With our ageing population becoming ever larger, progressive neurological conditions that affect the brain (neurodegenerative diseases) are going to become an increasing challenge for clinicians and society. These neurodegenerative diseases have a variety of presentations and often encompass physical, cognitive and psychiatric symptoms.
Parkinson's disease (PD) is one of the most common of these conditions, affecting 1 in 1000 people over the age of 65. It is characterised by physical symptoms but is also known to significantly affect memory and mood. One of the striking features of the disease is its impact on walking, or gait. Patients are slow and shuffling and may also experience a particular symptom known as Freezing of Gait, where they become unable to walk for no apparent reason. This symptom is highly disabling and also increases the risk of falling with subsequent injury in those individuals it affects.
Using the Virtual Gait Laboratory (VGL) we are attempting to understand the cause for these symptoms of Freezing, which we hope will lead to clinical advances that will benefit patients and 'Defrost Parkinson's Disease'.
The Virtual Gait Laboratory has been designed so that the actions and events within the virutal world may trigger gait related symptoms in patients with PD.
Participants in the research programme are asked to use a foot pedal device to simulate walking in a virtual three-dimensional environment, visualised from the first-person perspective. This activity takes place within an fMRI scanner, with brain activity recorded during the test.
Each left or right pedal corresponds to taking a step forward using the corresponding leg. Visual and audible cues are presented to instruct the participant to either walk or stop. An example session can be seen in this video:
Download Video (wmv, 134MB).
Above, the subject is "walking" through an environment which contains gaps and doors of different widths, as well as left and right turns. The coloured cues used in this example are designed to place additional congnitive load on the subject. Congruent cues (e.g. "BLUE" written in blue) indicate that the subject should continue walking; incongurent cues (e.g. "BLUE" written in green) indicate that they should stop.
While the simulation is running various data points are recorded to a file. These include the cues given to the participant, their actions using the pedals and various environmental events. The simulation allows for test paradigms of varying complexity to be combined with a selection of virtual environments, providing fine control over the cognitive load placed on the participant.
Once the test is complete the results capture from the VGL software and the fMRI scanner can be collated and used to identify which events, if any, can be seen to correspond to types of brain activity.
Note that at 1:45 in the video the VGL is switched into "Test Mode". This is a debugging feature to allow the designers of the paradigms to see what state the test is in at any given time. This display is not presented during use by a test participant.
The virtual environment is constructed using idTech4 technology from id Software (Texas, USA). This is achieved by creating a modification ("mod") based on the game Quake 4, the source code for which id Software make freely available for non-commercial use.
For more detail on the creation of the environments see this page.
Dr Simon Lewis read Medicine at the University of Wales, College of Medicine where he developed an interest in research and also undertook an integrated BSc in Human Anatomy. On graduating from medical school he trained in General Medicine and after becoming a Member of the Royal College of Physicians UK he embarked upon Neuroscience research at the University of Cambridge. His research focussed on the cognitive deficits found in Parkinson's disease and he has published a number of scientific papers in addition to completing an MD in this field.
Having concluded his specialist training in Neurology he is now working at the Royal Prince Alfred Hospital in Sydney where he is developing his research interests in neurodegenerative conditions. One of his particular areas of interest relates to the gait disorders found in these diseases. He is hoping to be able to model these disabilities and therefore gain a greater understanding of them, by utilising the 3-d environments afforded by first-person video game engine technology.
Selected publications:
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