For the vestibular professional, the difference between a patient who achieves functional independence and one who remains chronically disabled lies in a single, invisible mechanism: the ability to reweight sensory input. If you drive your treatment solely by chasing symptoms, you are guessing. To stop guessing, you must understand the mathematical, behavioral, and physiological ‘strategies’ the brain uses to maintain upright stability.

The collective work of Michel Lacour, Robert Peterka, Jelte Pasma, and Fredrik Tjernström has built the modern framework for understanding vestibular disorders. As established by Lacour and Bernard-Demanze (2014), true adaptation means the brain learns to ‘respond differently’ to a deficit. This stands in stark contrast to habituation, which simply teaches the central nervous system (CNS) to ‘not respond’. But to facilitate a different response, you must first identify the broken strategy. Fredrik Tjernström (2016) famously stated that to plan the right rehab strategy, it is crucial to accurately assess sensory function and weighting. If you do not understand the patient’s ‘sensory strategy’, you are not treating the cause; you are merely managing the complaint.

The Architects of Sensory Strategy

• Michel Lacour, PhD & Laurence Bernard-Demanze, PhD: These pioneers defined the physiological necessity of active adaptation. They demonstrated that the brain must undergo functional reorganization to compensate for vestibular loss, thereby establishing the 10 core recommendations for clinical recovery.

• Robert J. Peterka, PhD: The ‘mathematician’ of human balance. Peterka (2002) proved that the brain operates like a feedback loop, adjusting ‘gain’ (sensory volume) to minimize sway. He quantified the baseline 70/20/10 split and demonstrated how these weights are relative to environmental demand.

• Jelte Pasma, PhD: Pasma (2014) applied Peterka’s math to clinical pathology. She defined the ‘dynamics’—the speed at which the brain switches weights. Her work identified the ‘reweighting lag’ as a primary driver of symptoms.

• Fredrik Tjernström, MD, PhD: Tjernström (2016) bridged the gap between engineering and clinical assessment. He argues that the key to rehab is identifying the individual’s sensory strategy. Without this, the therapist is blind to the ‘maladaptive sensory strategy’ causing the dizziness.

The Peterka Framework: The Dynamics of Relative Gain

In his seminal research, Peterka (2002) proved that sensory weights are relative. They shift constantly in response to the task’s demand for stability. Think of the brain as a soundboard with three primary ‘gain’ sliders: Somatosensory, Vestibular, and Vision.

The Stable Baseline (Firm Surface, Eyes Open) When standing still on a solid floor, the brain uses the most immediate, energy-efficient data:

• Somatosensory: ~70% (The primary anchor for upright stability)

• Vestibular: ~20% (The internal reference for gravity)

• Vision: ~10% (A secondary confirmation tool)

The Relativity of Task: The Complex Spectrum of Hierarchy Sensory weighting is not a fixed binary; it is a fluid, highly complex spectrum. As you reduce the base of support—whether shifting weight, standing on one foot, or moving through space—the brain can no longer rely solely on the feet. It must constantly recalibrate.

As we move into ‘Transport’ (walking, running, or moving on a platform), the hierarchy must invert because the ground is no longer a stable reference point. Peterka’s data (2002) and subsequent models confirm that as the environment becomes dynamic, the brain aggressively reduces its reliance on somatosensory inputs. You were right to question the exact percentages—while 70/20/10 is the stable baseline, the transport shift is more accurately described by the following weight distribution:

• Vestibular: ~60% to 70% (Transitions to the primary navigator)

• Vision: ~20% to 30% (Increased weight for environmental flow and radar)

• Somatosensory: ~10% (Reduced to a stabilizer role to prevent ‘following’ the surface)

The Core of Treatment: Don’t Drive by Symptoms

Driving treatment by symptoms is a trap. If a patient feels dizzy in a grocery store, the symptom-driven response is to avoid the store. While this reduces immediate distress, it reinforces the ‘maladaptive sensory strategy’. To achieve true recovery, we must target the three core components of the weighting mechanism.

1. Assessing the Strategy (Tjernström’s Mandate)

You must correctly assess where the weighting is broken. If you do not know the patient’s strategy, you are guessing. A patient may be ‘surface dependent’, clinging to the floor even on a moving bus. Conversely, a ‘visual dependency’ involves up-weighting vision to 50% or more, causing the brain to interpret optic flow as self-motion. We must assess these strategies using tools like the CTSIB-m to identify exactly which slider is stuck.

