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21. Somatosensory Processing and Praxis

Here is the journal article Tracy referred to in this episode the direct link and the PDF is attached here as well: https://www.nature.com/articles/s41586-023-05964-2



s41586-023-05964-2
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See our Full Transcript Below:

Cory Dundon: All righty, I wanted to shout out to some listeners who have been sending us questions, we love that. And, um, we appreciate people getting, getting involved and being interested and wanting to learn. We'll do our best to come around to those questions, um, as we're able. We talked about, well, we tried not to talk about Praxis in the last episode.

Uh, we did kind of get there in the end, but we thought maybe this was a nice opportunity for us to just revisit that on purpose this time. Um, and funny enough, after our last episode, I was listening to, uh, Lex Friedman's podcast, with, I've gotta check his name.

Robert Plater, hope that's how, how you say it. the Boston Dynamics, CEO or trying to do the humanoid robot stuff. And they were talking about trying to make robots do. the things that humans can do, and the whole time I was like, this is Praxis. You're trying to replicate Praxis.

And they were, they're coming a long way, like good on them, but it just, if you wanted to understand how hard. or how amazing really, and how integrated Praxis is. Go and listen to them talk about trying to get robots to do, pick things up and throw them and do back flips and walk along surfaces.

Um, I, I might get the quote wrong, but he said something like, The loose rock is like the death of a robot or something like that, because they just can't, um, deal with those sort of unexpected things in their environments and rapidly adapt. Although maybe they're getting a lot better at that.

It would be fun to, to ask him to come on, get a little more information about, maybe be able to, uh, offer some ideas around how they could get better. Um, I'd love to have a little robot dog that could. Do fun things, with me. Um, anyway, so I guess that kind of also moves me towards the somatosensory base dyspraxia.

We did talk about the other clusters, but I was thinking about a little kiddo that I had a while back now. Um, and I was observing him. In childcare in, in preschool I guess. And I was just in the room at the time and he happened to bumble along and, and sort of bop his head, on the corner of a, like a table, I guess It wasn't a bad one, but he kind of hit his eyebrow and.

He got a bit stunned and looked at me and then rubbed the other eyebrow. and I was like, if that's not the clearest sign of a lack of clarity around my body and the input coming in and where was that? then I don't know what is, and it was

such a clear observation, I could go to the educator, like, did you see how he just rubbed the opposite eye to the one that he bumped? And she was like, oh, well that's weird. Like she, and they'd not noticed it before. You know, it's not always that in your face. So maybe we could just chat more about, about the somatosensory basis to this cluster, and firm that up in everyone's minds before we, move on to something else.

Tracy Stackhouse: Yeah, so somato dyspraxia, right? It's a body based dyspraxia and it, it's really, Dr. Ayres did so much research to really, bring to the very forefront how our ability to have detailed, clear body schema and body map is what sets the scene for the exquisite skilled capacity of praxis. So when we are working with children who have these difficulties in the clinic, and you see how off they can be in understanding the signals of their body and it is that's telling them about the front of space, the back of space, the left and right of space. Um,

know, if you can't tell, your, literally cannot tell your elbow from your hand, trying to learn how to color with a crayon. is a humongous task. It, it isn't,

a coincidence that many of the kids that we work with that have functional daily concerns around, I can't tie my shoes, know, my fingers don't do that work Um, and when we look at them through this lens, we learn that their tactile discrimination, their somatosensory awareness, their kinesthetic processing are all super undernourished not working well. And it isn't an under response. It, it's really just that that body map isn't rich enough.

Cory Dundon: Hmm.

Tracy Stackhouse: information processed from receptor into the parietal lobes, into the cerebellum, into the haptic processing. All of that is weak. and Dr Ayres really elucidated this. And then when you see it in the clinic and you realize that, you know, learning how to walk on wobbly rocks is not just practicing walking on wobbly rocks, that you really have to

Michelle Maunder: Hmm.

