In Parkinson’s patients, certain brain cells die off. A “brain pace-maker” activates the affected areas and can alleviate the patients’ symptoms.

Over 500,000 Europeans suffer from Parkinson’s disease and this number continues to rise as the European population grows older. The symptoms of Parkinson’s disease include tremors, rigidity, slowed movements and a shuffling gait, caused by the dying off of brain cells that produce the neurotransmitter dopamine. We still have no lasting cure for the disease.  

Recently a new type of therapy was developed. Patients with especially severe and treatment-resistant Parkinson’s disease can be fitted with a “brain pace-maker.” The so-called deep brain stimulation (DBS) technique uses an electronic implant that sends impulses to the neurons in the brain region affected by the disease, the subthalamic nucleus, employing the same microelectrodes routinely used in animal experiments. DBS could be developed thanks to research on rhesus monkeys. More than 30,000 Parkinson’s patients have already experienced lasting improvement in their quality of life thanks to DBS. To see a working pacemaker watch the movie of Mike Robbins, who suffers from Parkinson’s Disease. He explains how a ‘pacemaker’ implanted into his brain – a surgical technique called deep brain stimulation (DBS) – can help to control his symptoms.  

DBS continues to be refined. Early in 2009 a new treatment was announced that led to marked improvement in rodents with Parkinson-like symptoms. With this new method, the dorsal columns of the spinal cord are stimulated instead of the subthalamic nucleus. Before the new technique can be used in humans, scientists are planning to test it on primates to prove its feasibility and safety.  

The treatment of therapy-resistant depression, obesity and schizophrenia is also possible with deep brain stimulation. Unfortunately, the overall risks associated with all these stimulation techniques are anything but negligible. A recent study reports that 40 percent of all DBS-treated patients experience a multitude of serious adverse events, the most common being surgical site infection, device-related complications, psychiatric disorders, and nervous system or cardiac disorders.  

In part, these problems originate from the fact that the microstimulation method still faces two fundamental challenges: (a) we do not always know exactly what is being stimulated when we pass currents through the tissue, and (b) electrical stimulation causes activation in large areas even outside the stimulation site, making it difficult to isolate and evaluate the behavioral effects of the stimulated area itself.  

Recently, our laboratory developed and optimized the microstimulation method for experiments in anesthetized and behaving monkey whose brain activation is mapped with functional MRI at the same time that the brain is being electrically stimulated. This combined methodology is being optimized in collaboration with the University of Tübingen for application in human deep brain stimulation.