Because the neural circuitry of the brain operates via electro-stimulation, applying small amounts of electrical current to the scalp (transcranially) has been investigated as a means of modulating brain activity.
Their findings provide direct evidence that helps answer some of the long-standing, daunting questions in the field.
Then, Feng recognized a novel opportunity to directly measure whether tDCS generates EFs in deep brain areas among patients with movement disorders such as Parkinson's disease, who are often treated by implanting DBS electrodes.
"These patients provide a natural experimental model that gave us a chance to use their implanted electrodes to record how much externally applied tDCS current actually reaches the thalamic and subthalmic regions," says Feng.
First, electrodes are inserted and the patient is sent home for one to two weeks while they stabilize.
Feng's team cleverly took advantage of a 15-20-minute window during the second surgical procedure, before the surgeon connected the battery to the electrodes, to connect the electrodes to a recording device while applying the direct current through the scalp at different current levels using two different montages (pad placements).