Tracy Stackhouse: the nervous system to integrate the experience of sensation of. Somatic sensation of movement of vision. And you have to have a lot of enhanced experiences that allow for that map to become, um, dynamic and solidified in the same breath. So it's not static and it's not just dynamic, it's the combination and that map, you know, the homunculus, this is kind of cool.

homunculus was recently updated. and we'll put the link in the show notes for the updated research on this, but it was just this year updated to say that the homunculus as, as we've always seen, that just that body map has to be understood for what happens when there's movement because the purpose. of Somatic sensory Processing. The purpose of sensory integrative processing is always for production of a skill, particularly in the praxis circuitry. Our body map literally has to be dynamic

It has to understand what happens when my foot. Moves across the surface and it's no longer in one spot, but maybe twisted a little bit in one direction or another. And how does that change my body map? If that upsets the apple cart, I'm going to fall down. If the brain map gets scattered by movement itself, by the experience of using the sensation, wow, it becomes super complicated. So it's a really. Powerful thing for us as OTs have the theory from errors to say that the sensory systems in discrimination. Leading into perceptual functions, lay the foundation for skilfulness, and as we treat across that pathway, those pathways where we're drawing from sensation, into skill understanding the dynamics that are at play. Wow.

so much to unpack to observe, so much to treatment plan around. And progress made by treating the whole, not by practicing the end products. that's a really, really critical concept that we need every OT certainly to understand.

Cory Dundon: Mm. I'm trying to visualize this concept that you talked about of the input from the sensors, particularly the Somatosensors,

so I guess if we are talking about the wobbly rock situation, the feedback from, the tactile input underneath my foot and then the proprioceptive signals in the joint of the ankle and maybe like all the joints of my foot, even, um, to know that I'm sort of on something round and then now know that that's shifted underneath me.

So I'm getting that detection. If I haven't had ankle injuries, uh, that have loosened my ligaments and made me poorly able to perceive that, I get that signal into, up into my brain. Into the homunculus, but I'm curious around, oh, it's so funny cuz I just always felt like the homunculus was static.

because you get seen, you get shown it in a picture. It feels static in that way. But I'm trying to understand how, so say the part of my homunculus that detects the information from. Foot, ankle lands in my homunculus in a reasonably similar way.

So that, information's come from that specific body part

Tracy Stackhouse: Mm-hmm.

Cory Dundon: does, is there like a set of neurons that related to, that's really dedicated to that part of my body and if it's in one position, kind of fires a certain way and if it's in another, it kind of shifts to the neurons around it.

So we have this dynamic information about our foot or like, is that just getting, do we just not know that precisely? Or how do I, how do I make sense of the homunculus being this dynamic thing around movement?

Tracy Stackhouse: Yeah. So I think what I love about this update, um, that it, it sort of addresses that question in a way that defies, the standard way we're taught, which is that we're taught that these things happen in a linear process, we know from dynamic systems theory that the linear process is never a linear process,

Cory Dundon: Mm-hmm.

Tracy Stackhouse: but we often think about feed forward and feedback as being, sort of things that are separated from each other. And what you're describing is really the interplay between those, right? So if you are stepping on a surface and you're walking the feed forward, momentum of gait and, and the timing of walking would have you placing your lower extremity in a certain way out in space and continuing that pattern and the feedback of something changed would modify the feed forward. But really what we understand is that the feed forward is waiting for the feedback and the feedback is waiting for the feed forward. So those two things are actually happening, simultaneously, not sequentially. And that is kind of, mind boggling sometimes because we are taught that it's feed forward and feedback.

Cory Dundon: So, this happening centrally, like in the brain or is it happening peripherally, like I'm just, I'm trying to imagine how like, and I know the brain's so complicated that sometimes I just can't get my head around it. But I'm, I'm trying to imagine that in my brain I've like, okay, well then the feedback system has like this set of neurons over here and the feed forward system, as he said, of neurons over here.

And maybe they just like intercommunicate all the time, the whole way up and down the chain. But then I'm like, I just don't. I'm not picturing, I don't really understand, you know, like how that actually works. Um, so is it in the actual brain that this process is happening, that there's just this constant communication between what am I doing?

What have I done? What have I doing, what have I done? Or is it like, how does that work?

