People with Parkinson鈥檚 disease are getting brain implants that can automatically detect and reduce harmful nerve cell activity, to test if the technique could reduce movement difficulties.
The device is a step up from a conventional brain implant because it is designed to reduce the side effects of this invasive treatment.
Parkinson鈥檚 disease causes worsening tremors and difficulties with movement, especially when initiating actions. Medication can help, but as symptoms progress, some people have a more drastic treatment, called deep brain stimulation (DBS).
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This treatment works by placing wires into the skull that deliver a current to dampen down the activity in clusters of nerve cells in the centre of the brain. This can cause side effects, such as speech difficulties and jerky movements.
It may be possible to minimise these side effects by delivering stimulation only when it is needed, known as responsive stimulation. Nerve cell activity can be recorded either from the same wire that delivers the current or a second one.
A similar kind of brain implant is already used in a few people with severe epilepsy that is unresponsive to medicines or surgery, to reduce the excessive nerve cell activity that causes seizures. But in people with Parkinson鈥檚 it is less clear what kind of brain activity causes the different symptoms and side effects.
Brain wave targets
One area of interest is the nerve cell clusters deep in the brain targeted by the brain implants. In most people, these centres sometimes fire in synchronous patterns called beta waves to signal that we should continue our present behaviour, whatever that is. 鈥淚t promotes the status quo,鈥� says Peter Brown at the University of Oxford.
In Parkinson鈥檚, there is an excess of beta waves, and this could explain why people with the condition sometimes move more slowly than they want to and have difficulties initiating new movements. So Brown and his colleagues are trying to stimulate the nerve cell clusters only when beta waves are detected.
The team tried the technique in 13 people with Parkinson鈥檚 who had a particular problem with moving too slowly, while they were having surgery under a local anaesthetic to replace the battery of their existing DBS implant. Brown鈥檚 team found that the than conventional constant stimulation, and it was about as effective at combating slow movements.
鈥淧roblems with speech are currently one of the most problematic side effects of standard DBS, says David Dexter at charity Parkinson鈥檚 UK. 鈥淭his can have a huge impact on quality of life.鈥�
However, responsive stimulation led to the recurrence of their tremor in two patients 鈥� so the approach might not be suitable for everyone. Tremor may be caused by problems in different nerve clusters, says Brown.
Tim Denison at the University of Oxford, who wasn鈥檛 involved in the study, is trying to develop another kind of responsive DBS that targets the other main side effect of DBS, involuntary jerky movements. By introducing a second wire on the surface of the brain, his team has found that these movements are accompanied by another kind of brain wave 鈥� gamma waves 鈥� in an area called the motor cortex.
He hopes that in future, people could have their DBS activity turned down automatically when gamma waves are detected. 鈥淭his is where the field is heading,鈥� says Denison.
A team led by Aysegul Gunduz at the University of Florida is also carrying out a 20-person trial for a kind of responsive stimulation in people who already have
Reference: bioRxiv,
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