Last episode we kept dodging praxis. This time we go straight at it, starting with the body-based cluster, somatodyspraxia, and the body map that makes skilled movement possible. Along the way: why a child rubbed the eyebrow he did not bump, why robots still fall over on a loose rock, and why feedforward and feedback are not a sequence but a conversation happening all at once.
We set out last episode trying not to talk about praxis, so this time we did it on purpose. We start with somatodyspraxia, the body-based dyspraxia, and the clear, almost startling signs of it, like the little one Cory watched bump one eyebrow and rub the other. From there Tracy takes us into the body map, the recently updated homunculus, and the idea that it is not a static picture at all but a dynamic thing that has to keep up with movement.
We spend real time on feedforward and feedback, which it turns out are not a tidy sequence but two processes waiting on each other at once, and then on the part that matters most clinically: how modulation and discrimination interweave, why the somatosensory system is the primary inhibitory system, and how a co-regulator holds a child at the wobbly, tipping point of a new experience until curiosity can win. There are toddlers meeting sand for the first time, a baby learning on the grass, and a reminder that often our most powerful intervention is simply noticing what no one else was trained to see.
Lightly edited for readability. Speaker labels and chapter markers match the published episode.
Cory: All righty. I wanted to shout out to some listeners who have been sending us questions. We love that, and we appreciate people getting involved and wanting to learn. We will do our best to come around to those questions as we are able. Last episode we tried not to talk about praxis, and we did kind of get there in the end, but we thought this was a nice opportunity to revisit it on purpose this time. Funny enough, after our last episode I was listening to the Lex Fridman Podcast with, I have to check his name, Robert Playter, I hope that is right, the CEO of Boston Dynamics, who are doing the humanoid robot work. They were talking about trying to make robots do the things humans can do, and the whole time I was thinking, this is praxis, you are trying to replicate praxis. They are coming a long way, good on them, but if you want to understand how hard, or really how amazing and how integrated praxis is, go and listen to them talk about trying to get robots to pick things up, throw them, do backflips, and walk along surfaces. I might get the quote wrong, but he said something like, the loose rock is the death of a robot, because they cannot deal with those unexpected things in their environment and rapidly adapt. Although maybe they are getting a lot better at that. It would be fun to ask him to come on. I would love a little robot dog that could do fun things with me. Anyway, that moves me towards somatosensory-based dyspraxia.
Cory: We did talk about the other clusters last time, but I was thinking about a little kiddo I had a while back. I was observing him in childcare, in preschool, just in the room at the time, and he bumbled along and bopped his head on the corner of a table. It was not a bad one, he hit his eyebrow, got a bit stunned, looked at me, and then rubbed the other eyebrow. And I thought, if that is not the clearest sign of a lack of clarity about my body and where the input is coming from, I do not know what is. It was such a clear observation that I could say to the educator, did you see how he rubbed the opposite eye to the one he bumped? And she said, oh, that is weird, they had not noticed it before. It is not always that in your face. So maybe we could chat more about the somatosensory basis to this cluster and firm it up in everyone’s minds before we move on.
Tracy: So, somatodyspraxia. It is a body-based dyspraxia, and Dr Ayres did so much research to bring to the forefront how our ability to have a detailed, clear body schema and body map is what sets the scene for the exquisite, skilled capacity of praxis. When you work with children who have these difficulties and see how off they can be in understanding the signals of their body, the front of space, the back of space, the left and right, you realise that if you literally cannot tell your elbow from your hand, learning to colour with a crayon is a humongous task. It is no coincidence that many of the kids we work with have daily concerns like, I cannot tie my shoes, my fingers do not do that work. When we look at them through this lens, we learn that their tactile discrimination, their somatosensory awareness, their kinaesthetic processing are all undernourished and not working well. It is not an under-response, it is that the body map is not rich enough. The 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. When you see it in the clinic, you realise that learning to walk on wobbly rocks is not just practising walking on wobbly rocks. You have to help the nervous system integrate the experience of somatic sensation, of movement, of vision, and you need a lot of enhanced experiences that allow that map to become dynamic and solidified in the same breath. So it is not static, and it is not just dynamic, it is the combination.
