VT Works

Up to this point in this series, we’ve been asking what happens when an early developmental response remains more influential than it should. Moro introduced us to sudden change and protective reactivity. TLR brought us into a relationship with gravity. ATNR explored the developing relationship between the eyes, the hands, and the two sides of the body. STNR brought us to the upper and lower body, posture, and near vision. And most recently, Spinal Galant gave us an opportunity to think about sensory information, the trunk, and the nervous system’s developing ability to decide when something requires a response.

Head Righting is different, and that difference is very important.

Head Righting isn’t another Primitive Reflex that we’re waiting for the nervous system to inhibit, since righting reactions represent a more advanced level of postural development. Rather than asking why an early response remains present, this time we’re going to look at something the developing nervous system learns to do increasingly well: find balance. Perhaps the simplest question is also the most interesting:

How does the nervous system know which way is up?

What Is Head Righting?

Tilt your body to the side while you’re sitting in your chair.

What happens to your head?

Unless you’re deliberately allowing it to fall with your body, your head will probably try to remain relatively upright.

Now, imagine an infant whose nervous system is still figuring all of this out. Early in development, the relationship among the head, body, and gravity is still evolving. As postural control develops, righting reactions increasingly help orient the head appropriately in space when the position of the body changes, representing a developmental transition.

The body tilts, the head doesn’t necessarily have to follow, since the nervous system has another option. Research on infant motor development describes a general progression from the predominance of earlier Primitive Reflex patterns toward increasingly mature postural reactions, including righting, equilibrium, and protective responses. That distinction is important enough to say again:

Head Righting is not a Primitive Reflex in the same sense as Moro, TLR, ATNR, STNR, or Spinal Galant.

It belongs to the developing family of postural/righting reactions that help us orient ourselves relative to gravity and the environment.

But Which Way Is Up?

This is where things get interesting, because there isn’t only one source of information telling us where upright is. The vestibular system contributes information about the position and movement of the head relative to gravity, while somatosensory and proprioceptive information tells us about the relationship between different parts of the body and the surface supporting us. Then there is vision, which gives us an enormous amount of information about the environment and our orientation within it.

Walls are usually vertical, floors are usually horizontal, and the horizon provides a powerful reference for upright. Objects around us provide spatial relationships that help us understand where we are, and somehow, the nervous system has to put all of that information together. Which means the question may not simply be: “Which way is up?”

Perhaps the important question is:

Which source of information should I trust right now?

Labyrinthine and Optical Righting

Two terms commonly encountered when discussing Head Righting are labyrinthine righting and optical righting. Labyrinthine Head Righting relies heavily on vestibular information. Even without visual information, movement away from vertical can produce an attempt to return the head toward an upright orientation, while Optical Righting adds visual information to the problem. Open the eyes and suddenly the nervous system has another powerful source of information about orientation in space. The two aren’t competing systems where one simply turns on and the other turns off. Normal postural orientation involves information from multiple sensory systems being used together.

Close your eyes and you can still tell that you’re leaning. Open your eyes and now you have more information. Touch a stable surface and you have more information again. The nervous system is constantly combining these signals, and depending upon the situation, it may rely more heavily on one source than another.

The Head Carries the Eyes

Why does keeping the head appropriately oriented matter so much? Well, among other things, the head carries the eyes, and the position of the head changes the visual problem. Tilt the head and the eyes are now operating from a different orientation. Move the head and the visual scene moves relative to the retina, or even better, walk through the environment and the head is constantly accelerating, decelerating, rotating, and changing position. Yet somehow, most of the time, the world doesn’t appear to bounce around every time we take a step. That isn’t Head Righting alone.

The vestibulo-ocular reflex, ocular-motor systems, proprioception, postural control, prediction, and other neurological processes all contribute to visual stability during movement, but Head Righting gives us another piece of the developmental puzzle. Before the eyes can efficiently guide us through space, the nervous system also needs a reliable way of understanding where the head is within that space.

Vision Is Part of the Conversation

For Vision Therapists, this may be where Head Righting becomes especially interesting. Vision isn’t simply receiving information from a body that has already figured out where it is: vision participates in figuring out where we are. We use visual information to orient ourselves, we use the environment as a reference, we use visual motion to help determine whether we are moving or something around us is moving, and we use visual information along with vestibular and somatosensory information to maintain posture and balance.

