So far, the researchers have tested the device in animals and are now working on making similar dopamine sensors appropriate for human use. They ultimately hope to combine the stimulating and sensor electrodes into a single implantable electrode with separate regions for chemical recording and electrical stimulation. "Our long-term goal is to expand the usefulness of new DBS devices in the treatment of a range of neuropsychiatric disorders," says Charles Blaha, a professor of experimental psychology at the University of Memphis, who is leading the animal work on electrically evoked neurotransmitter release.

Aside from improving the surgery, a device that measures neurotransmitters directly in the brain could shed light on exactly how DBS works and help doctors better understand the intricacies of the brain. "The ability . . . to detect neurotransmitter changes in the brain will help us understand the mechanisms by which the stimulation works, and help us understand the disease process better," says Rezai. However, he cautions that the technology needs to be further developed for use in humans.

One concern is that adding additional probes into the brain could result in tearing of the brain tissue. Steven Schiff, a pediatric neurosurgeon and director of the Penn State Center for Neural Engineering, adds that the value of chemical information from neurotransmitters should be demonstrated, to see if it would improve electrode placement and the outcome from DBS. However, he says that using electrodes to measure neurotransmitters "is extremely exciting for the future. You cannot measure these analytes from traditional electrical recordings, and thus very important variables from the functioning of the nervous system go unobserved otherwise."