New tools are enabling neuroscientists to break therapeutic ground against daunting disorders like Parkinson’s Disease (PD). Andres Lozano is one “of a small group of heroes,” in Ann Graybiel’s estimate, whose work is yielding astonishing advances on a variety of fronts. Treatments for PD, a progressive, degenerative brain disorder, have until recently dealt primarily with the loss of dopamine-releasing neurons, leading to the classic movement disorders associated with PD: tremor, rigidity, akinesia. But Lozano says that by the time these physical problems are diagnosed, “the reality is that the disease started 10-15 years earlier,” and has involved other brain areas. Lozano determined to focus on three such non-motor symptoms of the disease — gait and posture, depression (in PD and other patients), and cognitive disorders -- and if possible, “reach these circuits, intervene and help patients.” PD patients have serious problems controlling balance and posture, and animal studies helped pinpoint an area in the brainstem responsible for these functions. Lozano got permission to plant electrodes in humans in this area, and mapped out the sensitivities of neurons to voluntary movements such as flexing an ankle or walking. In six PD patients, Lozano sent a mild electric current into these neurons. He shows videos demonstrating the remarkable improvement in control (a patient pushed no longer falls) with deep brain stimulation (DBS). A serendipitous offshoot of this therapy is that it improves REM sleep, in which PD patients are deficient. Lozano has been working as well on mapping and targeting areas of the brain involved in depression, which he has found to be hyperactive. He labeled neurons that responded exclusively to sad and disturbing images, and using DBS, he was able to “turn down the hyperactivity,” successfully reversing severe depression in 60% of his 36 subjects. His final accomplishment emerged by accident: While attempting to treat a patient’s mor...