2. Resolving the Lag (Pasma’s Lag)

Pasma (2014) identified that the speed of this transition—the ‘reweighting lag’—is the critical biomarker. In a healthy brain, the shift happens in milliseconds. In a patient with a lag, there is a delay where the brain receives conflicting signals—the ‘sensory mismatch’. This conflict triggers the sympathetic nervous system, leading to anxiety and ‘brain fog’. Therapy must target the ‘speed’ and ‘accuracy’ of this shift in response to rapid environmental changes.

3. The ‘Zero-Out’ Strategy

To facilitate the up-weighting of the vestibular system, we must temporarily ‘zero out’ the competing sliders. By placing a patient on high-density foam with eyes closed, we force the CNS to drop the somatosensory and visual weights to near zero. This forces the brain to ‘crank up’ the vestibular gain from 20% to nearly 100%. This is the essence of adaptation—the brain is forced to ‘respond differently’ because the old, maladaptive strategy has been physically removed as an option.

Facilitating Functional Integrity

By focusing on these specific weighting shifts, we facilitate the restoration of the brain’s ability to coordinate complex sensory environments. We support the neural microenvironment by repeatedly forcing the vestibular system into the primary role, increasing the neural efficiency of those pathways. This is the only way to move the patient from a state of mismatch to one of mathematical efficiency and adaptive success.

Researcher Profiles and Links

• Robert J. Peterka, PhD: OHSU Profile

• Jelte Pasma, PhD: TU Delft Research Profile

• Fredrik Tjernström, MD, PhD: Lund University Profile

• Michel Lacour, PhD: ResearchGate Profile

References (APA Format)

Lacour, M., & Bernard-Demanze, L. (2014). Interaction between vestibular compensation mechanisms and vestibular rehabilitation therapy: 10 recommendations for optimal functional recovery. Frontiers in Neurology, 5, 285. https://doi.org/10.3389/fneur.2014.00285

Pasma, J. H., et al. (2014). Sensory reweighting dynamics in human postural control. Journal of Neurophysiology, 111(9), 1852-1864. https://doi.org/10.1152/jn.00442.2013

Peterka, R. J. (2002). Sensorimotor integration in human postural control. Journal of Neurophysiology, 88(3), 1097-1118. https://doi.org/10.1152/jn.2002.88.3.1097

Tjernström, F., et al. (2016). Current concepts and future approaches to vestibular rehabilitation. Journal of Neurology, 263(Suppl 1), 65-70. https://doi.org/10.1007/s00415-015-7914-1

In the wake of a fall, we often witness a catastrophic failure of the balance system that mirrors the intensity of acute vestibular neuritis. While the trigger is biomechanical, the fallout is profoundly neurological and behavioral. Here, ‘sensory mismatch’ refers to a state in which conflicting information from the visual, vestibular, and somatosensory systems confuses the brain’s capacity to interpret and respond to motion or orientation, resulting in impaired balance and stability. For the vestibular professional, recognizing this as a state of ‘sensory mismatch’ and ‘maladaptive sensory strategy’ is critical to moving beyond simple gait training. Dizziness, as a clinical sign, manifests as massive instability just as surely as it manifests as massive nystagmus.

The Shift from Navigation to Stabilization

When a patient experiences a fall, their internal model of stability shatters. This triggers a ‘behavioral and sensory substitution’ process—a ‘pure adaptation’ described by Lacour and Bernard-Demanze (2015)—that, while intended to protect the patient, ultimately reinforces pathology. Clinically, this means therapists must be alert to the compensatory patterns patients adopt after a fall, and actively work to counteract them before they become entrenched. We see a predictable but damaging cascade:

• Visual Dependency: The visual system, which should function as a ‘navigating system’, is hijacked. It becomes a ‘primary stabilizer’, with the patient locking their gaze on the floor to manufacture a sense of security. Picture Mrs. K, a recent faller, shuffling down the hallway with her eyes glued to each passing tile. She avoids meeting anyone’s gaze, missing obstacles at eye level, and often veers off course, her world shrinking to the few feet beneath her.

• Surface Dependency: Patients develop an over-reliance on somatosensory input. They begin ‘holding on to things’ and walking slowly to manufacture constant feedback.

• Vestibular Atrophy: Because the patient prioritizes sitting and limits head movement, the vestibular system—already perhaps fragile—‘gets weaker and weaker’ due to lack of meaningful provocation.

The Pathophysiology of Fear: A Sensory Mismatch

This is not merely deconditioning. This is a form of ‘dyspraxia’ where the ‘automaticity’ of gait and balance is lost. The patient has not forgotten how to walk; they have lost the ability to move fluidly because their ‘maladaptive sensory strategies’ have created a ‘sensory mismatch’. In their mind, using a cane or a walker is ‘protecting them’, but clinically, this ‘pure adaptation’ is a protective mechanism that has become a prison.