Tracy Stackhouse: Yeah, so it is more central in the learning process, in the developmental process, it's more in the central nervous system, but because the peripheral receptors are also learning in the neural network, once you. Know that, when I'm running, and I need to stop quickly that I need to recruit the strength and the tension of the front of my foot versus the back of my foot, and then the receptors in those fields actually start to change because richer receptor beds for pressure of a certain type. And so the whole thing does change Neurodevelopmentally so that eventually it is partly peripheral, but it's mostly central.

Cory Dundon: think I get what you're saying because you are, what you're saying is that as I'm doing one thing, my brain might be preparing for the next that I'm going to do. That might be a change, and in that preparing process, it readily activates, kind of like preemptively gets the body ready, so might be, already firing up the hamstrings or the whatever that I need to recruit to then do the change part. Is that what you mean?

Tracy Stackhouse: Yeah, that's exactly right.

Michelle Maunder: Is that the collary? There's something like random words pop in my head as you talked about that. Is there some collary, is there a mechanism that allows that to happen that you get more, readiness of the receptors and neurons around that in anticipation to get going, which is that get ready front of foot to stop quickly? Is

Tracy Stackhouse: Yeah, absolutely. Absolutely. Yeah. So that sort of corollary discharge is part of it. And then, in the central nervous system. Yeah, there's this kind of heavy in learning process, this active learning process of recruiting, recruiting, recruiting, the expected connectivity. This neuron and this neuron start to work together. You know that neurons that fire together, wire together kind of mantra that we know of back from the 2000's, but it's really literally true that there's this anticipation that that's gonna happen. so what happens for the robots or for us as we're walking on rocky surfaces that are unexpected is that we don't do that all the time, and so we have to slow the whole processing down. We have to start to rely more on a stronger feed forward circuit, so in that, the sensitization of the peripheral receptors gets asked to be more sensitive. Like, I need a little bit more information here, so come on. And so that field of receptors that are sitting on my footbed gets sensitized because my brain needs more information. Um,

Cory Dundon: Happens really rapidly, I guess.

Tracy Stackhouse: yeah, that happens very, very rapidly.

Cory Dundon: yeah. what it made me think of, maybe this is a bit of a random. Link, but it made me think of Michelle, you know, when we did that eye movement, we just did that study in our Bring your own Brain study group, on

Michelle Maunder: Yes.

Cory Dundon: control movement. And it was a, a paper that you had told us to look at Tracy and I cannot remember the name of it, but it was really fascinating I guess they found that pre-emptively the eye, like when you an, you are thinking about moving the eye over to a new spot, your brain's already preparing to see the visual input in that new spot that, that you haven't even put your eye over into that place yet, but it's like already lighting up the visual receptors in that specific, like all the, I guess the rods and the cones that are taking in the information from that visual place in my environment, they're like already starting to prepare for that next thing that I'm gonna look at. And, uh, that, that's, I guess it's again that where am I and what am I going to do?

And then preparing and responding. And. into those two things. I don't know that that made me think about that. Michelle.

Michelle Maunder: And then it makes me wonder we've talked about these before, but the pulling in the partners, cuz as soon as I'm walking on a surface like cement path for example, it's automatic. I'm talking to my partner, you know, blah, blah, blah, blah, blah. And then I get to, if my vision field hasn't caught it already, suddenly walk on uneven ground, so let's keep with the pebble, um, idea, that information from, somatosensory input will. Kind of not add up. So then I'll draw on vision. And my first thing is like, oh, vision, but also because my pace is changing the vestib system's also like, oh, we are accelerating and we are not. And then there's a disturbance, like, you know, polyvagal theory, let's pull that in too.

Then there's a, oh, what is that?

You know, and there's a stilling and I, I can see so many little kids. It's kind of cruel, but you know, when you're at the beach or somewhere or grass and you see the toddlers walking on it, and often it's for the first time and there's that stilling and the real, like, not startle, but there's a ugh. parents like, come on, play, come out to the water. Or you know, whatever. There's this urging and they've just got this, you know, feedback through their feet. And then even if they're looking at it, it's like, Uh, I just can't make sense of this and I actually can't keep going forward yet. I need, I need to be picked up basically or you know, whatever.

But it's like oh that is where you can just see it,

Tracy Stackhouse: Yeah.

Cory Dundon: Yeah.

