Research Spotlight: Understanding and Tackling Freezing of Gait — My Research, one step at a time…
For many people living with Parkinson’s disease, movement can feel like a dance with an unpredictable partner. One of the most frustrating challenges is freezing of gait—that sudden moment when your feet feel glued to the floor even though your mind is telling you to move. I’ve spent much of my career trying to understand why this happens and, more importantly, how we can help people overcome it.
I’ve met hundreds of people who describe the same distressing experience: “My feet just won’t move, even though I’m trying.” Freezing of gait steals independence, confidence and quality of life. For me, conversations with patients and their loved ones in the clinic have always been the driving force for the research that I undertake. What became clear to me pretty early on, was that freezing of gait isn’t an isolated physical (motor) symptom, there is much more at play. It has a wide range of different triggers like turning, passing through doorways, dual-tasking (‘walking and chewing gum’) and periods of heightened anxiety. Thus, my research into freezing was initially guided by one key question: what is happening in the brain when voluntary movement suddenly stops?
How It All Began
I started studying freezing of gait after being provoked by an ‘argument’ I was having with Adrian Owen, one of my mentors at the University of Cambridge who is now most famous for his seminal work understanding consciousness. I had just completed my research thesis, which had used functional MRI (fMRI) to explore what was going on in the brain when people with Parkinson’s disease were struggling to perform working memory tasks. It was a great publication, but I couldn’t see how it was going to help solve this problem! Adrian, who obviously could see far better than I that this finding would allow people to design better ways of measuring the impact of novel treatments, calmly asked: So, what symptom do you think you could help fix? I really hadn’t given it much thought but replied instantly: Freezing of gait! Adrian rolled his eyes and said: Good luck with measuring walking inside a 1 tonne MRI scanner. On my journey home, I wondered if I could ‘trick the brain’ using virtual reality in one of those ‘shoot them up’ first person arcade games. Perhaps, using foot pedals to walk through a virtual environment, we could probe triggers like turning, dual-tasking and anxiety and use simultaneous fMRI to record the brain’s activity…
There was one slight problem… I knew nothing about video games, how they worked and how to break inside them to be able to make them do what I needed. I started researching and got pretty far along with making the environments I wanted, but I needed help. My next move was bold, some might argue reckless, but I logged into a chat room for software programmers who thrive on this stuff. I posted a provocative message that read: I have never played one of these games, but I think I might have found a really good use for them… Within an hour, I had found someone who could provide me the solution I required, and the rest as they say, is history... This individual has never craved attention or reward but has bought in to trying to help people living with Parkinson’s. It is truly wonderful and awe inspiring to know that our community extends beyond what we think we know!
Studying the brain in real time
As I began to think about what was actually going on in the brain during a freeze, it struck me that to walk effectively and juggle all of the ongoing demands like turning, dual-tasking and anxiety meant a lot of information having to be processed in parallel through a part of the brain that is most impacted by the dopaminergic loss associated with Parkinson’s. One of the other features, I recognised was that if patients could focus their attention on breaking the freeze or external cues (e.g. lines on the floor or a ticking metronome) they could restore or maintain their walking. This led to a testable hypothesis that we could potentially use fMRI and other modalities like brain wave recordings (electroencephalography – EEG) and the firing patterns of brain cells from the deep brain stimulation (DBS) electrodes to confirm.
Virtual Reality (VR) combined with fMRI was a game-changer in my research. For the first time, we were able to confirm my hypothesis and observe the neural correlates of freezing. I was very grateful for the support we received from the Michael J Fox Foundation who told me at the time that it was the craziest idea that they had ever heard! Since then, we have demonstrated the basis for freezing related to turning, dual-tasking, doorways and anxiety. Subsequently, we have used the VR in the operating theatre to record from the deep structures in the brain, which demonstrated a signal occurring at least two seconds before the feet come to an abrupt halt. This research also predicted that we would be able to use EEG to predict freezing in patients walking in the real world.
So, what about improving treatment?
My finding that attention plays a key role in the phenomenon of freezing led to our randomised control trial that demonstrated improvements following a program of cognitive training, work again supported by the Michael J Fox Foundation. The results from our EEG and DBS studies has led to the concept of biofeedback where if in real time, we could predict the onset of freezing before it occurs, we might be able to change the future. For example, if patients wearing non-invasive EEG (like a light headband) could be given an on-demand cue, like a metronome tick or a projected line on the floor, patients might be able to abort the freeze. The advances we are seeing in DBS are also very promising and the hope is that if such systems could sense the freezing signal, it might be possible, through adaptive DBS systems, to change the stimulation settings and maintain safe walking. Whilst not currently available, these systems are in development. Finally, our work has highlighted that dopamine isn’t the whole story when it comes to freezing. The condition involves several neurotransmitters—especially noradrenaline, serotonin, and acetylcholine—that influence attention, arousal, and executive control. This is allowing us to explore novel medication strategies that target these systems. In collaboration with Jorik Nonnekes and Kaylena Ehgoetz Martens, funded by the Michael J Fox Foundation and Shake it Up Australia, we will be attempting to target noradrenaline with a repurposing strategy in a trial we are calling Anti-Freeze.
These studies are still evolving, but they show promise. My hope is that, in the future, we can offer truly personalised treatment plans that target each person’s unique pattern of symptoms—rather than a one-size-fits-all approach.
Looking Forward
The future of Parkinson’s research is incredibly exciting, and research is a team effort. I am proud to work alongside so many talented scientists, clinicians, and—most importantly—patients and carers. Together, we’re not just studying Parkinson’s; we’re changing what it means to live with it.
Learn more about my work about freezing please visit: https://www.profsimonlewis.com/?s=freezing
Professor Simon Lewis is based at Macquarie University in Sydney Australia. He has attended and spoken at many past World Parkinson Congresses. He is part of the WPC Research Spotlight 2026 Series and will be talking about his work above on Freezing of Gait on January 27, 2026 at 11AM ET. Learn more and register at https://www.worldpdcoalition.org/page/WPCResearchSpotlight
Ideas and opinions expressed in this post reflect that of the authors solely. They do not necessarily reflect the opinions or positions of the World Parkinson Coalition®