An electrical brain-stimulation technique used to treat Parkinson's disease and chronic pain appears to enhance human memory as well, according to a tiny but intriguing new study that bolsters hope for one day developing a nondrug treatment for memory problems, including ailments like Alzheimer's disease.
The new study, published in the New England Journal of Medicine, focused on seven patients with severe epilepsy whose memory abilities ranged from normal to severely impaired. They had electrodes implanted through a hole in the skull in order to detect the source of their seizures. This gave researchers the chance to send an undetected burst of current to different brain regions, known as deep-brain stimulation, and observe changes in memory.
The participants completed a task where they pretended to be taxi drivers who needed to drop off passengers at stores on different blocks. Researchers stimulated the brains of participants when they were learning the location of half the stores but not the others. Participants were tested for how well they remembered the location of the stores.
All patients, regardless of how good their memory was, saw improvement in their memory after stimulation in a particular brain region known as the entorhinal area. Stimulating areas just millimeters away showed no benefit.
The entorhinal cortex is an area of the brain that is one of the first to be damaged by Alzheimer's. Fibers from that region transmit the sensory information to the hippocampus, a brain region critical to learning and memory. The thinking is that the stimulation enhanced learning or the encoding of memories, perhaps by resetting the electric rhythm of brain cells within the hippocampus, according to Itzhak Fried, a study author and professor of neurosurgery at the University of California, Los Angeles, and Tel Aviv University in Israel.
The work is preliminary, and extensive follow-up is needed. But, "the hope would be that this type of approach—deep-brain stimulation—can be used to help people with memory problems," Dr. Fried said.
For the field of Alzheimer's research, the finding "breaks new ground," said Stephen Salloway, an Alzheimer's researcher and professor of neurology at Brown University who wasn't involved in the current study. "It doesn't provide a definitive answer; it opens new doors to exploratory treatments for Alzheimer's," he said.
The majority of treatments in development to treat Alzheimer's and related dementias are drugs that target the protein amyloid, which clumps to form plaques in the brain and is thought to contribute to the disease.
The arrow shows where deep-brain stimulation was applied to this brain during tests on learning.
Questions remain about using deep-brain stimulation to treat dementia, including whether it would work for Alzheimer's patients and at what stage of decline, whether it is safe and how long the effect will last, said Dr. Salloway. The Food and Drug Administration has approved deep-brain stimulation to treat Parkinson's and a movement disorder known as dystonia, and it is used to treat chronic pain and severe depression.
The next step is to figure out if stimulation also can help when recalling old memories, because that function can also be impaired with dementia, according to Nanthia Suthana, the first author on the study and a UCLA postdoctoral researcher.
Unlike stimulation for treatment of Parkinson's or other issues, in which the brain is stimulated continuously or repeatedly with an implanted pacemaker-like device, memory in the latest study was improved by a single burst of current when administered in the right location as memories were being formed, according to Dr. Fried.
Recent animal studies have shown that stimulating the entorhinal cortex improved the growth of brain cells in adult mice and appeared to enhance memory for locations and spatial knowledge.
In humans, evidence has been limited. A 2010 study of six Alzheimer's patients who received continuous brain stimulation to a different part of the brain over a 12-month period suggested possible improvements in memory. And in some previous studies where the hippocampus was stimulated, memory was actually disrupted.
The notion that deep-brain stimulation may have benefits for memory was prompted in part by serendipity. In a 2008 case report, a man who was receiving experimental brain stimulation for obesity also showed improvement in his memory, which prompted excitement and calls for future research.
Could you imaging us all going around with this type of device in our heads to remember everything? Heck, in PvP we could all learn our characters and play them to perfection if we could remember every detail of every encounter!