The complexity of the brain -- in which nerves project in all directions and connect with one another to form multiple, looping networks -- makes studying how deep brain stimulation works a challenge, Grill said.
Grill's team created a mathematical model of a normally functioning brain cell. The researchers then gave the model neuron the pathological pattern of activity seen in people with tremors, assembled a group of these model cells and watched what would happen when the cells were electrically stimulated at various rates and intensities.
In addition to showing how the therapy works, their model of neurons in action also revealed that stimulation delivered at too slow a pace fails to keep bad information at bay. Indeed, slower pulses can actually add to problematic bursts, they showed.
The model's findings closely parallel the clinical responses of patients, who typically experience the greatest relief from symptoms when their devices are tuned by physicians to deliver rapid pulses, Grill said. Patients' symptoms can actually worsen when the devices are dialed to a slower setting.
The intensity of stimulation also plays an important role, the study suggests, by determining the number of brain cells affected by a particular series of pulses.
A better understanding of the processes underlying deep brain stimulation could enable physicians to better fine-tune electrical implants, Grill said. That could be particularly useful for zeroing in on effective settings for implants used to treat diseases, such as epilepsy, in which seizures occur only sporadically, as well as conditions, such as depression, in which symptoms can vary widely from day to day.
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