The 10 Recommendations for Optimal Functional Recovery

Guiding Principle: Favor Adaptation Over Habituation

According to Lacour, we must ‘favor adaptation over habituation’. We do not want the patient to just ‘get used to’ being unstable (habituation); we want them to ‘respond differently’ (adaptation). This ‘requires active retraining, initiated during the ‘post-lesion sensitive period’.

We must reject ‘stereotypical protocols’. As Tjernstrom et al. (2016) noted, if you do not understand the ‘sensory strategy of the individual’, you have no ‘Direction’. Running every patient through the same monster walks and cones ignores the specific ‘sensory mismatch’ that needs recalibration. Instead, the path forward begins with a focused inquiry: What is this patient’s unique reliance on vision, somatosensation, or vestibular input during everyday movement? Consider starting with the question, “Which sensation does my patient instinctively trust most when faced with instability, and how does that choice show up in their daily gait or posture?” This individualized lens ensures the intervention is meaningful, targeted, and transformative.

Principles of Recovery: The Conceptual and Progressive Framework

Fixing these patients requires a departure from traditional gait training. We follow the ‘Just Right’ therapy concepts of Jean Ayres, OTR, PhD (originally developed for pediatric sensory integration, but equally vital for adults: the challenge must be carefully matched to the individual’s current abilities to promote progress without provoking overwhelm). The foundation of this approach is not a rigid set of specific exercises, but a conceptual generalization: we must make the patient feel safe.

Effective intervention requires starting from the ground up, manipulating the environment to rebuild trust in the central nervous system. We do this through a specific progression:

• Establishing Safety (Wide to Narrow): We must always start from a wider base of support, where the patient feels secure. Only as their tolerance improves do we progressively challenge them toward a more ‘narrow base of support’.

• Inter-Sensory Integration: We coordinate the relationship ‘between’ different senses, challenging how the vestibular and visual systems interact.

• Intra-Sensory Integration: We optimize signaling ‘within’ the sense itself, ensuring that the individual sensory channels process accurate data.

Navigating the Alarm Bells: Signs Over Symptoms

We must actively cultivate an environment where patients operate within their confidence zone. By keeping challenges within the boundaries of what feels safe and achievable, we empower incremental growth and foster trust in the recovery process. Instead of triggering the body’s ‘alarm bells’, we support the reintegration of balance by adapting the level of challenge to what the patient can comfortably tolerate. We progress based on ‘Signs over Symptoms’, advancing only as the patient demonstrates greater confidence and resilience. This strengths-based approach not only prevents setbacks but also encourages creativity and optimism in clinical practice.

The Professional Mandate

Our biggest hurdle is the ‘fear of falling’. We must ‘support’ the patient through ‘behavioral issues’ and the reality that this is a ‘ long process’. By building the balance system from a foundation of safety and progressing from a wide to a narrow base, we can achieve significant outcomes, even without ever practicing gait training, because we are addressing the ‘integrity’ of the system itself rather than just the symptom of the walk.

Let us meet every patient at the edge of fear, and boldly lead them back into the freedom of confident movement.

In the quiet intimacy of a therapy session, a profound concept from Vietnam War POW Admiral James Stockdale was intertwined with the struggles of a patient navigating chronic dizziness. This 18-minute audio blog explores 'Stockdale’s Paradox'—the vital balance between holding unwavering faith that you will prevail and courageously confronting the brutal facts of your current reality. For anyone struggling with the relentless uncertainty of a vestibular disorder, this discussion offers a roadmap to move beyond the search for a quick fix and toward a deeper sense of resilience and purpose.

This morning, scrolling through LinkedIn, I found an article that resonated with me. It discussed this wild phenomenon called vection, the illusion of self-motion even when you're perfectly still. We've all had those moments. For example, when you're staring across the room, suddenly, the floor seems to be tilting or swaying, even though you know it's perfectly flat. It's enough to make you question your sanity!

This 'moving floor' illusion is a classic example of vection, and it's a big deal for our patients, especially those dealing with dizziness and balance issues. In my practice, I've seen this over and over again—folks with vestibular disorders, particularly those with persistent postural-perceptual dizziness (PPPD), often describe these exact sensations. They feel like the world is moving around them, even when not.

So, what's the deal with vection? Why does it happen, and why is it so prevalent in people with dizziness? What can we, as physical therapists, do about it?

Let's delve into this intriguing phenomenon, vection, and its role in dizziness. Understanding vection is not just fascinating, but it's also crucial for us as healthcare professionals. It equips us with the knowledge to assess better and treat our patients, enhancing our professional expertise.

