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In Part Two, we looked at the Moro Reflex and the possibility that a retained primitive response may tell us something about how the nervous system responds to sudden change. With the Tonic Labyrinthine Reflex, or TLR, the conversation shifts in a slightly different direction. This time, let’s talk about gravity.

Gravity is something most of us rarely think about. We stand up, bend over, turn our heads, drop our keys, look toward the ceiling, walk across a room, and somehow continue knowing where we are in space. Our eyes continue to provide useful information, our balance adjusts, our posture changes, and our muscles make thousands of small corrections without requiring much conscious thought, but none of that was automatic when we were born. Early in development, the position of the infant’s head relative to gravity has a powerful influence over the rest of the body. The Tonic Labyrinthine Reflex is part of that early relationship. As the nervous system matures, however, the child has to develop something considerably more sophisticated: the ability to move the head without the rest of the body being dictated by that position, and for those of us working in Vision Therapy, that raises an interesting question:

What happens to vision when simply organizing the body against gravity requires more effort than it should?

What Is the Tonic Labyrinthine Reflex?

The TLR is a primitive response involving changes in muscle tone associated with the position of the head relative to gravity. It is generally discussed in two directions: flexion and extension.

In flexion, movement of the head forward tends to increase flexor influence through the body. In extension, moving the head backward tends to increase extensor influence.

Let’s consider what that means for an infant. The newborn is entering a world in which gravity is now a constant demand. The nervous system has to learn where the head is, where the body is, and eventually how to organize movement against gravity. Early reflexive responses provide a temporary framework while more sophisticated postural systems develop, but eventually, something important has to happen. The head needs to become increasingly independent from the body. A child needs to be able to look down without the entire body wanting to flex, they need to look up without the body being pulled toward extension, they need to move the head while maintaining balance, posture, and control of the limbs. In other words, the position of the head can no longer be allowed to dictate what the rest of the body does. As voluntary head control, postural reactions, balance, and more mature sensory-motor systems develop, the influence of the TLR should become increasingly inhibited and regulated.

And once again, the word regulated is crucially important.

As we discussed with Moro, saying that a Primitive Reflex becomes “integrated” can make it sound as though the neurological circuitry simply disappears. A more useful way to think about it may be that higher neurological systems increasingly regulate primitive responses as more sophisticated postural and voluntary control develops. Best stated, the nervous system develops better options.

TLR and Our Relationship With Gravity

TLR is particularly interesting because gravity never goes away. From the moment we get out of bed in the morning, the nervous system is continuously solving a postural problem. Where is my head? Where is my body? Am I upright? Am I moving? Which muscles need to activate? How much tone is necessary? Where is the floor? Which way is vertical?

Most of us answer those questions without ever consciously asking them. That ability depends upon cooperation among several systems. Vestibular information helps tell us about head movement and orientation. Proprioceptive information tells us about the position of our muscles and joints. Vision provides an enormous amount of information about where we are relative to the environment. Postural and motor systems use that information to keep us upright and allow us to move efficiently.

The developing infant doesn’t begin with that level of organization. They have to build it. That is what makes TLR so interesting. It sits near the beginning of a developmental process that eventually allows the head, eyes, and body to work together without being completely dependent upon one another.

The Physical Side of a Retained TLR

If the influence of TLR remains unusually active beyond the period when we would expect increasingly mature postural control, the most obvious place we might see the consequences is physically. But once again, we want to be careful about what we claim. A retained TLR does not explain poor posture. It does not diagnose a balance disorder. It doesn’t tell us why a particular child has poor coordination or dislikes physical activity. Those systems are much too complicated for that. What it may do is give us another reason to look at how effectively the patient is organizing the head and body against gravity.

What happens when the patient looks toward the floor? What happens when they look toward the ceiling? Can the head change position without obvious changes in the rest of the body? Does balance deteriorate? Does muscle tone appear to change? Does the patient compensate by moving the trunk? Do the feet move in an attempt to maintain stability? What happens when vision is removed and the patient has to rely more heavily upon vestibular and proprioceptive information?

These are essentially the kinds of responses examined in commonly used clinical assessments of retained TLR, and they raise a broader question:

How independent is the head from the rest of the body?

