Courtesy of Massachusetts General Hospital and Draper Labs
Like so many other things in the realm of brain technology, Deep Brain Stimulation (DBS) sounds like a procedure straight out of a sci-fi movie. But just like most of these technologies, DBS is as real as it gets. The idea is rather simple: insert electrodes into parts of a person’s brain, and deliver small electric shocks with the purpose of improving symptoms of a given disease.
When it started being practiced as a form of nonsurgical treatment, DBS was mainly used to treat symptoms of Parkinson’s disease (PD) and other motions disorders. By implanting electrodes in the thalamus, globus pallidus, or subthalamic nucleus, and delivering small electric shocks, debilitating symptoms like tremor, involuntary movements, rigidity, walking problems, etc, can be reduced. One positive feature of DBS is that it involves minimal surgical changes to the brain. Moreover, while treatment may lead to unwanted side effects, these can be dealt with by removing the electrodes along with the pulse generator placed under the collarbone.
By now, a number of other disease symptoms are targeted using DBS, although in some of these cases, the use of DBS is still in the experimental phase. For instance, DBS has shown potential to help up to 20% of those who suffer from refractory depression, i.e. depression that is unresponsive to any kind of treatment. It has also been shown to help those with severe OCD, as well as chronic pain.
But perhaps the most interesting domain in which DBS has been shown to have an effect is memory. The research is rather new, and only a handful of studies have demonstrated the effects of DBS on memory improvement. In a 2012 study published in The New England Journal of Medicine, Suthana and colleagues used DBS to stimulate the hippocampus and entorhinal cortex, which are important structures for transforming daily experience into lasting memories. They took 7 patients with epilepsy, who completed a spatial learning task in which they had to navigate a virtual environment to deliver passengers to stores. The subjects had a total of six routes to learn, and DBS was applied during three of these routes. The authors found that, when learning was coupled with DBS, subjects showed improved memory performance compared to without DBS.
In yet another study published in Brain, Miller and colleagues (2015) showed that DBS of the fornix can improve visual-spatial memory. Previous research on rodents has shown that DBS of the fornix can improve memory after brain injury. The researchers had epilepsy patients complete three memory tasks. When DBS was applied, subjects showed memory improvement compared to when DBS was not applied.
So what are the practical implications of the effects of DBS on memory? Apart from the obvious future possibility of using DBS to improve visual-spatial memory—I can think of getting DBS-ed while studying for an exam, but I don’t want to go too far into the realm of speculation—its most effective use will likely be found in the treatment of Alzheimer’s disease. Given that memory loss is a paramount symptom of the disease, the use of DBS on parts of the brain that process memory may help improve symptoms.
In fact, a number of studies have shown positive effects of DBS on Alzheimer’s. One study showed that the volume of the hippocampus (important for memory) increases with DBS stimulation in Alzheimer’s patients, suggesting that this may be accompanied with memory improvements. Perhaps most importantly, Dr. Lozano and colleagues at Toronto Western Hospital have shown that DBS may slow the progression of the disease.
In the future, DBS may well become a crucial component in the treatment of Alzheimer’s, as well as other conditions that include memory loss. This should come as good news to those who are anxious about the effects of aging. Who knows—DBS might soon be a game-changer for the treatment of all sorts of conditions.
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