Tracy: The homunculus was recently updated, and we will put the link in the show notes. It was just updated to say that the body map has to be understood for what happens when there is movement, because the purpose of somatosensory processing, of sensory integrative processing, is always the 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 a surface and is no longer in one spot but maybe twisted a little in one direction or another, and how that changes my body map. If that upsets the apple cart, I fall down. If the brain map gets scattered by movement itself, by the experience of using the sensation, it becomes super complicated. So it is a powerful thing for us as OTs to have the theory from Ayres, that the sensory systems, through discrimination leading into perceptual functions, lay the foundation for skilfulness, and as we treat across those pathways, drawing from sensation into skill, we have to understand the dynamics at play. There is so much to observe, so much to plan treatment around. And progress is made by treating the whole, not by practising the end products. That is a really critical concept that we need every OT to understand.
Cory: I am trying to visualise this concept of the input from the sensors, particularly the somatosensors. If we are talking about the wobbly rock, the feedback from the tactile input under my foot, and the proprioceptive signals in the ankle and all the joints of my foot, tell me I am on something round and then that it has shifted underneath me. If I have not had ankle injuries that loosened my ligaments and made me poorly able to perceive that, I get that signal up into my brain, into the homunculus. But it is funny, I always felt the homunculus was static, because you get shown it in a picture. So say the part of my homunculus that detects information from my foot and ankle lands in roughly the same place. Is there a set of neurons dedicated to that part of my body, and if it is in one position it fires a certain way, and in another it shifts to the neurons around it, so we have dynamic information about our foot? Or do we just not know that precisely? How do I make sense of the homunculus being a dynamic thing around movement?
Tracy: What I love about this update is that it addresses that question in a way that defies the standard way we are taught, which is that these things happen in a linear process. We know from dynamic systems theory that the linear process is never actually linear. We tend to think of feedforward and feedback as separated from each other, but what you are describing is the interplay between them. If you are walking, the feedforward momentum and timing of gait places your lower limb in a certain way in space and continues the pattern, and the feedback of something changing would modify the feedforward. But really, the feedforward is waiting for the feedback and the feedback is waiting for the feedforward. So those two things are happening simultaneously, not sequentially, which is mind-boggling, because we are taught feedforward and then feedback.
Cory: So is this happening centrally, in the brain, or peripherally? I know the brain is so complicated that sometimes I cannot get my head around it, but I am trying to imagine that the feedback system has one set of neurons over here and the feedforward system another, and maybe they intercommunicate all the way up and down the chain. Is it in the actual brain that this constant communication is happening, between what am I doing and what have I done? Or how does that work?
Tracy: It is more central in the learning process, in the developmental process, more in the central nervous system. But because the peripheral receptors are also learning in the neural network, once you know that when I am running and need to stop quickly I have to recruit the strength and tension of the front of my foot versus the back, the receptors in those fields actually start to change, with richer receptor beds for pressure of a certain type. So the whole thing does change neurodevelopmentally, so that eventually it is partly peripheral, but mostly central.
Cory: I think I get what you are saying. As I am doing one thing, my brain might be preparing for the next thing I am going to do, which might be a change, and in that preparing process it preemptively gets the body ready, maybe already firing up the hamstrings, or whatever I need to recruit to do the change part. Is that what you mean?
Tracy: Yes, that is exactly right.
Michelle: Is that the corollary? Random words pop into my head as you talk. Is there a corollary, a mechanism that gives you more readiness of the receptors and the neurons around that, in anticipation, to get going, that get-ready-front-of-foot-to-stop-quickly?