That independence matters for far more than standing still. Walking, running, reaching, throwing, catching, climbing stairs, bending over, and navigating uneven surfaces all require the nervous system to continually adjust the relationship between head position, posture, balance, and movement. Research examining Primitive Reflex activity in otherwise healthy preschool children has found relationships between greater retained-reflex activity, including TLR, and differences in motor performance. Other observational work has examined relationships between Primitive Reflex activity and gait. Those findings are interesting, but again they are merely associations. They do not establish that retained TLR caused the motor difficulty.

And Then There Is Vision

For those of us in Vision Therapy, this may be where TLR becomes particularly fascinating. Vision requires a stable platform. That doesn’t mean the body has to remain perfectly still: quite the opposite. Efficient visual function allows us to maintain useful visual information while the head and body are moving.

I can look at you while tilting my head. I can read a street sign while walking. I can watch a ball while running. I can look down at a page without my entire body collapsing into flexion. I can look up at a board without my body being pulled backward into extension. Those things seem remarkably simple until we consider how much neurological cooperation they require.

The eyes need to move within the head and the head needs to move relative to the body. The body needs to remain organized against gravity while vestibular information has to be reconciled with visual information. Proprioception provides information about body position while postural systems continually make adjustments so that the visual system has a useful platform from which to operate.

In other words:

The eyes need a stable body, but they also need a body that can move.

That distinction matters.

If changing head position continues to exert an unusually strong influence over posture or muscle tone, then visual activities involving changes in head position may require additional neurological effort. That does not mean retained TLR causes poor pursuits, saccades, convergence, accommodation, fixation, or visual perception. We don’t have evidence to make those claims. While there is emerging research examining relationships between persistent Primitive Reflexes, including TLR, and differences in fixation and ocular motility, that work is interesting, particularly for those of us working in developmental vision care, but it remains an emerging area of study and does not establish that the retained reflex caused the visual findings.

What it does give us is another reason to observe.

What Happens When the Eyes and Head Need to Separate?

Think about something as simple as looking down at a worksheet. Ideally, the eyes can move downward, the head can assume whatever position is comfortable, and the body can continue maintaining an efficient seated posture. But what if head flexion continues to produce an unusually strong flexor influence through the body? Now the visual task and the postural task may be competing with one another. Imagine looking upward toward a board, if extension of the head increases extensor influence through the body, maintaining comfortable posture while looking upward may require additional compensation. Again, this doesn’t mean TLR caused a reading problem or a binocular vision disorder, but it gives the Vision Therapist some interesting things to watch.

What happens to posture when the patient looks up or down? Can the eyes move vertically without excessive movement of the head? Can the head move without the trunk following? Does fixation change when head position changes? Does balance change when the patient follows a target upward or downward? Can the patient maintain visual attention while simultaneously controlling posture? What happens when we add movement? And perhaps most interestingly, what happens when we remove vision?

If performance deteriorates dramatically when the eyes are closed, that may tell us something about how much the patient has been relying on vision to help organize posture and balance, but it still doesn’t tell us that TLR caused the problem. However, it does tell us something important about how the systems may be working together.

Vision Isn’t Just Something We Do With Our Eyes

This is a theme that will probably appear repeatedly throughout this series, that vision develops inside a moving body. Before a child ever reads a letter on an eye chart, they have spent months learning about the world through movement. They lift their head. They turn toward things. They reach. They roll. They sit. They crawl. They pull themselves upright. Eventually they walk. Every one of those experiences provides information about space.

Where am I? Where is that object? How far away is it? What happens when I move toward it? What happens to what I see when my head moves? What does upright look like?

The vestibular system, proprioceptive system, postural system, and visual system are continuously exchanging information as those concepts develop, and TLR gives us an interesting window into the earliest stages of that relationship because it is fundamentally tied to head position and gravity. Eventually, the nervous system has to move beyond reflexively responding to gravity and begin using gravity as part of an increasingly sophisticated internal understanding of space, and vision becomes part of that process.

What Might This Look Like in the Vision Therapy Room?

This is where we may need to resist the temptation to create a checklist of “TLR symptoms.” It is very easy to find lists online claiming that retained TLR causes everything from poor posture and balance to reading problems, motion sickness, spatial difficulties, toe walking, weak muscle tone, poor coordination, and academic problems.

