Dr. Jeremy Sharp (00:01)
Hey everyone. Here we are. We’re back. We’re getting into it. All right. So I’m going to start this episode with a brief discussion of the neurobiology of checking out or testing fatigue. So I think to understand testing fatigue, we do have to move beyond just being tired. It is more than that. We’re talking about actual cognitive fatigue, which is a measurable decline, essentially in executive control.
All of us have experienced this. We really wrestle with this, you know, as a practice that tends to do testing all in one day rather than breaking it up over multiple days. We do wrestle with cognitive fatigue. Now, some of that is by design to make sure and catch our clients at times when they are both fresh and not so fresh. But there are different perspectives on this, of course, and that’s why some of you break up your testing days in multiple sessions, among other reasons. So we’re going to get into this.
Dr. Jeremy Sharp (00:54)
research in cognitive neuroscience, specifically around this concept called expected value of control theory or EVC theory, gives us a clearer picture of what is happening under the hood when you’re experiencing some fatigue or checking out with your client. So the brain is kind of continuously performing a little bit of a cost benefit analysis for every task that it undertakes. right. This process is
primarily mediated by the dorsolateral prefrontal cortex, which is kind of like the CEO brain, and the anterior cingulate cortex. Some of you are like, yeah, absolutely. Some of you are like, I don’t know about that. And some of you are like, I don’t even know what you’re talking about. That’s OK. That’s the most I’m going to say about the anatomy and neuroanatomy of this process. But essentially, when a patient is fresh, the
Dr. Jeremy Sharp (01:46)
ACC, interior cingulate cortex, signals that the reward of completing the task outweighs the, quote unquote, metabolic cost of the effort. But as fatigue sets in, the brain experiences a buildup of glutamate in the lateral prefrontal cortex. And that is troublesome. So a study published in 2022 found that high demand cognitive work causes glutamate to accumulate in the
extracellular space of the prefrontal cortex, which physically makes further exertion taxing on the brain and can even be somewhat toxic. That seems like a strong word, but that’s what the researchers say. essentially, the brain’s biological accounting system goes into like a self-preservation mode. It stops spending energy on high-level cognitive tasks to prevent further metabolic debris.
Dr. Jeremy Sharp (02:42)
from building up. OK. So if you want a very simple metaphor, it’s like the more you ask the brain to work hard, it is sort of building up this trash or debris, so to speak. And if it gets to be too much, then it sort of poisons the system and leads to a little bit of a shutdown. So this ties directly into something we’ve discussed on the podcast before, mainly in the context of AI and
writing and that is cognitive load theory. So you can think of working memory as any number of things but you know the metaphor I’m picking here today is a glass of water. So intrinsic load is the water itself. It’s kind of like the difficulty of the task and then you have extraneous load which is you know the ice cubes. Other things that have to go on the glass. So these are like distractions and bad lighting or you know the clients
Dr. Jeremy Sharp (03:36)
you know, physical sensations or discomfort. And when you put too much in the glass and it overflows, the client can no longer process information effectively. And, know, during a six hour assessment session, that glass is almost always overflowing by the afternoon session. So there’s a little more nuance to it though. So we’re going to talk about the process of failing, what fails first and
which cognitive functions are most sensitive. You can probably guess, but I’m going to talk about it. not all cognitive functions are created equal when it comes to fatigue, right? Research in our field, of course, suggests a clear hierarchy of vulnerability. Executive functioning and fluid reasoning tend to be the first to go. This is probably not a surprise to anyone. I feel like poor executive functioning, just…
Dr. Jeremy Sharp (04:29)
it’s the first thing to take a hit in pretty much any scenario that’s non-optimal. also the case here, so for example, a task like the Wisconsin card sort or some kind of like matrix reasoning, something like that, they require pretty heavy lifting. Once that effort versus value calculation shifts toward energy conservation, these scores or effort
on these tasks will likely go down pretty sharply. And as clinicians, we might see this and say, oh, this could be a sign of executive dysfunction or poor reasoning or whatever interpretation we want to assign to that task. So executive functioning and fluid reasoning are the first to go. On the other side, though, crystallized intelligence, like vocabulary or just general fund of knowledge,
is remarkably fatigue resistant for the most part. for us, I think this creates a little bit of a dangerous diagnostic trap where your patient might still sound articulate and kind of with it during verbal tasks, which is masking the fact that their fluid reasoning and attention networks have largely gone offline. So they might appear to have it together, but in fact under the hood that
trash or debris is building up that glutamate is building up. So many clinicians, you know, report that processing speed tasks like coding, for example, show a little bit of a U-shaped curve. Now, this is not like totally validated in the research, but, you know, a lot of people report this U-shaped curve where performance dips in the middle of the day and then sometimes like rallies at the end when the patient sees the finish line. But
Dr. Jeremy Sharp (06:11)
Again, don’t know statistically if that is actually reliable or not. It seems to differ across different populations. And we just need more data on that. again, just to recap, executive functioning and fluid reasoning are going to be the first to go. But crystallized intelligence, vocabulary, fund of knowledge, et cetera, is generally going to remain intact. So you end up with a wicked combination that you need to be aware of there. All right.
