Quick answer: Researchers compared 36 people with FND and 42 people without it. Brain recordings showed a difference in how the groups used heartbeat signals to predict sounds. This is not a diagnostic test, a cause of every symptom, or a treatment.
Why can someone move normally one moment and struggle the next? And why, when the symptoms are so real, can a routine scan appear normal?
A scientific study published on 7 October 2026 in the journal Psychophysiology may help researchers get closer to one of the mechanisms involved.
Researchers in Switzerland found measurable differences in how the brains of people with FND processed and predicted signals coming from within their own bodies.
This is not a cure, and it is not a complete explanation of FND. It is another careful contribution to a condition that has been misunderstood for far too long.
What the researchers actually found
The study is called Altered Interoceptive Predictive Coding in Functional Neurological Disorders. It asked how the brain uses internal bodily signals when it predicts what will happen next.
The scientists compared two groups: 36 people diagnosed with FND, and 42 people without FND, matched for age and sex. They used EEG to measure electrical activity in the brain, and they recorded participants' heartbeats at the same time.
People with FND did not show the same pattern of brain activity as the comparison group when the researchers tested how the brain used heartbeat-related information to predict sounds.
That suggests some of the processes the brain uses to interpret internal bodily signals, and to make predictions from them, may work differently in FND. The difference was measured in brain activity. It did not rest only on someone describing their symptoms.
Your brain is constantly making predictions
To see why this matters, it helps to understand predictive coding. The name sounds technical. The idea is straightforward.
The brain does not simply wait for information to arrive. It keeps predicting what is about to happen, using previous experience and the signals coming in from the body and from the world around you.
When you pick up a glass of water, the brain predicts how heavy it will be, how much force the fingers need, and how the arm should move. Much of that happens automatically.
At the same time, the brain is processing internal signals, including heartbeat, breathing and other bodily sensations. That internal processing is called interoception. It is part of how the brain monitors what is happening inside the body.
Researchers are asking what happens if the way the brain combines those internal signals with its predictions is not working as expected. That is one of the mechanisms under investigation in FND.
How the scientists tested this
The experiment used people's heartbeats and sounds played through headphones.
Some sounds were timed to follow the participant's heartbeat. Others followed a timing pattern that was not synchronised with that heartbeat. Occasionally, an expected sound was deliberately left out.
The scientists then measured how the brain responded to the missing sound. When the brain has learned to expect something, its response to the thing that does not happen can show how it is making predictions.
In the group without FND, brain activity differed depending on whether the sounds had been synchronised with the heartbeat. In the FND group, that same difference was not detected in the main EEG analysis. Further analyses also found differences in the distribution and strength of the electrical activity.
The findings suggest that people with FND may use internal body signals differently when predicting events around them. They do not mean every person with FND has the same difference. They are not a diagnostic test.
A region called the insula
One finding involved the insula. The insula helps the brain process signals from inside the body, and it contributes to bodily awareness.
Using mathematical modelling of the EEG recordings, the researchers identified this region as the most likely source of some of the differences between the two groups. In simple terms, brain networks involved in interpreting internal bodily information may respond differently in people with FND.
The insula was identified by estimating the source of the EEG signal. The researchers did not directly measure that region with a scan. Further investigation is needed. The finding still adds to research on FND, body awareness, and how the brain brings information together.
Could this help explain FND symptoms?
Possibly. This is also where the research must not be stretched further than it goes.
FND can involve symptoms such as:
- Functional seizures
- Tremor and involuntary movements
- Weakness or paralysis
- Changes in sensation
- Difficulty with movement and coordination
- Changes in speech
- Cognitive difficulties and episodes of dissociation
Researchers have proposed that difficulty bringing internal bodily signals together with other information might contribute to some symptoms, particularly movement, sensation, and the sense of control over the body. The study's authors also discuss how these processes could relate to dissociation.
This research did not show that altered predictive coding directly causes these symptoms. It did not establish why any one person has the symptoms they have. It offers evidence for one possible neurological mechanism inside a much more complex condition.
Why this research matters
For many people living with FND, the hardest part is not always the symptoms. It is the disbelief.
Being told there is nothing wrong because a routine scan is normal. Having symptoms questioned because they change through the day. Feeling that other people assume the condition must be imaginary because medicine cannot yet explain every mechanism behind it.
Research like this matters because it keeps investigating what is happening in the nervous system. FND is a genuine neurological condition. As NHS inform explains, it involves difficulty in how the brain receives and sends information, and that difficulty is not under a person's conscious control.
Studies that measure differences in brain activity help scientists look at these processes in more detail. FND symptoms are real, whether or not a particular scan or research test can detect the mechanism behind them. People living with FND should not have to wait for another scientific paper before their experiences are believed.
Does this mean better treatment is close?
The research gives a useful direction for further work. It is not a treatment breakthrough.
Understanding how the brain processes internal bodily information could eventually help researchers look at more targeted approaches to assessment and treatment. This study did not test a treatment. It did not show that the differences can be reversed. It did not create a way to diagnose FND.
There are limits worth stating plainly.
- The study involved 78 participants. That is a relatively small sample.
- The researchers noted possible influences from medication, fatigue, and the timing of the experiment.
- Some findings were not the same when they analysed only the participants who were not taking medication.
- The analyses were exploratory. The results need to be tested again in further research.
Those limits do not make the research unimportant. They show what can reasonably be concluded from it.
What this means if you are living with FND
It does not mean you need to start monitoring your heartbeat, change your medication, or try to retrain your brain on your own.
It also does not mean that every symptom, or every new neurological event, should automatically be put down to FND. New or significantly different symptoms still need a proper medical assessment. Sudden confusion or disorientation needs emergency medical help. If you are unsure whether a change is an FND flare up or an emergency, use urgent care rather than waiting it out.
What this research does offer is another piece of evidence that the nervous system may be functioning differently in FND. For people who have spent years trying to get answers, a carefully conducted study is worth having.
Our thoughts at FND Connect
Understanding should come before judgement.
People living with FND experience genuine, sometimes life-changing neurological symptoms. They deserve to be listened to, supported, and taken seriously.
Good science matters too. That means welcoming a promising finding without presenting an early result as settled fact.
This study does not explain everything about FND. It does not give us a cure. It does not tell us why two people with the same diagnosis can have completely different symptoms.
It does give researchers another measurable difference to investigate. Every step towards understanding FND is a step towards a future in which fewer people have to fight to be believed.
Research and references
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Primary study. Stoffel, N., Mouthon, M., Pelentritou, A., von der Weid, L., Concetti, C., De Lucia, M., and Aybek, S. (2026). Altered Interoceptive Predictive Coding in Functional Neurological Disorders. Psychophysiology, 63(10), e70417. First published 7 October 2026. https://doi.org/10.1111/psyp.70417
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NHS inform: functional neurological disorder. NHS Scotland. Explains FND, its symptoms, diagnosis, and the current understanding of brain function. nhsinform.scot
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A framework for understanding the pathophysiology of functional neurological disorder. A 2021 review in CNS Spectrums of interoception, predictive processing, attention, and other brain networks in FND. PMC7930164
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NHS: sudden confusion. Why sudden confusion or disorientation needs immediate medical attention. nhs.uk/symptoms/confusion
For more on living with FND, read what functional neurological disorder is, or browse FND symptoms in the symptom library.
This article is published by FND Connect CIC for information and awareness. It is a plain-English reading of published research, not an original research paper and not a substitute for medical advice.