Healing our Brains, Changing our Selves?

Drugs used to treat another neurological disorder, Parkinson’s disease, have been linked to more arresting personality changes. In people afflicted by the disease, a large portion of the brain cells that produce dopamine, a chemical used by the cells to communicate with each other, die off for unknown reasons. The first symptoms are increasingly jerky movements and tremor, and later dementia can arise.

In 2005, doctors from the Mayo Clinic in Rochester, Minn., described 11 people with the disease who had developed pathological gambling habits after taking dopamine-like medication. One patient, a 50-year-old married man who had never gambled before, began spending all his time at casinos, saying he felt unable to pull himself away from the tables. When he wasn’t gambling, he was drinking and eating excessively, and he started having sex with his wife four times daily instead of only once a week. When the doctors stepped down his medication, he stopped gambling as suddenly as he had begun, and returned to his normal sex life.

“The drugs used to treat Parkinson’s can cause behavioral side effects in about 10 or 15 percent of people,” says Dr. Curt Freed, director of the Neurotransplantation Program for Parkinson’s Disease at the University of Colorado. Partly because the drugs stop working in the long run, and partly because of their side effects—including serious movement disturbances—Freed began transplanting fetal dopamine cells deep into the brains of his patients in the late 1980s. If he could confine the new cells to the small movement-related area that needed dopamine, the treatment might have fewer side effects than a drug that bombards the entire brain.

“We did cognitive testing before and after the transplant,” says Freed, “and there was no hint of any effect on cognitive function or emotional state, depression and that sort of thing.” He adds that avoiding behavioral and psychological side effects is a matter of scientific know-how. “We understand the brain areas that are responsible for different functions, so I would argue it’s not a philosophic issue but a target issue. You don’t have to say, ‘Oh my goodness, if we put in new cells is this person going to become somebody different?’—you’d have to have that as your goal.”

The transplants weren’t perfect—they only worked in people who responded to dopamine drugs and even then didn’t completely bring them back to normal—but “for most patients they can relieve the most severe symptoms and provide a reservoir of dopamine for the patients,” Freed says. He is now working on converting stem cells into dopamine cells for transplantation, because the supply of fetal cells in severely limited.

But the limited size and function of the area targeted in Parkinson’s disease present a special case. In Batten disease, for instance, stem cells have been injected at multiple sites in the cortex, and the psychological consequences remain unknown.

In most cases, though, they would probably be a small price to pay if the treatments turn out to be successful. “But at the same time, folks should know about [the psychological side effects],” says Mathews of Hopkins. “We want people to make a fully informed, autonomous choice.”

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