In other words, vision doesn’t sit on top of the postural system, it’s simply part of the conversation, and sometimes the different systems don’t completely agree.

What Happens When Vision and Gravity Disagree?

Imagine sitting in a stationary train when the train beside you begins to move. For a brief moment, you may feel as though your train is moving. Nothing happened to your vestibular system. Your body didn’t move. However, the visual information was powerful enough to temporarily change your perception of movement. Or even better, think about standing in a room while the visual environment around you moves.

Your vestibular system may say: “We’re standing still.”

Your feet may say: “We’re standing still.”

Your eyes may be suggesting something different and the nervous system has to sort that out. This ability to adjust how much importance is given to different sensory information is often discussed in terms of sensory weighting or sensory reweighting.

The goal isn’t to always trust vision alone, it isn’t to always trust the vestibular system alone, and it isn’t to always trust proprioception alone. The goal is flexibility, by using the information that is most reliable for the situation. Once again, the nervous system needs choices.

What Might This Look Like in the Vision Therapy Room?

As we’ve done throughout this series, perhaps the most useful thing we can do is change one variable and observe.

Have the patient stand comfortably and observe what happens to the head. Tilt the body and observe whether the head remains relatively upright. Change the visual environment and compare responses. Close the eyes and repeat. Observe changes. Ask the patient to maintain fixation while the body changes position. What happens? Add head movement. Add balance. Change the support surface. Add a visually demanding task. What changes when vision is reliable? What changes when visual information is reduced? What changes when visual information becomes more complicated? Does the patient stiffen? Does the head tilt with the body? Does balance deteriorate? Does fixation become more difficult? Does the patient become uncomfortable? Do they become unusually dependent upon vision? Does performance improve dramatically when another source of sensory information is added? None of those observations gives us a diagnosis by itself, but they may tell us something about how the patient is using vision, vestibular information, proprioception, and posture together.

That’s useful information.

What About the Visual System Itself?

Here again, we need to resist turning Head Righting into an explanation for every visual problem. A poorly developed or inefficient Head Righting response does not automatically mean a patient will have convergence insufficiency, accommodative dysfunction, poor pursuits, poor saccades, or another specific binocular or ocular-motor disorder. That’s too large a leap. But head position certainly changes the circumstances under which the visual system has to operate. The eyes don’t function independently of the head. The head doesn’t function independently of the body. The body doesn’t function independently of gravity.

So rather than saying: “Head Righting caused the visual problem.”

Perhaps we ask: “What happens to visual performance when the patient’s relationship with gravity, posture, or head position changes?”

That’s something we can observe.

The Eyes Open and the Eyes Closed

There is another wonderfully simple clinical idea buried inside Head Righting. Take vision away and watch what changes?

We use our eyes for far more than identifying letters on an eye chart. Vision contributes to balance, orientation, movement, navigation, and our perception of where we are relative to the world around us. Close the eyes and the nervous system has to rely more heavily on other information. Open them and vision returns to the conversation. That doesn’t mean better performance with the eyes open proves a visual problem, since most people use vision to help maintain balance, but the degree of change may be interesting, and so might the quality of the response.

Does the person immediately become unstable? Do they stiffen? Does the head position change? Do they become anxious about moving? Can they maintain orientation while another sensory system becomes less available?

Again, we’re observing the system rather than trying to force every observation into a diagnosis.

What Happens After Brain Injury?

This is one area where the conversation becomes particularly relevant. As most are aware, concussion and other forms of traumatic brain injury can affect visual function, vestibular function, balance, postural control, gaze stabilization, motion sensitivity, and the ability to efficiently combine information from multiple sensory systems.

A patient may tell us:

“I feel fine sitting still, but everything changes when I move.”

Or:

“I can read, but walking through the grocery store makes me dizzy.”

Or:

“I feel like the room moves when I turn my head.”

Or simply:

“I don’t feel steady anymore.”

