In the study, the research team determined the precise patterns for each person’s high-functioning state, when memory storage worked well in the brain, and low-functioning mode, when it did not.
The scientists then asked the patients to memorize lists of words and later, after a distraction, to recall as many as they could.
Each participant carried out a variety of tests repeatedly, recalling different words during each test. Some lists were memorized with the brain stimulation system turned on; others were done with it turned off, for comparison.
On average, people did about 15 percent better when the implant was switched on.
“I remember doing the tests, and enjoying it,” said David Mabrey, 47, a study participant who owns an insurance agency outside of Philadelphia. “It gave me something to do while lying there.”
“But I could not honestly tell how the stimulation was affecting my memory. You don’t feel anything; you don’t know whether it’s on or off.”
The new technology presents both risks and opportunities. Dr. Kahana said the implants could potentially sharpen memory more dramatically if the approach were refined to support retrieval — digging out the memory — rather than only storage.
Still, as currently devised, the implant requires that multiple electrodes be placed in the brain to determine its high- or low-functioning state (though stimulation is sent to just one location).
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