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Personal Brain Stimulation Shown to Boost Memory

Brain circuits illustration

(HypnoArt, Pixabay)

7 February 2018. A team of psychologists and neuroscientists developed techniques for monitoring and electrically stimulating key parts of the brain, personalized to each individual, which in tests show can improve a person’s memory. A description of the techniques and results of the tests appear in yesterday’s issue of the journal Nature Communications.

Researchers from the Computational Memory Lab at University of Pennsylvania in Philadelphia, led by the lab’s director and psychology professor Michael Kahana, are seeking to make electronic brain stimulation a more consistent and reliable technology for improving human memory. In earlier studies, the team found electrical stimulation alone could not produce consistent outcomes, with the results, including beneficial outcomes, often unrelated to the electrical pulses.

In addition, Kahana and colleagues questioned the usual targets of stimulation, namely the hippocampus and medial temporal lobe most associated with memory formation. Stimulating those regions often returns mixed results in enhancing memory functions, say the authors, and in their review of recent experimental research, identified a part of the lateral temporal lobe as a promising target. This part of the brain is associated with processing semantic memories: knowledge of objects, people, words, and facts.

The project, funded by the Defense Advanced Research Projects Agency, or Darpa, under its Restoring Active Memory program, had two objectives, as described by postdoctoral researcher and first author Youssef Ezzyat. “We developed a system to monitor brain activity and trigger stimulation responsively based on the subject’s brain activity,” says Ezzyat in a UPenn statement. “We also identified a novel target for applying stimulation, the left lateral temporal cortex.”

To monitor brain activity and apply the electrical stimulation, the researchers implanted electrodes into the left lateral temporal cortex and other regions of 25 patients at several cooperating hospitals already undergoing electroencephalographic or EEG monitoring inside the brain to help treat drug-resistant epilepsy. The participants performed free-recall memory tasks in 3 sessions of 45 minutes each to discover their individual brain activity patterns. These exercises helped construct personalized brain activity computer models, making it possible to tailor electrical stimulation for each individual.

Participants then performed new memory exercises using word lists, with the implanted sensors recording the individual’s brain signals and responding as needed with mild electrical impulses, not detected by the participants. “During each new word the patient viewed,” notes Ezzyat, “the system would record and analyze brain activity to predict whether the patient had learned it effectively. When the system detected ineffective learning, that triggered stimulation, closing the loop.”

The results show participants are more likely to remember words learned during the stimulation periods than in similar exercises where no stimulation is applied. In addition, words presented immediately before or after stimulation, are also more likely to be remembered, even if no stimulation is given at those precise moments. And words presented during stimulation of the left lateral temporal cortex are also more likely to be remembered than when stimulating other parts of the brain.

“Now we know more precisely,” says co-lab director Daniel Rizzuto, a co-author of the paper, “where to stimulate the brain to enhance memory in patients with memory disorders, as well as when to stimulate to maximize the effect.” Rizzuto is forming a new company, Nia Therapeutics LLC, to develop  neurostimulation therapies to treat memory impairment, based on the lab’s research. He is now the company’s CEO.

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