So what can we do to actually change things up or adapt to combat this fatigue during our testing days? We can’t change the biological limits of the human brain, of course. But we can change, I think, how we interface with it. So these are, I’m going to give you like three concrete practices that you can implement to try to combat this phenomenon. So the first one.
I guess I will call it like the heavy to light rotation. And some of you are probably already doing these things either deliberately or intuitively. But I’m just going to kind of put a name and a little bit of a structure to it. And some of you, this might be new. And that’s totally OK, too. So like I said, the first thing is what I’m calling the heavy to light rotation. So this is just your permission to stop following the administration manual standard order if it places your most difficult executive functioning tasks at the end.
You want to front load things that require memory and coding, fluid reasoning, et cetera. Put those in the first 90 minutes, if at all possible. And then put your more low effort tasks like motor speed or cancellation or personality inventories and things like that for the last hour of the day, if at all possible. Second strategy is something called like
a 90 minute pivot and a little bit of a movement reset. So pivot and reset. Research on just like circadian rhythms tend to show that, you know, our cognitive performance generally cycles every like 90 to 120 minutes. So don’t wait for the patient to look tired, right? You can schedule a mandatory quote unquote movement break at the 90 minute mark. That’s always safe. You know, err on the side of
shorter versus longer. Now, there’s a lot of variability here. So, you know, for kids, it could be shorter. Sometimes you’ll get super focused adults who can maybe push to 120 minutes. the idea is to, again, plan, you know, movement break at a specific time where you get them out of the chair, like walk down the hall. And a physical reset like this helps to clear the buildup a little bit of both the adenosine
which is implicated in tiredness, but also other metabolic byproducts that are associated with some of these concerns. So plan a movement break. Don’t wait for the client to say that they’re tired or need a break. We’ve certainly had a lot of adults who just want to power through. And I’m always kind of amazed at these folks. And they don’t take breaks. They don’t drink water. They don’t go to the bathroom. They don’t eat. And research would say that that is probably not the best way to go about things.
Dr. Jeremy Sharp (09:11)
All right, speaking of eating, the last point is going to center around glycemic management. OK, so many of you probably know that the brain is just like a complete glucose hog. So it consumes probably 20 % of the body’s energy at any given time. And as I talked about at the beginning, cognitive processing requires a lot of effort. So executive functions are
particularly sensitive to drop some blood sugar. So instead of doing like a single big lunch where, you know, the person just takes a lunch break, goes and eats a lot and then comes back in the afternoon, that can lead to that thing that many of us have experienced, which is feeling sleepy in the afternoon. It’s like the food coma, you know, this happens to me quite often. Try to do like small, low glycemic snacks throughout the day.
providing like a handful of nuts, piece of fruit. You can map this onto those 60, 90, or 120 minute breaks. I think that’s great overlap and kind of synchronicity that you can shoot for. Take breaks, eat snacks, drink water. providing these things can biologically kind of re-up the fuel that is needed to maintain this metabolically taxing activity that we call testing.
And I can just say for us, you know, this was a big unlock, I suppose, from a few years ago when we, you know, just decided to stock like almost a whole separate pantry just for client snacks. And yes, it’s an expense. Yes, it’s hard to master dietary constraints and whatnot, but it’s totally worth it, you know? So for one, we have a lot of people who show up without snacks.
Dr. Jeremy Sharp (10:52)
either by choice or by forgetting. We also have a lot of kids who show up kind of underfed and you know having good kind of healthy low glycemic snacks on board and available just goes a long way for many reasons but not the least of which is to help maintain metabolic energy you know just for the testing that we’re doing. So I’m to start to wrap up here.
Just to recap, know, testing fatigue, you know, is not just a nuisance for us, but it is actually a threat to the validity of our data. And there have been many times over the years where I’ve questioned and my employees and supervisees have questioned, hey, is this data actually valid? You know, this kid seemed exceptionally tired and you’re not imagining that. So by just kind of understanding, again, basic understanding of the…
Dr. Jeremy Sharp (11:39)
metabolic costs in the prefrontal cortex and implementing some of these strategies that I just mentioned. I think that can go a long way toward, yeah, combating what we are seeing as fatigue during testing day. So we are going to continue to maintain this one day testing protocol. It just works well, you know, for our practice for many reasons, practically, logistically, clinically. But
implementing some of these strategies if you’re doing longer testing days can go a long way to making sure that you’re ensuring optimal effort. Okay, like I said today was the first episode in this sprint for the rest of the month. Tomorrow we’re going to stay in the clinical pillar and we’re going to be talking about something that a lot of us have heard of but we haven’t actually discussed on the podcast before. So this will be a little bit of an intro slash exploration of
Adult ADHD versus concepts like sluggish cognitive tempo and cognitive disengagement syndrome, which is the newer construct to explore in this realm. Hope to see you then. And again, if you have not liked or subscribed or followed, if it’s Spotify, please do so and you’ll get all these episodes downloaded automatically. Thanks for being here.
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