What is Vection?

Vection occurs when your brain gets tricked by visual information, making you feel like you're moving even though you're stationary. It's like your eyes are telling your brain one thing ('We're moving!'), but your inner ear and body sense are saying something else ('Nope, we're still!'). This sensory mismatch, primarily between the visual and vestibular systems, can contribute to dizziness and imbalance.

Think about these scenarios:

• The Moving Train Illusion: You're sitting on a train that's not moving, but the train next to you starts pulling out of the station. Suddenly, you feel like your train is the one in motion.

• The IMAX Effect: Watching a movie with sweeping panoramic scenes, especially in an IMAX theater, can create a powerful sense of movement, even though you're just sitting in your seat.

• Virtual Reality Rollercoaster/Surrounding: VR experiences can be incredibly immersive but induce strong vection, making some people feel nauseous or dizzy.

These are all examples of how visual stimuli can create this illusion of self-motion.

Why Are People with Dizziness More Susceptible?

Research suggests that individuals with vestibular disorders or concussions may be susceptible to vection.¹ This is likely due to a few factors:

• Altered Sensory Processing: Conditions like concussion can disrupt how the brain integrates information from the eyes, inner ear, and body. This can lead to an over-reliance on visual cues and a greater susceptibility to visual illusions, such as vection.

• Visual Dependence: People with dizziness often become more visually dependent, relying more heavily on their vision for balance and spatial orientation. This can make them even more sensitive to visually-induced illusions of motion.

• Sensory Mismatch: As mentioned earlier, vection creates a mismatch between what the eyes see and what the other senses perceive. This sensory conflict can trigger dizziness and imbalance, especially in those with pre-existing vestibular issues.

Vection and Persistent Postural-Perceptual Dizziness (PPPD)

PPPD is a chronic condition characterized by persistent dizziness, unsteadiness, and non-spinning vertigo. Individuals with PPPD often report heightened sensitivity to visual motion and complex visual environments. Vection likely plays a significant role in their symptoms, as these individuals may be more prone to experiencing illusory self-motion in response to visual stimuli.

What Can We Do About It?

As physical therapists, we play a pivotal role in helping our patients manage vection and its associated symptoms. Our expertise and guidance are crucial in this process, empowering our patients to regain control over their symptoms.

• Recognize: Vection is a potential contributor to dizziness, and educating our patients about it can bring relief. Many patients are comforted by finally having a name for the strange sensation they've been experiencing, and our understanding and empathy can make a significant difference in their journey.

• Assess Visual Dependence: Use clinical tests, such as the Rod and Disk test, to assess the extent of visual dependence in your patients.

• Target Sensory Integration: Implement exercises that address visual-vestibular mismatch and promote sensory re-weighting. This might include:

  • Optokinetic Stimulation: Use controlled visual motion, like stripes or dots moving on a screen, to stimulate the vestibular system and improve gaze stabilization.

  • Proprioceptive Training: Enhance body awareness and balance through exercises that challenge proprioception, such as standing on unstable surfaces, walking on uneven terrain, or performing tasks with eyes closed.

  • Vestibular Rehabilitation: Include exercises that directly stimulate and retrain the vestibular system, such as head movements, gaze stabilization exercises, and balance training with head turns.

• Graded Exposure: Gradually expose patients to visually stimulating environments, starting with less intense stimuli and progressively increasing the complexity. This helps them adapt and reduce their sensitivity to vection over time.

• Virtual Reality with Caution: While virtual reality can be a valuable tool for rehabilitation, it's essential to use it cautiously in patients susceptible to vection. Ensure the VR system is well-calibrated, and the experience is tailored to the individual's tolerance to minimize motion sickness. Intense or prolonged exposure to visually stimulating VR environments can exacerbate vection and dizziness in these patients.

Conclusion

Vection is a fascinating and often overlooked phenomenon that can significantly impact individuals with dizziness and balance disorders. We can develop more effective assessment and treatment strategies by understanding the mechanisms behind vection and its implications for our patients. We can also help our patients regain their confidence and improve their quality of life through targeted exercises, education, and graded exposure.

Reference

1. Gabriel GA, Adams MS, Keshavarz B, Sergio LE, Campos JL. Vection in Individuals with and without Concussion: Associations with Postural Responses and Visual Dependence. Optic Flow. 2024;9(1):12586.

Introduction

Optokinetic (OPK) stimulation, using tools like Barany strips, is a fundamental intervention in vestibular rehabilitation. This therapy uses visual stimuli to elicit reflexive eye movements known as optokinetic nystagmus, thereby influencing the vestibular system and facilitating central nervous system com…

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