Forced memory loss has been the focus of countless works of fiction — a vehicle into unpursued paths and lives not lived. Now scientists claim the practice of shock therapy may have real-world application in erasing unwanted memories, particularly as a means to rehabilitate the scars left by post-traumatic stress disorder (PTSD) and major depression.
Current theories about memory formation argue that people have a thin window of time between actually forming the memory and then storing it for later recall. It’s within that space, scientists argue, that electroconvulsive therapy (ECT), or shock therapy, may be able to interrupt the reconsolidation process, filling the memory with an implanted one or erasing it entirely. For patients whose daily lives are filled with constant mental anguish, the controversial method may have outstanding benefits.
A new study published in the journal Nature Neuroscience showed that each of the researchers’ 42 subjects responded to the therapy. In order to test their theory, which recalls the plot of Eternal Sunshine of the Spotless Mind, in which two lovers lose the memory of one another on purpose, the team showed two disturbing slideshow narratives. Afterward, they asked some of the subjects to recall one of the narratives. Then, they administered ECT. A day later, when the participants were asked to recall the same slideshow, they failed.
This signaled a time-dependent window in which memory reconsolidation occurred. Further, when they gave the same multiple choice test 90 minutes after the slideshow, both groups performed equally well. The details, then, were lost in the storage, not the immediate recall, of subjects’ memory. ECT didn’t cause memory loss; rather, it stopped long-term memories from ever forming.
"This provides very strong and compelling evidence that memories in the human brain undergo reconsolidation, and that a window of opportunity exists to treat bad memories," Daniela Schiller, a neuroscientist at Mount Sinai Hospital in New York who studies memory reconsolidation, said in a news release.
Led by Dutch researcher Marijn Kroes, a neuroscientist at Radboud University Nijmegen, the study could have deep implications for how patients with severe mental illness are treated. Though ECT has been derided as a crude, or at the very least, controversial, method of treatment, modern researchers believe its use as a last resort can have profound effects on patient well-being. Dr. Jan-otto Ottosson, a professor of psychiatry and expert on medical ethics, notes in Psychiatric Times that ECT is indeed controversial, but it is also capable of adhering to the three principles of ethical medicine: do good, do no harm, and have respect for personal autonomy and justice.
“Many randomized clinical trials crystallize the indications for ECT where its efficacy is unsurpassed by other treatments,” Dr. Ottosson wrote. “The effective indications are major depression, especially its psychotic form, and catatonia, especially its malignant form. Electroconvulsive therapy also relieves severe mania and some forms of schizophrenia. The risk of suicide decreases after ECT. In these conditions, ECT complies with the principle of beneficence.”
Kroes and his colleagues concede that ECT shouldn’t be the first line of defense in combatting depression or PTSD. In practice, it should come only after psychotherapy and anti-depressant medication have failed. “Just to be clear: It’s a long way from being an actual clinical application,” Kroes told National Geographic, adding that ECT should only be used in cases where the patient is in a “disease state.” “A lot of experimental, fundamental science is often very difficult to translate into the real world.”
Admittedly, much of this translation is difficult because memory formation is extremely complex. Nerve cells change their very structure, because of shifts in dendritic spines in the brain — small, bulb-like structures that receive electrochemical signals from other neurons. Ultimately, this process can happen thanks to a protein called actin. In a study performed earlier this year, scientists that prevented actin polymerization in mice were able to erase specific memories.
"Our memories make us who we are, but some of these memories can make life very difficult," Courtney Miller, an assistant professor at The Scripps Research Institute who led the research, said in a statement. "Not unlike in the movie Eternal Sunshine of the Spotless Mind, we're looking for strategies to selectively eliminate evidence of past experiences related to drug abuse or a traumatic event. Our study shows we can do just that in mice — wipe out deeply engrained drug-related memories without harming other memories."
So for now, Kroes explains, the process is still years in the future. But the important takeaway is that new avenues are opening up with each successive and successful study. "The ability to permanently alter these types of memories might lead to novel, better treatments," he said.
Source: Kroes M, Tendolkar I, van Wingen G. An electroconvulsive therapy procedure impairs reconsolidation of episodic memories in humans. Nature Neuroscience. 2013.