—if I told you, "Hey, look for spiders in the garden wall," like, "Okay, find the spiders," right?—you'd be more likely to see them, right? To find them if I told you to look specifically at the cracks where they tend to be.

That's kind of a simple example, but I just wanted to give that fact, right? That the cue matters; it helps us perform on these attention tasks.

So let's get into the neuroscience, right? I've talked about how the brain preferentially processes what's going on. How does this actually work in the brain?

As the authors of that study that we're talking about explain, it seems that there's a network of brain regions dedicated to visual spatial attention. So, as you might imagine, this includes the visual cortex, right? The areas at the back of the brain, mostly, that are responsible for your ability to see.

Excuse me. So that makes sense, right? But there are also these other two cortical areas that are very important: the frontal cortex and the parietal cortex.

While we're talking about spatial attention, a lot of this will translate to other forms of attention, as we'll kind of see, especially in that other video I talked about, that upcoming video. That'll be a little bit more clear, but especially this frontal cortex and parietal cortex.

So the frontal cortex is like what it sounds like; it's kind of this area at the front of the brain. I can show that really quick here.

So, as it sounds, the frontal cortex is part of the cortical part of this frontal lobe right here. So, you know, a pretty large chunk of the brain.

And then the parietal lobe is this sort of middle-ish part of the cortex here. So the occipital lobe is where a lot of this visual cortex is, and then the parietal lobe and the frontal lobe are also important for attention.

So I will close that out for now.

Okay, so in addition to these cortical areas, right, and I'll get a little bit more specific with which particular areas of those cortices I'm talking about, but there are also important subcortical areas as well.

So subcortical areas—subcortical areas that means below the cortex, right? Kind of deeper in the brain. This includes areas like the brainstem, especially the superior colliculus and the pulvinar nucleus of the thalamus.

So these are areas that are really close to kind of like the center of the brain. The brainstem is that thing that comes up and attaches the brain to the spinal cord, basically.

So these are evolutionarily older brain regions. We'll talk about what their particular functions are in the context of spatial attention as we go along.

So let's get back to the visual cortex, right? This area near the back of the brain that processes vision, processes visual information, allows us to see.

So this is really where the perceptual enhancement occurs. You can think of the visual cortex as a neuronal map of your visual field—a map made of neurons that is representing your visual field.

When you attend to a particular location, right, the neurons in that area of the map corresponding to that location show an increase in activity.

Okay, so that's what I mean by amplifying the processing of what you're attending to. So neurons outside that area aren't as active, right? That makes sense.

Okay, so this particular area shoots up in activity, so your brain is directing more resources to processing this location at the expense of all other locations in your visual field. So there's a trade-off there, right? You can't attend to everything all at once.

So how does the visual cortex know which areas to enhance its processing of? How does it know that?

Here, it seems that the frontal and parietal cortices—frontal and parietal cortices—this is where they're most important.

So again, the authors, Feeble Corn and Castner, suggest that the frontal and parietal cortices send signals to the visual cortex telling it which part of the visual field should receive enhanced processing.

In monkeys, researchers have shown that if you stimulate a particular area of the frontal cortex, which is called the frontal eye fields, the monkey's visual cortex shows changes in activity exactly as if the monkey was attending to a particular location.

This kind of shows this causal relationship between the frontal cortex, particularly this frontal eye field area, and the enhancement of processing, or sort of attention processes, in the relevant sensory cortex, which in this case is the visual cortex.

Now, this kind of stimulation can also improve the monkey's performance on tasks requiring spatial attention. So it's also doing kind of the same thing that attention does, right? Attention enhances. If you deploy attention on a spatial attention task, you're going to do better, right? Of course.

So similarly, in humans, people with damage to the dorsolateral prefrontal cortex have a harder time detecting visual targets.

So this suggests that this region of the frontal cortex, this dorsolateral prefrontal cortex—kind of the upper outer areas of the prefrontal cortex, like the most forward part of the frontal cortex—is similarly important for directing spatial attention.

Okay, so that's the frontal cortex, right? Now we'll mention the parietal cortex, but for now, just keep that in mind, right?