Tracy: Yes, absolutely. That corollary discharge is part of it. And then in the central nervous system there is this heavy, active learning process of recruiting the expected connectivity, this neuron and this neuron starting to work together. You know the mantra, neurons that fire together wire together, from back in the 2000s, but it is literally true that there is this anticipation that it is going to happen. So what happens for the robots, or for us walking on rocky surfaces that are unexpected, is that we do not do that all the time, so we have to slow the whole processing down. We have to rely more on a stronger feedforward circuit, and the sensitisation of the peripheral receptors gets asked to be more sensitive, I need a bit more information here, come on. So that field of receptors on my footbed gets sensitised because my brain needs more information.
Cory: Happens really rapidly, I guess.
Tracy: Yes, that happens very, very rapidly.
Cory: What it made me think of, maybe this is a bit of a random link, but Michelle, you know that eye-movement study we did in our Bring Your Own Brain study group, on eye control, the paper you told us to look at, Tracy. I cannot remember the name of it, but it was fascinating. They found that preemptively, when you are thinking about moving your eye to a new spot, your brain is already preparing to see the visual input in that new spot, before you have even moved your eye there. It is already lighting up the visual receptors, the rods and cones taking in information from that place in your environment, already preparing for the next thing you are going to look at. So again it is that where am I, and what am I going to do, preparing and responding.
Michelle: And it makes me wonder about pulling in the partners. As soon as I am walking on a surface like a cement path, it is automatic, I am chatting to my partner, blah blah blah. Then, if my visual field has not caught it already, I suddenly walk on uneven ground, let’s keep with the pebble idea, and that somatosensory information does not add up. So I draw on vision first, and because my pace is changing the vestibular system is going, oh, we are accelerating, and we are not. Then there is a disturbance, and let’s pull polyvagal in too, there is a, oh, what is that, and a stilling. I can see so many little kids, it is kind of cruel, but when you are at the beach or on grass and you see toddlers walking on it, often for the first time, there is that stilling, not a startle but an ugh, and the parents are urging, come on, come out to the water, play. The child has this feedback through their feet, and even if they are looking at it, it is like, I just cannot make sense of this, I cannot keep going forward yet, I need to be picked up. That is where you can just see it, the cascade.
Tracy: Let me sit with that a little, because it is so interesting. We are talking about somatic sensation as a perceptual layer that supports skilfulness, and how, as we need more information, the nervous system can recruit more. But in that situation of a little one walking on sand for the first time, even with all the affective cueing around them that this is fun and wonderful, the novelty of the touch, or the proprioceptive uncertainty, is so big that even with a lot of positive, fun energy, the baby’s modulation circuitry answers the question, is this a good thing or a bad thing, with, this is a bad thing. So the opposite happens: the novel motor plan needs an increase in feeding the sensory information so 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, do not even touch it. So the baby withdraws their feet, does not want to be sat down, cries, begs to be picked up. The modulation system is telling the system the opposite, do not sensitise and tell me more, actually get rid of it. So here we have this interplay between modulation and discrimination, and it happens all day long in novel experiences. If the nervous system gets the signal this is not safe, you are restricted from the information you need to solve the problem. So we have to treat the modulation issue in order to clear the slate for the discrimination to even become relevant and meaningful.
Cory: And then as we treat the discrimination element, that helps the modulation component.
Tracy: That is right.
Michelle: In that example, Tracy, if the baby stills and then is like, give me more information, looks tentative, so alarm, neurocepted not safe, but they start to work it out, they go slower, maybe they want to hold hands for that increased stability, or maybe it is the co-regulation of the hand-holding, the touch of holding another. I can see why you went to modulation with my example, where they really stopped and had that negative emotion. But when they are tentative and still moving forward with support, their own sensory support or co-regulation from another, does that sit a bit more in discrimination than modulation?
