Puzzling processSurprisingly little is known about how deep brain stimulation works, in spite of the fact that tens of thousands of Parkinson's and other movement disorder patients have been treated with the therapy.
"Right now it's not only not known which cells are the target, but also if they turn [their activity] up or down" in response to the stimulation, says Dr. Karl Deisseroth of Stanford University. "It's that level of confusion."
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In other cases -- for example in treating minimally conscious patients -- deep brain stimulation seems to have the opposite effect to damaging the targeted brain area.