But it's not just the cortex. For a long time, there's been kind of this bias toward thinking just about the cortex when it comes to attention, but there are really these subcortical regions that play a very important role.

So we mentioned a couple of these, right? The brainstem, particularly the superior colliculus, right? This area is involved in shifting attention from one location to another.

So if I tell you to focus on this purple lamp behind me and then shift your attention to the brain on the other side, that shifting process depends on the superior colliculus.

This area of the brainstem, again, doesn't have to involve eye movement. I can just tell you, you know, "Look at this screen," shift your attention from one side to the other without moving your eyes.

Again, that shifting is dependent on the superior colliculus.

Now, a different area, like a little bit higher up in the brain, higher than the brainstem, pretty close by though, is the thalamus, particularly the pulvinar nucleus of the thalamus.

This one seems to be involved in re-engaging your attention at the new location. So again, you're looking at this purple lamp on this side of the screen, and then I tell you to shift your attention to the other side of the screen.

When you re-engage your attention at that new location, this involves the pulvinar nucleus of the thalamus.

Another thing about this region is that the authors note that it may play a particularly important role in coordinating attention across the cortex, across the cortical brain regions we just mentioned, like the frontal cortex, parietal cortex, even the visual cortex.

So they write that it may be something like, quote, "a cortical timekeeper." By that, they mean it adjusts the activity of various regions in order to optimize their communication during the deployment of spatial attention.

So it's kind of in that center of the brain, sort of like coordinating the activity of these regions.

Now, this makes a lot of sense given the pulvinar's anatomical connectivity. So it connects almost exclusively with cortical regions rather than subcortical regions.

So it's very interconnected with areas of the cortex rather than other subcortical regions, so it's in a perfect position to help coordinate that activity.

Now, as the authors explained, there are other areas of the thalamus that also play a role in spatial attention.

So they talk about the lateral geniculate nucleus of the thalamus. Now, this is important, especially for vision, because the lateral geniculate nucleus, or LGN, is essentially the relay station for visual information, meaning that it transmits visual information from the optic nerve to the visual cortex.

Okay, so basically coming from the eyes to the higher regions of the brain, this area is very important for that relaying of information.

Now, some studies have shown that this region activates more in response to the stimuli that a subject is attending to and less in response to stimuli that the subject is ignoring, showing it probably has this relationship with or this involvement in spatial attention.

So, okay, so sorry, this region also shows greater activity when subjects are anticipating the appearance of a target stimulus.

Okay, so it has this role in visual attention.

So those are some of the brain regions that are involved, but like everything in the brain, things work together, right? They work in networks.

It's never that one region has one function only and that it works alone. No brain region acts alone, as I like to say.

So let's talk about networks. Let's talk about top-down and bottom-up networks involved in attention.

So, explain what that means.

As I mentioned earlier, right, there are two basic types of visual spatial attention, and this is true for other types of attention as well.

So two types of attention: goal-directed, where we consciously direct our attention to specific locations or to specific things if it's not visual spatial, but goal-directed, right?

And stimulus-driven, so that's where our attention is captured by novel or unexpected features of the environment. Again, that flashing light just pulls your attention to it, right, without you really thinking about it.

So it seems that, as you might expect, these two types of attention recruit different networks of brain areas—overlapping but slightly different.

Okay, so goal-directed attention seems to be mediated by something called the dorsal attention network.

Okay, so let me show an image of this. But just before getting to that, dorsal is an anatomical term that refers to an animal's back.

So most animals, right, they crawl on all fours. Think of your dog or, you know, any most other animals, except like kangaroos and humans and, I guess, the great apes.

But most animals crawl on all fours, right? So their back is toward the sky and their belly is toward the ground.

For them, like think about a dog, the top of its brain is kind of toward the sky, so you'd say that's the dorsal part of the dog's brain, right?

But because humans, because we're bipedal, right? We walk on two legs, the term gets a little confusing when applied to the human brain.

But it's actually the same. So our dorsal, in the context of the brain, means the sort of upper part of the brain, high toward the top, really.

