Scientist Interview: Implanted Electrodes Reboot
Brain out of Intractable Depression

Scientific American - Gary Stix, 10/03/13

An image that surgeons use to prepare for implanting a deep brain stimulator (enlarged here) in the medial forebrain bundle, nerve fibers involved in depression

Deep brain stimulation refers to the implantation of very small electrodes in both hemispheres of the brain, which are connected to a neurostimulator, usually placed under the skin on the right chest. This device is in size and function very similar to a heart pacemaker. It allows stimulations of different pulse width and frequency. Depending on the chosen stimulation parameters the electrodes in the brain are able to “neuromodulate” – to reversibly alter the function – of the surrounding brain tissue. Deep brain stimulation has gained widespread acceptance as a successful treatment for tremor associated with Parkinson’s disease. More than 80,000 patients worldwide have been treated with this method. Some see deep brain stimulation as a much less invasive and fully reversibly alternative to historical neurosurgical interventions, which require tiny amounts of brain tissue to be destroyed in order to have clinical effects.

About three years ago we started to get interested in the medial forebrain bundle as the key input structure of the reward system together with Dr. Volker Coenen, a functional neurosurgeon, who has been looking at this system already for a longer time. The medial forebrain bundle projects from the ventral striatum area through the nucleus accumbens to the prefrontal cortex. In a study using diffusion tensor imaging (DTI), a method which displays fiber structures in the living brain, we were able to demonstrate that all three currently used targets for DBS in depression are either in close topographical relationship or overlap fibers of the medial forebrain bundle.

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