COURTESY OF CORALIE DE HEMPTINNEStimulate the brain of a patient suffering from Parkinson’s disease (PD) via a surgically implanted electrode and there’s no mistaking the results: the person’s slow movement, tremor, and/or rigidity—common symptoms of the neurodegenerative disorder—all but disappear immediately. When the device is turned off, the motor symptoms return in full force. But how deep-brain stimulation (DBS) effects such changes has been unclear.
In a study published yesterday (April 13) in Nature Neuroscience, researchers at the University of California, San Francisco (UCSF), uncovered evidence to suggest that DBS works by reducing the overly synchronized activity of the motor cortex, which controls the body’s skeletal muscles.
Two years ago, UCSF neurosurgeon Philip Starr, postdoc Coralie de Hemptinne, and their colleagues had identified extremely synchronized neural activity in the cortex as a common factor in the Parkinson’s brain. For the new study, the researchers temporarily placed a strip of six recording electrodes over the motor cortex of 23 Parkinson’s patients during surgery to implant a permanent DBS electrode. Over the course of the six-hour surgery, during which patients are awoken to ensure the proper placement of the DBS electrode, “we measured synchrony in the motor area of the brain before, during, and after DBS, and while the patient was resting or engaged in a movement task in which they had to reach and touch a computer screen,” de Hemptinne said in a press release. The results showed that as soon as the DBS electrode was switched on, stimulating the subthalamic nucleus (STN) deep in the brain, the activity of the motor cortex quickly became less synchronized. When the device was turned off, the synchronicity returned.
Whether this reduction in synchronicity is the cause of DBS’s potent effect on Parkinson’s symptoms remains to be seen, however. “There are many biological changes that have been associated with deep brain stimulation,” University of Florida neurologist Michael Okun, who was not involved in the study, told MIT Technology Review. While synchronization of brain rhythms could be one factor, “we should be very cautious about overinterpretation.”
To better understand what’s going on during DBS treatments, Starr’s group has teamed up with medical device company Medtronic to implant DBS devices that can simultaneously record activity in the motor cortex, allowing the researchers to collect long-term data on how DBS affects brain activity. “Now we can try to find even better correlations between DBS and symptoms, and we can even look at the effects of medications,” de Hemptinne said in the release. “This new ability to collect data over a longer time course will be very powerful in driving new research.”