AUTHOR: 
AERYN O'HALLORAN

Mind–body practitioner and educator specializing in nervous system regulation and chronic illness.

DATE: 
DECEMBER 18, 2025

Sensory Modulation:

an overlooked nervous system function in POTS/dysautonomia and Lyme Disease

Sensory Modulation: 

an overlooked nervous system function in POTS/dysautonomia and Lyme Disease

This article explains how the nervous system regulates sensory input automatically, often outside conscious awareness. You do not need to understand every sentence for this to be useful. Many people recognize their experience in this material before they can fully explain it.



A NOTE FOR READERS

Sensory modulation refers to the nervous system’s capacity to regulate the intensity and impact of sensory input in order to maintain physiological stability and function. When this regulatory capacity is reduced, ordinary levels of stimulation may trigger exaggerated autonomic responses, contributing to symptom patterns commonly observed in chronic illness, POTS/dysautonomia, autoimmune conditions, and post-viral syndromes. Drawing on occupational therapy research and neurophysiological models, this article examines sensory modulation as an under-recognized regulatory function of the nervous system and explores its relevance to multisystem symptom persistence in the absence of ongoing infection or structural pathology.



ABSTRACT

Sensory modulation refers to the nervous system’s capacity to regulate the intensity, timing, and prioritization of sensory input in order to maintain physiological stability and function.

This includes sensory signals originating both externally (light, sound, movement, touch) and internally (heart rate, breath, pain, temperature, visceral sensation).

Rather than passively receiving sensation, the central nervous system continuously evaluates and adjusts how strongly these signals are registered, as well as how much and what kind of response they elicit. This regulatory process is essential for autonomic balance, cognitive availability, task performance, and recovery following stress or exertion.

When sensory modulation is working effectively, sensory input can be processed without triggering excessive physiological activation or withdrawal. When it is strained, ordinary levels of stimulation may provoke disproportionate autonomic responses.







Introduction

From a neurophysiological perspective, sensory modulation is closely tied to arousal regulation. It reflects how efficiently the nervous system can move between states of activation and rest, and how accurately it can scale responses to the actual demands of a situation.











This flexibility supports physiological stability across changing conditions. 

When sensory modulation capacity is reduced, the system becomes less precise. Input that would normally be tolerated may trigger defensive autonomic responses, while recovery from stimulation becomes slower and less reliable.







From a neurophysiological perspective, sensory modulation is closely tied to arousal regulation. It reflects how efficiently the nervous system can move between states of activation and rest, and how accurately it can scale responses to the actual demands of a situation.

A nervous system with adequate regulatory capacity can:

⋆ increase arousal when action or attention is required
⋆ decrease arousal once the demand has passed
⋆ return to baseline without prolonged residual activation

This flexibility supports stability across changing conditions. 

When sensory modulation capacity is reduced, the system becomes less precise. Input that would normally be tolerated may trigger defensive autonomic responses, while recovery from stimulation becomes slower and less reliable.






A nervous system with adequate regulatory capacity can:

⋆ increase arousal when action or attention is required
⋆ decrease arousal once the demand has passed
⋆ return to baseline without prolonged residual activation







Sensory Modulation as a Regulatory Process

Impaired sensory modulation does not present as a single symptom. It presents as instability across systems, often fluctuating day to day or moment to moment.

Common patterns include:











From an autonomic standpoint, this reflects reduced flexibility between sympathetic activation and parasympathetic recovery.

Rather than transitioning smoothly between alertness and rest (activation and recovery), the nervous system may remain biased toward sustained sympathetic dominance (e.g., tachycardia, hypervigilance, insomnia) or toward compensatory hypoarousal (e.g., exhaustion, shutdown, dissociation).

These are not transient emotional states. They are state-dependent physiological patterns that shape symptom expression across multiple systems.







Impaired sensory modulation does not present as a single symptom. It presents as instability across systems, often fluctuating day to day or moment to moment.

Common patterns include:

⋆ exaggerated cardiovascular responses to positional change or mild exertion
⋆ heightened sensitivity to light, sound, temperature, or internal bodily sensations
⋆ rapid onset of fatigue, dizziness, or cognitive “fog” following minimal stimulation
⋆ difficulty returning to baseline after stress, activity, illness, or emotional load

From an autonomic standpoint, this reflects reduced flexibility between sympathetic activation and parasympathetic recovery.

Rather than transitioning smoothly between alertness and rest (activation and recovery), the nervous system may remain biased toward sustained sympathetic dominance (e.g., tachycardia, hypervigilance, insomnia) or toward compensatory hypoarousal (e.g., exhaustion, shutdown, dissociation).

These are not transient emotional states. They are state-dependent physiological patterns that shape symptom expression across multiple systems.







⋆ exaggerated cardiovascular responses to positional change or mild exertion
⋆ heightened sensitivity to light, sound, temperature, or internal bodily sensations
⋆ rapid onset of fatigue, dizziness, or cognitive “fog” following minimal stimulation
⋆ difficulty returning to baseline after stress, activity, illness, or emotional load


What Dysregulated Sensory Modulation Looks Like Clinically

In conditions such as Postural Orthostatic Tachycardia Syndrome (POTS) and post-viral syndromes (Long-Covid, Lyme disease), symptoms often extend beyond what can be explained by isolated organ dysfunction or structural findings.