Tracy: It absolutely does. As the baby ventures forward, even tentatively, the input coming primarily from the tactile and proprioceptive system, the somatic sensation, does something really important. The venturing forward feeds information into the system about here is where you are at, here is where you are at, and as long as the baby is, I kind of got that, I know where I am, but I am a little tentative, every time they get that input it is spreading activation of the homunculus, enriching the body map. At the same time, the nervous system draws that somatosensory information not just to enrich the map, but to create inhibition, to say, you do not need to leave, you want to venture forward, you do not need to leave. The baby is in engagement, and the modulation circuitry is waiting for that inhibitory cue. The somatosensory system is the primary inhibitory system, so it brings on the inhibition that lets tentativeness turn into I am okay, and then into I want to play. You see it unfold right before your eyes. It is the magic and the power of the somatosensory system, to cue us around safety, to woo us into participation and engagement, to enrich the map and give us all the affordances, and then to give us the inhibitory control to become exquisitely skilful. The whole thing is somatosensory dependent. It is quite incredible.
Michelle: Tracy, you have spoken to me before about valence and this tipping. Is that part of this too, this somatosensory system, the part where they go, here I am, keep moving forward, versus, get me out of here? Whether the valence tips, or whether it wobbles and they co-regulate it or get more information and slow it down, that keeps them adaptive and engaged, versus the valence tips and it is all over red rover.
Tracy: That is precisely it. Spot on.
Cory: I thought about the polyvagal piece you brought in, Michelle, because in the moment they are tentative there is that slight sympathetic activation, the input is signalling potentially unsafe, and you get that slight partial freeze or stilling and orienting. With Audrey, she will look at me and go, what the heck, and you are right, I can use my social engagement circuitry, oh, feels funny, funny on your feet, and she goes, yeah, it kind of does feel funny. It takes a little bit, but she can draw off that capacity to modulate or inhibit the modulation circuitry, and then do the approach, to refine the somatosensory input of what is this grass or sand I have got my feet in.
Michelle: Going back to the valence and the tipping, and I love that you said the stilling, there is a pause, and that is where, if we get a co-regulator to go, yeah, yeah, hang in there, do not fire off and tip into real mobilisation. At that wobbly point you have the ability to hold them where they are at, co-regulate it, and the valence goes, oh, okay, Mum thinks it is okay and I trust her, she is reliable. It is weird, Mum, if you want to call it funny, I would call it more like what the hell, not just what the heck, it is bigger than that.
Cory: Depends on your response, I guess.
Michelle: Yes, but that is the bit, there was a pausing, a stilling, you signal safety, it is okay babe, it is funny, and then she has the capacity to dampen down her arousal, which allows inhibition to happen.
Cory: In my mind, the social engagement circuitry of the ventral vagal capacity must have such deep, intricate links to the modulation of somatosensation. So somatosensory input has to be delivered in the context of ventral vagal state, for curiosity and exploration and skill development.
Tracy: That is right, and in the context of co-regulation. The co-regulatory experience, whether we think about it through an attachment lens or through the polyvagal system, invokes this quieting. As soon as you get that pause, you get a reference to, I need the other to help me through this. Some of our kids offer that signal so quickly and so elusively that we do not always pick up on it, and then the nervous system gets confused, what am I supposed to do here, I was looking for that partner, the person, the environmental partner, my brain partner, to give me the cueing or the extra reassurance I need, whether through enhanced proprioception or enhanced Mum energy, whatever it is, that lets me re-story the oh into oh, curious, into oh, maybe. We move them through that emotional, affective, sensory-motor experience, and as we do, kids create adaptation. When they do not get what they need, the adaptive response is constrained and limited, and the next opportunity is repeated with more trepidation, more error, less efficiency, because we are not growing the richness of that network. That is exactly what happens in the journey for kids, whether it is coming together well or not.