Michelle Maunder: cascade,

Tracy Stackhouse: unpack that just a little bit cuz I think this is so interesting and, and, and cool. You know,think about, we're talking about somatic sensation as this kind of perceptual layer that supports skillfulness and how as we need more information, the nervous system can recruit more information. But what you're describing in that situation of here's a little bitty one who's going to walk on sand for the first time, and even with all of the affective queuing around them, that this is fun and interesting and wonderful, the novelty of the touch experience or the proprioceptive uncertainty of that novel experience is so big that even with a lot of positive, affective, fun, you know, kind of wooy kiwi kind of stuff going on, we still can have this baby's modulation circuitry say, my brain is answering the question, is this a good thing or a bad thing? As this is a bad thing. And so the opposite happens where the, the Novel Motor Plan requires that there's a increase in feeding the sensory information so that the baby can figure out how to walk on the uneven surface. But the modulation system is saying, no, no, no.

This is a bad thing, don't let yourself even touch it. So the baby withdraws their feet. They don't wanna be sat down. If they sit down, they're crying or they're begging to be picked up and taken out of the situation. So the modulation system is, is telling the system the opposite? Don't sensitize and tell me more about what's go actually get rid of it. So here we have this interplay between modulation and discrimination processing, it happens all day long to us all the time in novel experiences. If the nervous system gets the signal, this isn't safe, you don't want this, then you are restricted from the information you need to solve the problem of it. And so there is this interplay and we know that we have to treat the modulation issue in order to clear the slate for that discrimination to even become relevant and meaningful.

Cory Dundon: Yeah. And then as we treat the discrimination element, that helps the modulation component.

Tracy Stackhouse: That's right.

Michelle Maunder: And in that example trace, if the, babe does kind of still and then is like, oh, give me more information looks tentative. So alarm neurocepted, not safe. But start to work it out, so they might go a lot slower. They might wanna hold hands as they, you know, that increased stability maybe, or maybe it's the co-regulation piece of the hand holding, that they're getting through touch of holding another. I can understand how you went to modulation with that example I gave where they really stopped and then had that negative, emotion. When they're tentative, it's h, I don't wanna pick apart that example, but when they're tentative but still moving forward with support, their own sensory system support, that's probably co-regulation from another and breaking it down a bit, does it sit a bit more in that discrimination rather than the modulation

piece?

Tracy Stackhouse: It absolutely does. And so, what happens in that situation is that as the baby ventures forward, even tentatively. The input that's coming from the tactile and proprioceptive system primarily. So we're talking about somatic sensation. Obviously there is visual and auditory and vestibular partner going on, but if we think about the somatosensory experience, what happens is something really important. And that is that the venturing forward. Does feed information into the system about here's where you are at, here's where you are at, and as long as the baby is like, I kind of got that, okay, I know where I'm at, but I'm a little tentative. But every time they have that

input of Here's where you're at, actually spreading activation. of the homunculus of enriching of that body map. simultaneous to that, the nervous system draws the somatosensory information, not just for the homunculus, not just for this spreading activation of, here's where I'm at, I'm understanding this shifting sand under my foot. I'm gonna do it again. I'm getting it, I'm getting it.

But really importantly, the nervous system also draws that somatosensory information to create inhibition, to say, you don't need to leave. You want to venture forward. You don't need to leave. you need to venture forward because the baby's in engagement and the modulation circuitry is waiting for that inhibitory cue. And the somatosensory system is the primary inhibitory system, so it brings on board the inhibition that allows the tentativeness to turn into, I'm okay to then turn into, I wanna play. And so you see that just unfold right before your eyes. And it is the magic and the power of the somatosensory system to cue us around safety. To then cue us and woo us into participation and engagement to then enrich the map and give us all of the possible affordances, and then to give us the inhibitory control to become really exquisitely skillful. So the whole thing is somatosensory dependent. It's, it's quite incredible.

mm-hmm.

Michelle Maunder: Tracy, you've spoken to me before around the valence and this tipping, like, is that part of this as well? That's somatosensory system. The, the part where they go, oh, here I am, keep moving forward versus get me outta here is that the valence, whether it tips or whether it wobbles and they co-regulate it or get more information and so, you know, do things to slow it down, that keeps them adaptive and engaged versus the valence tips and it's all over red rover.