So let me just show what I'm talking about here; that'll be easier.

Okay, so this is a simplified graphic. It's helpful, you know, from Wikipedia.

So in blue, right, and these regions FF IPS—so that's frontal eye fields and the intraparietal sulcus—almost said circus.

These are kind of the main nodes of this dorsal attention network. And we'll talk about the ventral one down here too, but dorsal meaning kind of close to the top. You can see what I mean.

Alright, so let me turn that off for a second.

Okay, alright, so the dorsal attention network, right? Dorsal is an anatomical term, okay, that we just talked about.

So the dorsal attention network includes areas like we were just mentioning: the intraparietal sulcus, the superior parietal lobules, another area of the parietal cortex, and the dorsal frontal cortex.

So that outer area in that image shows the frontal eye fields, but in general, these areas are near the top of the brain.

Okay, that's goal-directed attention in a nutshell, right? That region or that network of regions is very important for goal-directed attention.

Now, returning to the other main type of attention, the stimulus-driven attention, this is mediated by the ventral attention network.

So let me pull that up.

Okay, so again, this is our ventral attention network. So in orange, this VFC stands for ventral frontal cortex, and TPJ stands for temporal parietal junction.

What you can see is, in this image, it's kind of a little bit hard to see, but on the right, they're showing the right hemisphere over here a little bit. The color for the TPJ and the VFC are a little bit more saturated, and that's showing that it seems like, especially with the ventral temporal parietal junction, that it seems to be right lateralized.

So the right temporal parietal junction is particularly important for this ventral attention network.

I don't want to get too caught up in the anatomy here, so let me just sort of explain this in words.

Okay, a lot of jargon, right? But one helpful way to remember these two networks, right? Helpful that the brain set it up this way, right, is that the dorsal attention network is top-down, okay?

Whereas the ventral attention network is bottom-up. And that's true both functionally and anatomically, okay?

So the dorsal attention network directs our attention in a top-down way that kind of forces the rest of the brain, including lower subcortical regions, to focus on a particular location.

It's like telling the whole brain, "Focus on those."

But in contrast, the ventral attention network works in a more bottom-up way, right? So it activates when something unexpected pops up in our environment and requires our attention.

So it kind of pulls our attention from that lower, you know, sensory level up to the higher cortical level.

So you can think of, you know, dorsal top-down, ventral bottom-up.

Okay, now the ventral pathway begins in, like I was saying, in the sensory processing areas and travels up to the higher cortical areas for processing.

And the opposite is true for the dorsal network. That's a simplification—probably oversimplified—but, you know, so for example, an important caveat that's offered by the authors is that the brain regions involved in both types of attention, top-down and bottom-up, goal-directed and stimulus-driven, are both involved in both kinds of attention.

They're all involved in both kinds of attention; it's just the degree to which they're involved, right?

So it's a relative activity difference rather than absolute.

Again, now I want to emphasize this paper. I'm skipping over a lot of important details, so the authors cover this much more comprehensively.

I'm not going to pretend that this video is a substitute for reading this paper if you want the full picture, the full detailed findings and everything that the co-authors are covering.

But I just want to mention that, right?

Okay, now something very interesting, like I had never heard about before reading this paper, that the authors talk about is something called the rhythmic theory of attention.

Now, this is actually their own theory—Feeble Corn and Castner came up with this theory—and they kind of contrast it to an earlier theory called the premotor theory of attention.

This section of the paper is fascinating, but it is quite technical, and I'm going to not get lost in the weeds here. I'm going to give a simplified, maybe oversimplified view of this theory. I hope not too bad.

But I'll just explain.

Okay, so the basic idea is that the attention network exhibits a rhythmic cycling between periods of enhanced and diminished perceptual sensitivity, and this cycle completes roughly every four to six times every second.

So that's once every roughly 250 milliseconds.

The authors proposed that during the first half, right, that enhanced phase, the brain is sampling a behaviorally relevant location, and so your perception is enhanced at that location.

Then during the second half, the diminished phase of the cycle, the brain is about to shift attention, or it's a window where it makes it easier to shift attention, and so perception is less sensitive.

