The Promise and Perils of Brain Massage

The annals of science are stuffed full of stories about researchers who were trying to achieve one thing and ended up accomplishing something entirely different. Fortunately for both scientists and science writers, the serendipitous find is a cliché that manages to retain its fascination no matter how many repetitions it goes through. That fascination arises from a fundamental truth about science: the more we think we understand, the more there is to know.

Nowhere is this more true than in the field of neuroscience. Over the past few decades, scientists have made great strides in teasing apart the workings of the brain’s structures on a micro level. We now know, to an astonishing degree of detail, how neuronal cell bodies direct basic functions such as breathing, walking, and other motor functions. We can diagram, model, and even predict how the long, thread-like axons projecting from each brain cell carry electrical impulses from one neuron to another. Yet our fundamental grasp of how the brain’s signals operate on a larger scale—how they interact with each other to create the web of ideas and feelings we call experience—is much less robust. Recently, for instance, two separate teams of researchers were testing a technique called deep brain stimulation to treat obesity on the one hand and Parkinson’s on the other. In the process, both teams made discoveries about the nature of memory and personality.

The phrase “deep brain stimulation” can’t help but sound bizarrely risqué, like some kind of sexy, subversive cerebral activity that’s intended to lead to a throbbing intellectual orgasm. The reality of this increasingly common medical procedure can be almost as difficult to wrap your mind around. The therapy involves a neurosurgeon tucking a tiny electrode deep into a particular location within the spongy, yielding tissue of your brain. Once it has been activated, the implant faithfully delivers a brief but intense pulse of electricity to the surrounding tissue, in regular intervals, for as long as it continues to reside there. The treatment has been described by more than one scientist as being a little bit like a “pacemaker for the brain.” Early forms of deep brain stimulation have been around since the 1960s, and the therapy is now used to treat everything from chronic pain to the startling verbal outbursts caused by Tourette’s syndrome.

Researchers have found that short, controlled stimulation of the brain tissue around the electrode can correct for the irregular or dysfunctional signals that are thought to be responsible for symptoms like the chronic muscle tremors and stiffness associated with Parkinson’s disease and multiple sclerosis. But the regular pulsations emitted by these hair-thin electrodes don’t just combat physical manifestations of disease. They seem to be effective in dealing with certain types of emotional and cognitive maladies, too. Some clinically depressed subjects, for whom the heavy veil of melancholy seemed impossible to lift, reported feeling lighter almost immediately after the current was turned on in their implants. The procedure has even helped to quiet the irresistible impulses experienced by patients with treatment-resistant obsessive compulsive disorder.

Despite its disquieting name, deep brain stimulation has proven to be a life-changing therapy for thousands of patients who suffer from otherwise intractable disorders. It’s also been an amazingly rich source of accidental discoveries about how the mind works.

One 2008 study conducted by a group of French psychiatrists, for example, found that some patients who had received years of deep brain stimulation treatments in order to control their Parkinson’s tremors became less able both to experience emotions such as motivation and interest, and to recognize emotions on human faces. These unintended effects of the therapy have helped to confirm that the the subthalamic nucleus of the brain is involved in regulating both motivation and facial emotion recognition.

In 2007, a team of Canadian physicians led by the Toronto Western Hospital’s Andres Lozano used deep brain stimulation on a patient who suffered from morbid obesity. The doctors hoped that receiving a session of deep brain stimulation would help to curb the patient’s appetite, as it had previously been shown to do in animals. Instead they found that the therapy caused the man, who was 50 years old, to experience sudden, vivid recollections of events that had taken place decades ago. They succeeded, in other words, in altering the signals his brain cells were sending to each other—but they failed to entirely predict the kinds of messages these altered signals would end up communicating. While undergoing the treatment, the patient reported that he felt as if he were in the midst of a crowd of old friends, as well as an old girlfriend, in a park—the remembered scene bright with rich color and movement. In addition, longer periods of stimulation enabled the patient to perform better on tests of memory. Lozano’s team published their discovery in the January 2008 issue of the Annals of Neurology, and some scientists speculate that their work may eventually lead to what could be a powerful treatment for people with cognitive disorders, such as Alzheimer’s, which cause memory loss.

That same year, scientists at the University of Arizona made an equally stunning discovery about the effects of brain stimulation on character. The team, led by psychologist Michael Frank, used a computer program that required the user to choose between “good” symbols (those that resulted in positive feedback 80% of the time) and “bad” ones (those that resulted in negative feedback 80% of the time) to study how how Parkinson’s patients who were receiving DBS made decisions. They found that patients being treated with DBS became far more impulsive than those on dopamine medications or healthy control. They couldn’t seem to stop themselves from choosing the bad symbol even when they knew it was likely to produce negative feedback. This impulsiveness was observed in more realistic situations as well. Wrote Frank of the first DBS patient in our study, who happened to be wheelchair-bound, that “when asked whether he might be more comfortable in a different chair situated across the room (he) immediately advanced toward that chair—ignoring the fact that he was not able to walk properly and was likely to fall.” What Frank and his colleagues believe is that by disrupting the electrical activity in an area of the brain known as the subthalamic nucleus, DBS effectively prevents people from taking their time when confronted with two conflicting options for how to behave.

Perhaps what’s most fascinating about both these findings is how directly and reliably the researchers were able to manipulate the experiences their patients were having. In the case of Lozano’s patient, the more current was used in the stimulation, the more details he was able to recall from his happy memory. In the case of the Parkinson’s patients, when the stimulation was removed, their cool-headed decision-making powers seemed instantly to return. Although it may seem presumptuous to interfere in such a direct and palpable way with the brain signals that control our thoughts, memories, and emotions, it’s worth remembering that the medications many of us take without much thought—and the meditation sessions many use to calm their thoughts—have precisely the same intent. The tangled networks that direct our conscious and unconscious selves are oddly, wonderfully malleable—just like our ever-evolving ideas about the brain itself.

Poke around for more on Inkling about the surprising behavior of the brain.