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L-DOPA Challenge Test May Predict DBS Motor Function Response A recent study published in Frontiers in Human Neuroscience suggests that the L-DOPA challenge test prior to DBS surgery may predict motor function response after surgery, depending on whether the implant is in the subthalamic nucleus (STN) or globus pallidus interna (GPi). Although the study was small, the analysis showed a correlation between patients who responded to the test prior to GPi-DBS and improved motor function. There was no correlation between levodopa response and motor function for patients with STN-DBS surgery. However, a better response indicated better non-tremor scores, unlike GPi-DBS implants. Deep Brain Stimulation at Some Frequencies May Be as Effective as Medication for Parkinson's Disease BY CARI WADE GERVIN A NE W STUDY OFFERS HOPE FOR IMPROVING DBS TRE ATMENTS. DEEP BR AIN STIMUL ATION (DBS) has been used for a while for advanced Parkinson's disease to reduce tremors and improve function. While the implanted electrodes seem to work best at a certain frequency range for most patients, it has remained unclear why some frequencies work better than others. Trying to find which frequency works best for which patient can take months. A new study in Nature Communications Biology shows promis- ing results for speeding up that process. The study indicates that therapeutic high-frequency stimulation (130–180 Hz) induces high-frequency oscillations (~300 Hz, HFO) with similar results to medication. "When we played with the frequency, we realized that there's a certain frequency that promotes the high-frequency oscillations and the resonant activity," says Nuri Ince, PhD, associate professor of biomedical engineering, University of Houston. "We believe now this could be a way of fine-tuning the stimulation frequency for individuals and optimizing DBS therapy." PROMISING CLINICAL IMPLICATIONS Ince and his colleagues recorded the response of the brainwaves at the same time as they were stimulating the brain, which a llowed them for the first time to eliminate the amplitude artifacts that mask the full neural response. While the results need to be validated with a larger study, the implications of the new process could change the way Parkinson's is treated, and possibly other neurological conditions. "There's quite an interest from the industry into this scholar- ship because it has huge clinical implications," Ince says. If further studies with subthalamic nucleus DBS continue to be promising, additional research will follow to determine if similar patterns exist with globus pallidus interna DBS. "Other indications such as essential tremor or psychiatric indications and related targets need to be investigated," Ince says. "This will open a new route in terms of research for the optimization of DBS technology advances, as electrodes are becoming more and more complex." n 2 2

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