Using a 30-year-old brain stimulation technique, scientists have successfully boosted memory performance in healthy adults by zapping a specific bunch of neurons. While it’s unclear at this stage whether the effects will be long-lasting, the researchers are hopeful it could one day be used to treat patients with conditions that affect memory, such as Alzheimer’s. The study has been published in Science.
Brain zapping might sound horrifying, but transcranial magnetic stimulation (TMS) is a non-invasive procedure that’s been studied as a potential treatment for various disorders since the 1990s. TMS involves using magnets that are carefully positioned on the scalp to induce weak electric fields; these transient fields then stimulate nearby neurons in the outer layer of the brain called the cortex. Although researchers aren’t exactly sure why it works, it does appear to have positive effects on some patients with depression. The possibility that this technique could affect neuronal circuits involved in memory, however, had not been previously investigated.
To find out more, a team of neuroscientists based at Northwestern University enrolled 16 healthy participants between the ages of 21 and 40. The team first used MRI scans to map their brains, locating a region called the hippocampus that is known to be critical for learning and memory. They also identified another region called the lateral parietal cortex that is strongly synchronized with the hippocampus.
Previous studies have shown that activity between these two regions increases while individuals are performing memory tasks. Given that TMS is unable to reach deep brain structures such as the hippocampus, the researchers stimulated the parietal cortex in the volunteers.
The team began by examining the participants’ memory using a variety of tests and then splitting them into two groups: one group received sham TMS, whereas the other received the real thing. They administered the treatments for 20 minutes per day for 5 days and then repeated the memory tests and brain scans. They found that, on average, those who received TMS improved their scores by around 30%. Furthermore, they found that TMS significantly increased the communication between the hippocampus and several other areas, including the parietal cortex.
To make their study even more robust, the researchers also stimulated some control regions that are not heavily synchronized with the hippocampus, such as the motor cortex. They found that stimulating this region did not significantly affect either hippocampal connectivity or memory test scores. It did make the participants do some weird things, though, such as twitching and involuntarily raising one arm.
This study is exciting because it not only shows that the hippocampus can be successfully stimulated indirectly, but it also demonstrates the importance of other brain regions in memory which may have been previously downplayed.
While the results are certainly encouraging, at this stage it is not clear whether the effects are long-term, or if only specific types of memories are affected by the procedure. Furthermore, it is too early to tell whether this could be an effective treatment for memory loss. However, the team are due to initiate a trial in which they will investigate TMS on patients with early-stage memory loss, which may yield some answers.
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