Michelle: I am loving watching you watch Audrey grow with your OT head on, as well as being her Mum, because it is happening pretty automatically, luckily, and we are grateful for that. You have sent me videos that only we could break down, frame after frame, of 30 seconds of her finding her hands and bringing them to midline together, or sticking with trying to get a toy for a long time. It is fascinating. And Tracy, with your grandchildren, how automatic it can be, where you just signal, oh, it is funny, isn’t it, honey, and then sand becomes a non-issue, something you never really have to think about again. Lots of families would not even know there might be an issue with a different texture on their feet. Yet we work every day with kiddos where that automatic process is not happening well, where it does not sync up in a way that is automatic and integrated into daily family life, and it requires thoughtful, nuanced, planned-out intervention to support them to get the somatosensory input they need. You cannot shortcut it. You cannot just take them to the sand a lot of times and think it will sort itself out.
Cory: Just put them in lots of sand. And that is partly sometimes the most powerful stuff we do, in our observations, the things that are not the typical day-to-day stuff people pay attention to. Just drawing people’s attention to the fact that, oh, I did not think about that being the sand, I just thought they did not want to play. It is a powerful position, to shift the perception of it, because when you are not purposely trained to look for that moment, you do not see it. Pre-OT, if a kid had stopped on the sand, I would not necessarily have thought, oh, they do not like the sand on their feet, I could have thought it was a whole bunch of different things. I probably would not even have noticed that little kid bump his eyebrow and rub the other one, because I am always looking for the clues from the systems, where the breakdown might be. That is what I love to share with families, my observations, and then families take it and run with it. Once they start to see it, they really see it, they know it, and they can get it, and that makes a more powerful change than just me doing it. I love that part of our job.
Tracy: Absolutely. That dawning awareness we see in the parent is the same thing happening to the baby when they suddenly can feel their feet and could not before, so all walking was trepidatious, let alone on sand or rocky surfaces. If you do not have strong awareness of your body in space, how are you supposed to move? When you start to make sense of it and it becomes available to you, the affordance changes, I can feel my feet, I know they can move, I know they can weight bear. We work with kids with layers and layers of profound restriction sometimes, and as you open the possibility of, my feet are walkable, it is so profound what happens. And for the kiddos where it is more a restriction of, sand is scary and yucky, but now sand is fun, that shift, that growing awareness. So learning to discipline your observations through the lens of modulation and the lens of discrimination is the crux of powerful intervention. From there we layer in a lot of other knowing about the motor processes involved in praxis, the executive functioning processes 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. I really appreciate how you both do that, exercising those thinking muscles all the time, and now sharing it with everybody. It is powerful.
Cory: Thank you, Tracy. You have had a powerful impact on my ability to do that, so thank you right back. The thing I was thinking about, when you were talking about all the things you have to hold as a clinician around praxis, is that if you are observing this dance of the modulation and discrimination functions, and then you have a higher-level kiddo who is able to use their cognition, how do we do this dance between the underlying process and harnessing how we approach it in treatment? We catch the opportunities to keep the modulation system at bay, whether through enhanced proprioceptive feedback, or timing, or giving them more processing time, respecting the response their nervous system has and then creating opportunities to restore it and give them more control over their approach, or grading it. The other part that came to mind is the kiddos who do have the cognition and the executive function systems, which we utilise, and which I used to lean on way too much as a new clinician, just trying to reason with the cortex around praxis. Some kids are really intelligent and over-rely on the cortex. Maybe that is something we could talk about next time, the executive function components that relate to the praxis circuitry, and how we make our interventions more holistic to take both parts into account.
Tracy: I love that. That sounds like the next good episode. I look forward to that for sure.
And that’s a wrap on today’s episode of Spirited Conversations. We hope this sparks something for you, whether it’s a new clinical idea, a fresh perspective, or just the reminder that you are definitely not alone in this work. If this conversation resonated, we would love for you to share it with anyone on their own learning journey. You can find information about the podcast on our website, and you can join us in the courses and communities the Developmental FX team have put together at developmentalfx.org. And if you’re enjoying listening, please subscribe or leave a review, it genuinely helps more people find us. Until next time, keep the conversations spirited!