Tuesday, July 01, 2008

Brain: If a pill did not cause all your problems, chances are a pill won't fix them all either

Charles Barber, Yale Lecturer in psychiatry, provides some much-needed perspective on the usefulness (or not) of functional magnetic resonance imaging and other techniques for surveying the brain in "The Brain: A Mindless Obsession? (Wilson Quarterly, Winter, 2008):
... Brain images are still far cruder than one would think after reading the sensational revelations attributed to them in the science pages of newspapers and magazines. And it must be remembered that these are secondary images of blood flow and glucose in the brain, and not of brain tissue itself. We seem to forget that it is not as if a camera were entering the brain and taking pictures of what is going on. At this point, the most that can be said is that brain imaging indirectly and very broadly measures the activity of groups of thousands of neurons when the brain is engaged in a physical or mental task. While there are some correlations between brain activity in certain regions and external, observable behavior, it is very hard to gauge what the pictures really mean. How does the flow of blood in parts of the brain correspond to feelings, moods, opinions, emotions, imagination? It remains a daunting task to create theories to “operationalize” what is going on underneath all the pretty pictures.

The state of the art right now is that we can read brains—to some very crude extent—but we can’t even begin to read minds. Wall Street Journal science writer Sharon Begley has coined the term “cognitive paparazzi” to describe those who claim they can. “What does neuroscience know about how the brain makes decisions? Basically nothing,” says Michael Gazzaniga, director of the SAGE Center for the Study of the Mind at the University of California, Santa Barbara.

Another limitation of contemporary neuroscience, Gazzaniga says, is that many brain imaging studies are based on averages of the scans of many patients. “The problem is if you go back to the individual scans, you will see wide variation in the part of the brain that’s activated.” And if you were to do the same scans of the same activity a year later, you might get quite different results.

The ultimate indicator of our newfound faith in scientific psychiatry may be the mysterious growth of the placebo effect in tests of the drugs the new psychiatry dispenses. When Columbia University psychiatrist B. Timothy Walsh analyzed 75 trials of antidepressants conducted between 1981 and 2000, he discovered that the rate of response to placebos, which are, of course, nothing more than sugar pills, increased by about seven percent per decade. Simply because people thought they were taking the all-powerful medicines, they thought they were getting better.

So it is still true that getting better is something you do for yourself. It is not something a pack of neurons is going to accidentally do for you.