In the podcast released yesterday, Walter Bradley Center director Robert J. Marks interviewed pediatric neurologist Dr. Andrew Knox from the University of Wisconsin School of Medicine and Public Health on “Ways the brain can break” (#220, January 5, 2023).
What follows reflects Part 2 of the discussion. Here’s Part 1: How our brains are — and aren’t — like computers.
This portion begins at roughly 10:50 min. A partial transcript and notes, and Additional Resources follow.
Andrew Knox: If you had a stroke in what we would call a primary motor area, an area with the connections to motor pathways through the rest of the body — all of those patients might lose the ability to move their arm on one side of the body, or their leg, or their face, or all three of those things.
Robert J. Marks: Now, some of those things I think people can recover from. I’ve heard the word neuroplasticity. It’s kind of like if part of the brain fails, then another part of the brain takes over. I’m sure that there’s cases where you can’t cure it, but there are cases where you can. Does neuroplasticity play a role in that?
Andrew Knox: Yeah, it absolutely does. There actually aren’t too many areas where — if you have an injury to that part of the brain — you can’t have other parts of the brain take take over.
Andrew Knox: There are a few special areas. Areas involved with language, to some extent, are less plastic. Visual pathways are sort of hard-coded into the brain, so [for] strokes in primary visual areas, you wouldn’t expect to recover normal vision after that. Similar for primary motor areas. Usually, if you have a stroke in a primary motor area, you would expect to sort of have long-term motor deficits.
Robert J. Marks: Motor area? You mean things that just affect how you move your arms and legs, and things of that sort?
Andrew Knox: Yep. Those are sort of the big three. There are some sensory areas that are the same way. If you have a stroke in a primary sensory area, you might always have problems sensing or feeling sensation in your right hand, or your right leg, or something like that. But again, those are the specific exceptions to the more general rule that the brain is good at moving function between different areas.
Robert J. Marks: That’s just, to me, astonishing. I’ve seen blind people, for example, that aren’t using the neurons that they were supposed to use for sight, and they’ve developed the capability of going into a room and just clicking, and hearing the echo like a bat, and actually “seeing” — through the echo — their environment,. I think some of the other things that you’re talking about are a little bit more subtle. You see the recovery, but they’re not as in-your-face as the clicking.
Note: Dr. Marks is referring to the human use of echolocation, a skill highly developed in bats but largely ignored by sighted humans. Some blind humans have developed it as a skill. See, for example, “There really is a Batman and he isn’t in the comics.”
Andrew Knox: I would say that’s a different sort of way of coping. They haven’t regained an ability that they had before, but they’ve developed a different set of abilities. If you lose the sense of vision, your sense of hearing may become more acute, it may become better, You may develop ways to use that to sort of replace that other function. But I was actually talking more about recovering a function you had before. So if you have a stroke in the left motor area and you for a while can’t move your right hand, even after six months, you can have some recovery of that function — even though those neurons aren’t growing back. That’s because there are connections from the other side of the brain to that hand as well. So those connections may become stronger, and you may be able to use them better.
Robert J. Marks: I see. So there is a difference between adapting for something you haven’t had since birth, and then adapting from a function that you’ve lost through, for example, a stroke?
Andrew Knox: I would make a distinction between adapting for loss of a function by developing a new function that you wouldn’t have developed otherwise, versus the brain adapting to recover a function that you’ve lost — that same function.
Hedder: Neuroplaticity and strokes, dementia in children
Robert J. Marks: Now, strokes in kids, what’s the primary cause of that? Is it something which is genetic? Is it something that’s happened to them an accident?
Andrew Knox: It’s a spectrum of things. Infections can actually be a common cause, or an immune response to an infection. Clotting disorders can be a common cause. There’s a disease called sickle cell disease, which can be a common cause for stroke in kids.
Actually, there are a number of kids now who have substantial heart malformations or congenital cardiac problems. Forty years ago, many of those kids would’ve just died very early in life. Now, they can actually live relatively full lives. One consequence of their cardiac disease is they’re more prone to developing clots, and that sort of thing, which can be a cause for stroke. So they’re a patient population where we see strokes in kids a little more often…
Robert J. Marks: One of the ways you mentioned that brains can break is dementia, and I always associate dementia with old age, but can kids have dementia?
Andrew Knox: There are some disorders where kids can have dementia. Dementia is a little different from strokes. Strokes, the idea is you have an injury to a particular part of the brain, and then you wind up losing the function that goes with that particular area of the brain. Dementia, usually, you have a problem that affects the whole brain at the same time, or at least the brain more diffusely. So it’s not one particular area of the brain; it’s the brain as a whole. You don’t lose all of the neurons in the brain at the same time, but you start to progressively have injury to more and more neurons throughout the whole brain. That causes a different sort of change, where you see loss of cognitive function over time.
Robert J. Marks: So you can say that dementia is kind of distributed, whereas stroke are localized?
Andrew Knox: Right, and less focal. Now, there are exceptions to everything in neurology, but I think that’s a good way to think about dementia. Kids can have sometimes particular genetic [problems] or problems with cellular processes that lead to something like dementia. In adults, it’s much more likely to be a part of the natural aging process. In children, usually it would take a specific disorder that they have that would cause earlier onset dementia.
Note: One cause of childhood dementia is a rare genetic disorder called Batten disease.
Robert J. Marks: So it is something which is gradual, then?
Andrew Knox: It is gradual. You see the effects of the stroke over minutes to hours. Dementia, usually, you think of seeing the effects over months to years.
And adults, again, don’t necessarily lose one particular function on one side of the body, but you see the effects of that sort of diffuse loss of neurons. You see that with more global cognitive functions, so problems paying attention to things, problems with memory, problems with just understanding the world around you. Some of those symptoms can follow really interesting progressions that maybe give some insights into how brains work.
Next: How do strokes, dementia offer insight into how the brain works?
You may also wish to read: Part 1: How our brains are — and aren’t — like computers. Pediatric neurologist Andrew Knox looks at the topic with computer engineer Robert J. Marks. The conversation drifts to strokes — one of the ways that the brain can “break,” even in children.
Part 3: How do strokes, dementia offer insight into how the brain works? Neurologist Andrew Knox thinks the brain may store memories is an associative scheme, where previous memories are used to build up new ones. Some episodes of loss of consciousness are not seizures or stroke; syncope, caused by low blood pressure, can turn out to be harmless.