Electroconvulsive therapy has a public relations problem. The treatment, which sends electric currents through the brain to induce a brief seizure, has barbaric, inhumane connotations — for example, it was portrayed as a sadistic punishment in the film One Flew Over the Cuckoo’s Nest. But for patients with depression that does not improve with medications, electroconvulsive therapy (ECT) can be highly effective.
Studies have found that some 50% to 70% of patients with major depressive disorder see their symptoms improve after a course of ECT. In comparison, medications aimed at altering brain chemistry help only 10% to 40% of depression patients.
Still, even after many decades of use, scientists don’t know how ECT alters the brain’s underlying biology. Bradley Voytek, a neuroscientist at the University of California, San Diego, said a psychiatrist once told him that the therapy “reboots the brain” — an explanation he found “really unsatisfying.”
Recently, Voytek and his collaborators paired their research into the brain’s electrical patterns with patient data to explore why inducing seizures has antidepressant effects. In two studies published last fall, the researchers observed that ECT and a related seizure therapy increased the unstructured background noise hiding behind well-defined brain waves. Neuroscientists call this background noise “aperiodic activity.”
The authors suggested that induced seizures might help restore the brain’s balance of excitation and inhibition, which could have an overall antidepressant effect.
“Every time that I talk to someone who’s not in this field about this work they’re like, ‘They still do that? They still use electroshock? I thought that was just in horror movies,’” said Sydney Smith, a graduate student in neuroscience in Voytek’s lab and the first author of the new studies. “Dealing with the stigma around it has become even more of a motivation to figure out how it works.”
About eight years ago, Voytek teamed up with the psychiatrist Maryam Soltani, also at the University of California, San Diego, and her colleagues, who were collecting electroencephalogram data on patients undergoing ECT for diagnosed major depressive disorder. The researchers attached electrodes to the front of the patients’ heads to measure the brain’s electrical output before and after ECT treatment.
Decades of electroencephalogram studies have shown that a healthy brain’s electrical output produces patterns of repetitive oscillations, or brain waves. For example, alpha waves, with frequencies of 8 to 12 hertz, tend to appear during deep relaxation or sleep. Previous research that connected alpha waves with depression led Soltani and Voytek to initially hypothesize that ECT influences alpha waves. If true, that would also help explain why ECT tends to slow certain frequencies in the electroencephalogram output.
But a preliminary analysis of the first two patients showed something different: a marked increase in aperiodic activity or “background noise” coming from the brain.