Could generating new cells in brain regions associated with memory stave off the symptoms of Alzheimer’s? A new study by researchers in Canada, who used deep brain stimulation to trigger neuron growth in mice, suggests it can.
Last year, a small safety study of deep brain stimulation (DBS) in humans found that it slowed rates of cognitive decline and even led to some actual memory improvement in six patients with early stage Alzheimer’s. These patients had the brain stimulators — electrodes implanted in a targeted area of the brain — activated for one year.
The current research in mice used DBS in the entorhinal cortex, a brain area that interacts with a critical memory region called the hippocampus. Without a functioning hippocampus, neither humans nor mice can form most types of new memories.
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Researchers found that when the brain stimulators were turned on for one hour, the growth of new brain cells in a key region of the hippocampus nearly doubled. Researchers noted the increase three to five days later and found that the effect last for a week.
Following the new brain-cell growth, the mice were tested in a water maze. The animals that received brain stimulation showed memory enhancement, more easily learning to find a hidden platform in the maze than control mice.
“It’s a really fabulous paper,” says Marco Iacoboni, professor of psychiatry at the University of California, Los Angeles, who was not associated with the research. “First it shows unequivocally that you can stimulate the brain and induce neurogenesis. Others have shown that, [but this research demonstrates] that by doing that, you actually increase performance. The mice doing a maze task actually get better after stimulation.”
Iacoboni notes that the improvement wasn’t dramatic, but says, “It’s really there.”
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But the researchers didn’t stop there. To be sure that it was the cell growth that was causing improvements in memory, and not some other effect of DBS, the researchers then used a drug to stop the growth of new cells following stimulation. That intervention precluded enhanced learning in the mice, the researchers found.
The scientists also noted that the animals’ memory improvements took about six weeks to materialize after brain-cell growth with DBS. Not coincidentally, that’s about the amount of time that it takes for new brain cells to mature and integrate into the circuitry.
It’s also probably not a coincidence that it typically takes about the same amount of time for the effects of antidepressants to kick in fully; previous research has linked antidepressant action to the growth of new brain cells in the hippocampus. Another depression treatment, electroconvulsive therapy (ECT), also uses electrical stimulation — perhaps new brain cell growth could help explain why ECT works.
Currently, DBS is used mostly in patients with Parkinson’s disease, which causes movement problems like tremors and difficulties starting, stopping and coordinating movement. DBS in the relevant areas of the brain has allowed patients to “move like young men again,” says Iacoboni.
More than 60,000 patients with Parkinson’s, along with those with treatment-resistant cases of depression and severe obsessive-compulsive disorder, have been treated with DBS. Could it help some of the 5 million Americans — 13% of the population over 65 — living with Alzheimer’s?
It’s obviously an invasive, expensive therapy, and carries the significant risks of any type of brain surgery. But as anyone who has watched a loved one dissolve into the void of dementia knows, even an invasive treatment that may actually stave off the loss of self and help preserve everyday function would be an incredible advance.
The new study was published in the Journal of Neuroscience.
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