How deep brain stimulation works for Parkinson’s Disease

Alleviating Parkinsons through deep brain stimulation from Science News on Vimeo.

Deep Brain Stimulation (DBS) is mostly used for Parkinson’s Disease. DBS for Obsessive Compulsive Disorder and Depression is just starting to be used. It is unclear how DBS works for Parkinson’s Disease. With DBS an electrical probe is inserted into the brain and it stimulates an area known as the subthalamic nucleus. This can help people with Parkinson’s disease overcome the disorder’s neurological block on movement.

But how does this stimulation work. Some researchers think the technique stimulates neurons that initiate movement. Others say it blocks inhibitory neurons, allowing brain signals to resume. And yet another theory holds that it influences the flow of information along axons — fibers that connect neurons to each other.

A recent study published in Science shows that deep brain stimulation exerts its effect on axons, specifically those that feed into the subthalamic nucleus, rather than on the neurons in the structure.

This is the experiment:

For the Science study, the team genetically engineered mice that have a condition that mimics Parkinson’s disease to produce light-responsive proteins only in certain cells in the brain. Then, the researchers inserted fiber optic threads into the mice’s brains. The team used a pulse of blue laser light to increase activity of the cells, or a burst of yellow laser light to quiet the cells. The scientists also used electrical probes to measure activity of the neurons.

When the researchers turned on the light in cells in the subthalamic nucleus nothing happened. But light stimulation of incoming axons improved the mice’s movements. Quieting activity of the axons made the movement disorder worse.

These findings sugests that to stimulate parts of the brain closer to the surface might be an alternative to deep brain surgery. This is a less invasive procedure than DBS.

In yet another Science publication the stimulation of the spinal cord in mice and rats could restore movement to rats and mice with Parkinson’s–like problems.

It’s good news for patients,” says Feng, who was not involved in either study. “Of course, it is not a cure.”

He says that the light-responsive techniques may help uncover the neural circuitry that leads to other psychiatric diseases, such as depression and obsessive-compulsive disorder, which are also sometimes treated with brain stimulation. And spinal cord stimulation or other minimally invasive therapies may offer psychiatric patients an alternative to deep brain surgery.

This will be continued but it will not stop the use of DBS for Parkinson’s disease and why should it, we don’t know how antidepressants work or ECT for that matter.

Thanks Science News
Gradinaru, V., Mogri, M., Thompson, K., Henderson, J., & Deisseroth, K. (2009). Optical Deconstruction of Parkinsonian Neural Circuitry Science DOI: 10.1126/science.1167093
Fuentes, R., Petersson, P., Siesser, W., Caron, M., & Nicolelis, M. (2009). Spinal Cord Stimulation Restores Locomotion in Animal Models of Parkinson’s Disease Science, 323 (5921), 1578-1582 DOI: 10.1126/science.1164901