Those complaints aren’t evidence of an abnormal Head Righting reaction by themselves, but they remind us how closely vision, vestibular processing, head movement, and postural control are connected. Research following concussion has demonstrated altered responses to visual and vestibular information during postural tasks, reinforcing the idea that balance after brain injury may involve more than one sensory system.

So rather than asking: “Did the concussion damage Head Righting?”

Perhaps the more useful question is: “Has the injury changed how effectively the patient combines visual, vestibular, and somatosensory information to understand where they are in space?”

That question gives us considerably more room to observe what’s actually happening.

What Does the Research Actually Tell Us?

Compared with some of the retained Primitive Reflex claims we’ve discussed throughout this series, the basic science behind righting reactions and multisensory postural control is much stronger. We know that righting reactions emerge as part of normal postural development. We know infant development generally progresses from greater influence of early Primitive Reflex patterns toward increasingly sophisticated righting, equilibrium, and protective reactions. We know visual information contributes to postural orientation and balance. We know vestibular information contributes to the perception of head position and movement relative to gravity. We know somatosensory information contributes information about the body and its relationship to the supporting surface. And we know the nervous system normally combines information from these systems rather than depending exclusively on one of them. We also have substantial evidence that concussion can disturb visual, vestibular, and postural function.

What we should not conclude from that is that every balance problem, head tilt, visual problem, or post-concussion symptom represents a poorly developed Head Righting reaction. Nor should we assume that “integrating Head Righting” will treat a specific visual, vestibular, learning, or neurological disorder.

Once again, observation and explanation are not the same thing.

What Should the Vision Therapist Take Away?

Head Righting is different from everything else we’ve discussed so far. We’re no longer talking primarily about an early response that needs to become less influential; rather, we’re talking about the development of a better option. The body moves, the head can respond. Vision contributes information, the vestibular system contributes information, the body contributes information, and somehow the nervous system learns to put all of it together. Perhaps development isn’t simply a story about reflexes disappearing, it’s also a story about choices appearing.

Early in life, one stimulus may produce a relatively predictable response. As the nervous system develops, vision, vestibular information, proprioception, touch, posture, and movement increasingly work together, giving us more ways to respond to the world around us. Head Righting gives us a wonderful example. Tilt the body, the head doesn’t simply have to follow.

The nervous system has another option.

And maybe that’s what we’ve really been talking about throughout this entire series, not simply eliminating reflexes, but developing choices.

Stay tuned for Part Eight, where we’ll bring the pieces together and take one final look at Primitive Reflexes, vision, development, and the whole person.

---

References

1. Mandich M, Simons CJ, Ritchie S, Schmidt D, Mullett M. Motor development, infantile reactions and postural responses of preterm, at-risk infants. Developmental Medicine & Child Neurology. 1994;36(5):397–405. doi:10.1111/j.1469-8749.1994.tb11865.x. PMID: 8168658.
2. Haley SM. Sequential analyses of postural reactions in nonhandicapped infants. Physical Therapy. 1986;66(4):531–536. doi:10.1093/ptj/66.4.531. PMID: 3960980.
3. Maekawa K. The Examination of Equilibrium Reaction in Infancy and Early Childhood. Jibi Inkoka. 1972;18(2):132–140. doi:10.11334/jibi1954.18.2_132.
4. Master CL, Bacal D, Grady MF, Hertle R, Shah AS, Strominger M, Whitecross S, Bradford GE, Lum F, Donahue SP. Vision and Concussion: Symptoms, Signs, Evaluation, and Treatment. Pediatrics. 2022;150(2):e2021056047. doi:10.1542/peds.2021-056047. PMID: 35843991.
5. Wallace B, Lifshitz J. Traumatic brain injury and vestibulo-ocular function: current challenges and future prospects. Eye and Brain. 2016;8:153–164. doi:10.2147/EB.S82670. PMID: 28539811.
6. Nowak MK. Visual and vestibular involvement in postural deficits following concussion. Journal of Neurophysiology. 2018;120(2):391–393. doi:10.1152/jn.00895.2017. PMID: 29897861.
7. Caccese JB, Santos FV, Yamaguchi F, Jeka JJ. Persistent visual and vestibular impairments for postural control following concussion. Neurology. 2020;95(20 Suppl 1):S14–S15.