Some of those relationships may make developmental sense, some have limited observational evidence behind them, others are repeated much more confidently than the research justifies. Instead of asking whether the patient has a collection of symptoms that “proves” retained TLR, perhaps the more useful approach is to observe what happens when the systems associated with TLR are challenged.

Put the patient in a visual task and then change their head position, maybe even add movement. You might change the base of support, challenge balance, ask the eyes to move while the head remains still, ask the head to move while fixation remains stable, or even reduce visual information.

Then just watch.

Does posture change? Does visual performance change? Does balance deteriorate? Does the patient become slower? Do compensatory movements appear? Does something that looked automatic suddenly require considerable conscious effort?

Those observations may tell us much more than simply checking a box marked “Retained TLR.”

What About Attention and Behavior?

The Moro Reflex gave us a fairly natural path into emotional reactivity because Moro itself is a protective response to sudden change.

TLR is different, and we shouldn’t force the same conversation onto every Primitive Reflex. There isn’t sufficient evidence to say that a retained TLR causes a particular emotional or behavioral condition, but there is another whole-person question worth considering.

What does sustained physical effort do to attention?

Imagine sitting at a desk while your nervous system is continually spending resources maintaining posture, stabilizing the head, organizing the body against gravity, and providing a stable platform for the eyes. What would happen if you tried to read? Maintain fixation? Make accurate saccades? Keep your place? Shift attention? Remember what you read? Write an answer? Do it again?

If the physical foundation of the task requires more effort, eventually performance may deteriorate. The child may slump, they may put their head on the desk, they may constantly change position, they may avoid the task, attention may disappear, they may even tell us they are tired. That doesn’t mean retained TLR caused the behavior. It means that when we see behavior during a difficult visual task, it may be worth asking how much of the patient’s available neurological energy is already being spent simply organizing the body.

Sometimes what looks like an attention problem may be occurring in a patient who is working extraordinarily hard just to stay organized. That doesn’t give us a diagnosis. It really just gives us another question.

What Happens After Brain Injury?

Just as we discussed with Moro, traumatic brain injury creates another interesting, but scientifically complicated, part of this conversation. Concussion and other forms of TBI can disrupt balance, vestibular function, visual-vestibular interaction, eye movements, convergence, accommodation, sensory tolerance, and postural control. Patients may report dizziness when they move their heads, they may become disoriented in visually busy environments, walking while turning the head may become difficult, looking up or down may provoke symptoms, and closing the eyes while standing may suddenly make balance considerably more difficult. A patient who previously moved through the world without thinking about gravity may suddenly become very aware of it. Those are well-recognized consequences of disruption within visual, vestibular, and postural systems after brain injury. But once again, we need to separate that evidence from the Primitive Reflex question.

Can we say:

“The concussion caused the TLR to come back?”

The evidence does not allow us to say that confidently. As we discussed with Moro, neurological injury can disrupt higher-level control and inhibition, and primitive or release phenomena are recognized following neurological injury, but demonstrating disruption of vestibular and postural systems after concussion is not the same thing as demonstrating re-emergence of the developmental TLR.

Perhaps the more useful question is:

Has the injury changed the nervous system’s ability to regulate head position, posture, balance, and movement against gravity in a way that makes an underlying primitive pattern more apparent?

Again, we may not have the answer, but for the Vision Therapist working with brain injury, the question matters because visual rehabilitation doesn’t occur in isolation from vestibular and postural function. If looking down provokes symptoms, we need to notice. If moving the head disrupts fixation, we need to notice. If visual performance changes dramatically when balance is challenged, we need to notice. If the patient can perform a visual task sitting still but cannot maintain that performance while walking or moving the head, we need to notice. Not because every one of those findings means “retained TLR”, but because they tell us something about how the patient’s systems are, or aren’t, working together.

What Does the Research Actually Tell Us?