Tracy Stackhouse: That's precisely it. Yep. That's spot on.

Cory Dundon: I,

I thought about Michelle, you brought in the polyvagal stuff around this whole process cuz in the moment that they're tentative, there's that slight sympathetic,

Michelle Maunder: Mm-hmm.

Cory Dundon: Activation the input is signaling potentially maybe unsafe. And then you get that slight, partial freeze or just stilling and like orienting.

And then like with, with Audrey, she'll look at me and kind of go like, what the heck? And um, and you are right. Like I can use my social engagement circuitry for her to go, oh, feels funny. Like, oh, funny on your feet. And then she's like, Yeah, it kind of does feel funny like, but it takes a little bit but I can use, because that, a capacity that she can draw off of. She can then use that to modulate or inhibit. The

modulation circuitry. Yeah. Yeah. And then

and then do the approach, I guess, to then refine the somatosensory input of what is this grass or sand or thing that I've got my feet in.

Michelle Maunder: So just going back to that valence and the tipping and that, so that, which I love that you said the stilling, so there's a pause and that's where the body can, if we get a co-regulator to go. Yeah, yeah. Hang in there. Don't fire off and tip off into, real mobilization.

And, um, that's that point where it's wobbly, that you've got an ability to just hold them where they're at, co-regulate it, and the valence goes, oh. Okay. Mom thinks it's okay and I trust her. She's reliable. It's weird. Mom, if you wanna call it funny, I call it like, what the hell? not just, what the heck?

It's like bigger than that.

Cory Dundon: Depends on your response, I guess,

how much it was like.

Michelle Maunder: Yeah, but I think that's the, I think that's a bit where it's like you, there was a pausing, a stilling you signal safety. Yeah, it's okay babe. It is funny. Um, and then she had then capacity, I guess, to dampen down her arousal, which allowed inhibition to happen.

Ugh, did

Cory Dundon: Yeah, in my mind it's, again, trying to, Keep in mind the fact that the social engagement circuitry of the ventral vagal capacity must have such deep, intricate links to the modulation of Somato sensation. and so somatosensory input to me has to be delivered in the context of ventral vagal state, for curiosity and exploration for skill development.

Tracy Stackhouse: That's right. And in the context of co-regulation,

Cory Dundon: Yeah.

Tracy Stackhouse: the way that the co-regulatory experience, whether or not we think about that through an attachment lens or just through the polyvagal system, you invoke this, quieting this kind of like as soon as you get that pause and you get a reference to, I need the other to help me through this experience. and some of our kids offer that signal so quickly and so elusively that we don't always pick up on it, and then nervous system gets really confused. What am I supposed to do here? I was looking for that partner. I was looking for the person, partner, I was looking for an environmental partner. I was looking for my brain partner to give me the queuing, the signaling or the extra reassurance that I need, whether that be through enhanced proprioception or enhanced mom energy, whatever that is,

Michelle Maunder: Hmm.

Tracy Stackhouse: allows me to re story the, uh, oh. To a, oh curious. To a, oh, maybe, you know, we're kind of moving them through this emotional, affective, sensory motor experience and as we move them through that, kids create adaptation. When they don't get what they need. The adaptive response is constrained and limited, and then the next opportunity is repeated with more trepidation, with more error with less efficiency because we're not growing the richness of that network and that's precisely what, happens in the journey for kids who are, where it's coming together.

Well, and, and when it isn't coming so well together. Yeah.


Michelle Maunder: mm. I'm loving watching you watch Audrey grow with your OT head on, as you know, as Mum because it's happening pretty automatically. Luckily, and we're very grateful for that, um, for Audrey. And you're like, you've sent me some videos that only us could break down frame after frame for 30 seconds of her finding her hands and putting them in midline together, or you know, I think she was trying to get a toy once for a long time, but she stuck with it. It's fascinating. Trace, with your grandchildren, how automatic it can be and that you can just signal, oh, it's funny, isn't it, honey? And then sand becomes an not a thing that you ever really have to think about or, or respond to. In that way, again, it's like, oh, we dealt with sand automatically. Like lots of families wouldn't even know that there may be an issue with a different texture on their feet. Yet, you know, we also are working every day with kiddos where that automatic, that real, something isn't processing well. So it doesn't, that whole experience doesn't sync up in a way that's, automatic for them and integrated in just daily family life that it requires, intervention and really, thoughtful and nuanced, um, and planned out, intervention to support them to get the tactile input

or, the somatosensory intervention that they need. That it, that you can't shortcut it. You can't just take them to


