Neurons slow down for placebo effect

Inert substances used as sham medications, or placebos, temporarily benefit some people with Parkinson’s disease by easing the activity of brain cells that contribute to their condition, according to a new trial.

A research team led by Fabrizio Benedetti of the University of Turin Medical School in Italy first gave 11 Parkinson’s patients injections of a medication that briefly quelled muscle rigidity and related symptoms. The drug, apomorphine, raises brain concentrations of dopamine, a brain-signal transmitter.

After the drug’s effect had worn off, the researchers temporarily inserted a hair-thin electrode into each volunteer’s brain to measure electrical signals emitted by cells in a Parkinson’s-implicated area called the subthalamic nucleus. As expected, all the patients exhibited excessive neural activity in this region.

These same people then received a placebo injection of a salt solution that they believed was apomorphine. In six of the patients, Parkinson’s symptoms temporarily improved and electrical activity in the subthalamic nucleus declined markedly and occurred at a more even pace than it had before the volunteers received the placebo. The five people who gained no relief from their symptoms after the placebo injection exhibited no neural change.

The results, published in the June Nature Neuroscience, elaborate on preliminary evidence that placebos may aid individuals with Parkinson’s disease (SN: 9/15/01, p. 175: Available to subscribers at Placebos are dead, long live placebos).

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.