Individuals commonly report:

⋆ orthostatic intolerance with disproportionate heart rate increases
⋆ exercise or activity intolerance exceeding expected deconditioning
⋆ sensory hypersensitivity
⋆ post-exertional symptom exacerbation
⋆ fluctuating pain, gastrointestinal disturbance, temperature dysregulation, and cognitive impairment without evidence of acute injury
⋆ exaggerated immune responses (including histamine-mediated reactions, heightened inflammatory signaling, and allergy-like responses that occur without clear external triggers)

Taken together, these patterns suggest a nervous system operating with narrowed regulatory margins, where sensory and interoceptive input more readily triggers protective autonomic responses.

Sensory modulation provides a framework for understanding why these systems remain reactive even when standard diagnostic testing does not indicate active infection or illness,.








Relevance to POTS and Post-Viral Syndromes

In these contexts, symptoms are less indicative of illness or injury and more reflective of altered nervous system regulation.

Following infection, inflammation, prolonged stress, or cumulative physiological load, the nervous system may recalibrate its thresholds for detecting and responding to threat. This recalibration favors protection over efficiency.

As a result:

⋆ sensory signals are amplified
⋆ autonomic responses are initiated more readily
⋆ recovery from stimulation becomes prolonged
⋆ cumulative load leads to symptom escalation

These changes reflect adaptive regulatory responses under sustained demand, rather than pathology localized to a single system. What often goes unrecognized is that this shift can persist even after the original stressor has resolved. 








A Regulatory Rather Than Structural Explanation

Somatic and trauma-informed models conceptualize trauma not primarily as a psychological event, but as a persistent alteration in nervous system organization following overwhelming experience.

Neurophysiological trauma models describe dysregulation within core response networks involving autonomic, limbic, and motor systems (networks responsible for survival, threat detection, and mobilization).

Sensory modulation intersects directly with this framework. In practice, these patterns are often recognizable long before they are measurable. 

When experiences exceed the nervous system’s capacity to respond and recover, (whether due to physical illness, injury, emotional stress, or prolonged overwhelm), the system may adopt long-term patterns of heightened arousal or defensive withdrawal. These patterns influence how sensory information is processed long after the initiating stressor has resolved.

This does not suggest that all chronic illness is trauma-based. Rather, it underscores that regulatory patterning remains clinically relevant regardless of the original cause.








Sensory Modulation & Trauma Physiology

Sensory modulation occupies a gap between disciplines.

It is distributed across systems, difficult to capture through standard imaging or laboratory testing, and often described in differing terms depending on the clinical or research context.

Despite this, its clinical relevance has been increasingly documented. A recent systematic review published in the Australian Occupational Therapy Journal synthesized evidence on sensory modulation interventions in adult mental health settings, highlighting their role in supporting emotional regulation, arousal management, and functional engagement (Sutton et al., 2023).

What is notable is not only the outcomes described, but the assumptions underlying the interventions: that the nervous system’s ability to regulate sensory input is foundational to stability, participation, and recovery.

This premise aligns with broader findings in autonomic and trauma physiology, yet remains under-integrated in chronic illness care.








Why This Has Been Under-Integrated in Clinical Care

For medical professionals, a sensory modulation lens:

⋆contextualizes multisystem symptom presentations
⋆accounts for variability and flare patterns without psychologizing
⋆complements structural and biochemical models of disease

For individuals living with chronic illness, it offers:

⋆a coherent explanation for symptom sensitivity and fluctuation
⋆a framework that reduces self-blame
⋆a rationale for interventions that prioritize reducing physiological load rather than increasing effort

This perspective does not replace medical evaluation or treatment. It adds a regulatory dimension that helps explain why symptoms persist even when conventional markers are stable.









CLINICAL AND LIVED IMPLICATIONS

The framework presented here reflects an integration of peer-reviewed research, cross-disciplinary theory, and clinical observation. While sensory modulation is well established within occupational therapy and mental health literature, its application to chronic illness, post-viral syndromes, and autonomic dysregulation remains limited in mainstream medical models.

The interpretations offered are informed by existing literature, observations from my work with a limited but consistent demographic, and my own lived experience navigating chronic illness and recovery. This work is not intended to replace medical diagnosis or treatment, but to offer a regulatory lens for understanding persistent, multisystem symptoms where conventional explanations fall short.










Author’s Note on Scope and Interpretation

Sutton, D., Nicholson, E., Wilson, M., & Vanderpyl, J. (2023). Sensory modulation interventions in mental health: A systematic review. Australian Occupational Therapy Journal.
 https://doi.org/10.1111/aphw.12554

Champagne, T., & Stromberg, N. (2004). Sensory approaches in inpatient psychiatric settings: Innovative alternatives to seclusion and restraint. Journal of Psychosocial Nursing and Mental Health Services, 42(9), 34–44.

Sutton, D., Wilson, M., Van Kessel, K., & Vanderpyl, J. (2013). Optimizing arousal to manage aggression: A pilot study of sensory modulation. International Journal of Mental Health Nursing, 22(6), 500–511.

Hassett, A. L., & Clauw, D. J. (2010). The role of stress in rheumatic diseases. Arthritis Research & Therapy, 12(3), 123.

Levine, P. A., & colleagues. (2015). Trauma and stress-related disorders: A neurobiological perspective. Frontiers in Behavioral Neuroscience.

van der Kolk, B. A. (2014). The body keeps the score: Brain, mind, and body in the healing of trauma. Viking.












REFERENCES

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