Cory Dundon: Just put them in lots of sand. Yeah. And I think that's partly sometimes the most powerful stuff that we do, right? Is in our observations that aren't your typical day-to-day things people pay attention to is just drawing people's attention to the fact that like, oh, Yeah. I didn't think about that being the sand. I just thought they just didn't wanna do the, the game. I just thought they didn't wanna play, or whatever. Like, It's a really powerful position to shift the perception of it, because it, when you're not purposely trained to look for that moment, you don't really see it. Like pre OT I wouldn't have been, if a kid had stopped on the sand, I wouldn't have necessarily been like, oh, they don't like the sand on their feet. I could have thought it was like a whole bunch of different things. Why they didn't want to keep going or even, like, I probably wouldn't have even noticed that little kid bumped his eyebrow that he rubbed the other one. Because I'm so always looking for the clues from the systems. Where the breakdown might be that's where I love to share with families, like my observations around that. And then families just like take it and run with it. Once they start to see it, they see it, they really see it, and they know it, and then they can, they can get it.

And then really makes a more powerful change than, than, just me doing it, I love that as part of our job, like how we can have some benefit in that way.


Tracy Stackhouse: Yeah, absolutely. Yeah. That dawning awareness that we see in the parent the same. Same thing that's happening to the baby when they suddenly can feel their feet, and they couldn't before and so all walking was trepidatious, let alone on sand or rocky surfaces. Because if you don't have strong awareness of your body in space, how are you supposed to move? And then when you start to make sense of it, and it becomes available to you. The affordance is now changed and I can feel my feet and I do know that they can move and I do know they can weight bear and I do know all of those things. So, we work with kids with all different levels and layers and layers and layers of profound restrictions sometimes. And as you open the possibility of my feet are walkable. It's so profound what happens and then for these kiddos where it's more of a restriction of sand is scary and yucky, but now sand is fun. That shift, that growing awareness. So, you know, learning to discipline your observations through the lens of modulation, through the lens of discrimination, is the crux of powerful intervention. And then from there we have to layer in a lot of other knowing about, the motor processes that are involved in Praxis, the executive functioning processes that are involved in Praxis, But it starts at this sensory level and we always have to separate the modulation from the discrimination for our clinical reasoning to be effective and so I really appreciate how you both are doing that, and you're exercising those thinking muscles all the time and, now you're sharing that with everybody, so it's powerful.


Cory Dundon: I appreciate that. Thank you, Tracy. Uh, that's just, you know, that you've had a powerful impact on my ability to do that, so thank you right back. But, um, the thing that I was thinking about when you were talking about all the different things that you have to have in your knowing as a clinician around Praxis, it made me think about like if you are starting to do the understanding and observing this dance of the modulation/discrimination functions, and then maybe you're at a higher level kiddo, that's then I guess that's able to use their cognition. And how we do this dance between this underlying process and making sure that that's kind of we're aware of that and we are harnessing the how, how we approach that in treatment. We're catching the opportunities to keep the modulation system at bay and whether that's, like you said, through enhanced proprioceptive feedback, whether it's timing, giving them more processing information, allowing respecting the response their nervous system has and then creating the opportunities to restore it and have control over their approach a bit more. Or you know how, however it is, maybe we're grading it, whatever that part is that we're, I guess, intervening around that space. Then the other part that came to mind for me was the, the kiddos that do have the cognition and then also the executive function systems that.

We utilize often, and I used to do it way too much as a new clinician was just like trying to reason with the cortex around praxis or, you know, and, and some kiddos do have they're really intelligent and they do almost really over rely on the cortex in that regard. But maybe that's something we could talk about next time is the executive function components that relate to the Praxis circuitry and the interventions, how we can make them look more holistic, I guess, to take into account both parts.


Tracy Stackhouse: I love that. That's sounds like the next good episode. I look forward to that for sure.

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