So they offer evidence that during the enhanced phase, areas of the frontal cortex may be keeping attention locked onto one specific place while at the same time areas of the parietal cortex are enhancing sensory processing at that specific location.

So the frontal cortex is kind of holding that location as the object of attention, and then the parietal cortex is kind of, like, doing the—quote—doing the processing, enhancing the processing of that location.

Then during the diminished phase, when attention is about to be shifted to a new location, the sensory processing in the parietal cortex is suppressed, so that goes down, whereas the frontal cortex is allowed to shift attention.

Okay, so the authors argue that because the frontal and parietal regions represent this, like, a nexus, a kind of intersection of sensory and motor functions during the enhanced attentional state, the frontal and parietal cortices may exhibit stronger functional connectivity with perceptual nodes of the attention network, like the visual cortex.

Okay, so during that enhanced phase, holding attention on a specific object, processing it more intensely, and those frontal and parietal regions are more tightly coupled with the visual cortex.

Then during the diminished attentional state phase, right, the frontal and parietal cortex might exhibit greater functional connectivity with motor-related nodes of the attention network, like the superior colliculus, that region that's important for orienting and shifting our attention.

Okay, alright, so I know that's a lot. Even so, it is simplified—again, probably oversimplified—as an explanation of this rhythmic theory of attention.

So any errors, right? Any factual errors are mine and not the authors. Blame me, right? As I like to say.

So I urge you to read this paper if you want to get much deeper into the subject. It is quite technical but extremely interesting, in my opinion.

Okay, so the one thing I really like about this paper is that in the beginning, they give that great vivid example of being on the street corner, and at the end of the paper, they kind of pull everything together back into that example.

So I just want to summarize this example, this vivid sort of real-world example of how their theory works.

Okay, so they bring us back to that street corner, right? You're looking for your friend at a particular street corner. You're standing on the street looking for your friend at a street corner you agreed to meet there, right? You're like, "Where is he?" You know, kind of looking around, trying to filter out all the irrelevant information.

So you're enhancing sensory processing in that region of your visual field using that goal-directed attention process.

They explain that visual processing at this spot briefly diminishes roughly every 250 milliseconds due to that rhythmic attention pattern.

Now, this temporary dip in your focus increases the chances of you noticing something unexpected, like a person, maybe your friend, waving in your peripheral vision or slightly, you know, to the right or left of where you're actually looking on that street corner, right?

So it's important for attention. It's not just that it's diminished; it's not bad. It's like if you were hyper-fixated on one spot for too long, you might miss actually important information for your behavioral goal.

So shifting your attention to that spot requires mentally, like neurologically, letting go of the original location and focusing on that new location.

These shifts are supported by different neural networks and mechanisms that manage each stage of attention.

Okay, so that is the paper in a nutshell—oversimplified to be sure, but I mean, maybe not, you know, oversimplified. I think we captured most of the important details of how visual spatial attention works.

But I want to return to this question that I posed at the outset of this video. So how—why do we do what we do, right?

We can now see that visual spatial attention, how it works, and so we've gained some insight into how it influences the actions we actually take.

So, for example, we've seen that there's two basic forms of attention, right? Goal-directed and stimulus-driven attention, and these are mediated by partially different, partially separable brain networks.

But we've also seen that our brain rapidly cycles between enhanced and diminished phases of sensory processing.

So during the diminished phase, we're particularly vulnerable to distraction because, by definition, we aren't focusing as intensely during this phase.

So that might start posing some questions in your mind, like how do I focus better? How do I kind of take advantage of these two different forms of attention and this rhythmic cycling process?

Now, that's exactly the question that I will be talking about in an upcoming explainer video.

So if you're watching this current video after that one, that new one has been published, which it hasn't yet, it should appear somewhere around here, and there should be a link to it in the description of this video.

But anyway, thank you so much for watching. I hope you gained some insight into your own attentional processes, know a little bit more about how your brain works, and, as always, I appreciate your time and your viewing of this video.

I'll catch you next time.