As with Moro, this is where we need to separate what we know from what we suspect. We know that the Tonic Labyrinthine Reflex is an early response involving the relationship between head position relative to gravity and changes in flexor and extensor tone. We know that as neurological development progresses, primitive responses become increasingly regulated while voluntary motor control and more sophisticated postural reactions emerge. Research in children has found associations between persistent Primitive Reflex activity, including TLR, and differences in motor performance, balance, sensory processing, and gait. There is emerging research examining relationships between Primitive Reflex activity, including TLR, and fixation and ocular-motor findings. There is, however, substantial evidence that traumatic brain injury can disrupt vestibular, postural, visual, and visual-vestibular function.

What we do not currently have sufficient evidence to say is:

• Retained TLR causes a particular binocular vision disorder
• Retained TLR causes poor reading
• Retained TLR causes an attention disorder
• Retained TLR causes a particular emotional condition
• Integrating TLR will treat those conditions
• A concussion routinely causes the developmental TLR to return

Those are stronger claims than the evidence supports, and once again, acknowledging that doesn’t make TLR less interesting. On the contrary, it makes the clinical conversation considerably more useful.

What Should the Vision Therapist Take Away?

Perhaps the value of identifying a retained TLR isn’t simply being able to say that the reflex is present. Perhaps its value is that it reminds us to look more carefully at the relationship between the head, the body, gravity, and vision. What happens when the head flexes? What happens when it extends? Can the eyes move independently of the head? Can the head move independently of the trunk? Can the patient maintain fixation while the head moves? Can they maintain posture while the eyes move? What happens when balance becomes more challenging? What happens when visual information is reduced? And what happens when we ask all of those systems to work at the same time? Because ultimately, the goal isn’t simply to inhibit a reflex; rather, the goal is to help the nervous system develop increasingly efficient options.

A child should eventually be able to look down without the entire body needing to flex, or look up without being pulled into extension. We hope they can move the head without losing balance, move the eyes without moving the whole body, maintain posture without consciously thinking about it, and use vision while the body moves through a world in which gravity never stops acting upon it. That is a much bigger conversation than whether a TLR test is positive or negative. A retained TLR is not a diagnosis, nor is it an explanation for everything we’re seeing. It is another clinical observation that may help us ask better questions about how efficiently the patient’s visual, vestibular, proprioceptive, motor, and postural systems are working together.

And perhaps TLR reminds us of something incredibly basic that is easy to forget: before the eyes can efficiently tell us where everything else is, the nervous system first has to develop a reliable sense of where we are.

Dr. Skeffington, table for one?

Stay tuned for Part Four. Up next: the Asymmetrical Tonic Neck Reflex (ATNR) and the developing relationship between the eyes, the hands, and the two sides of the body.

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References

Gieysztor EZ, Sadowska L, Choińska AM, Paprocka-Borowicz M. Persistence of primitive reflexes and associated motor problems in healthy preschool children. Archives of Medical Science. 2018;14(1):167–173.

Pecuch A, Gieysztor E, Wolańska E, Telenga M, Paprocka-Borowicz M. Primitive Reflex Activity in Relation to Motor Skills in Healthy Preschool Children. Brain Sciences. 2021;11(8):967.

Gieysztor EZ, Choinska AM, Paprocka-Borowicz M. Primitive Reflex Activity in Relation to the Sensory Profile in Healthy Preschool Children. International Journal of Environmental Research and Public Health. 2020;17(21):8210.

Gieysztor EZ, Kowal M, Paprocka-Borowicz M. Primitive Reflex Factors Influence Walking Gait in Young Children: An Observational Study. International Journal of Environmental Research and Public Health. 2022;19(7):4070.

Domingo-Sanz VA. Persistence of Primitive Reflexes Associated with Asymmetries in Fixation and Ocular Motility Values. Journal of Eye Movement Research. 2024;17(2):1–33. doi:10.16910/jemr.17.2.5.

Master CL, Bacal D, Grady MF, et al. Vision and Concussion: Symptoms, Signs, Evaluation, and Treatment. Pediatrics. 2022;150(2):e2021056047.

Master CL, Bacal D, Grady MF, et al. Evaluation of the Visual System by the Primary Care Provider Following Concussion. Pediatrics. 2022;150(2):e2021056048.

Wallace B, Lifshitz J. Traumatic brain injury and vestibulo-ocular function: current challenges and future prospects. Eye and Brain. 2016;8:153–164.