Implanted electrodes a 'breakthrough moment' for recall
Pulses from electrodes implanted in the brain can improve memory in some individuals, according to research published in the journal Current Biology. The study by scientists at the University of Pennsylvania focused on epilepsy patients and the hope is that electrical impulses transmitted via the implants will be able to bolster memory for people with a variety of conditions, including dementia. However, the process of implanting the electrodes is technically complex and if done incorrectly can cause damage. Scientists said there needs to be more research to determine whether the treatment can be effective in other conditions.
The new study is the latest chapter in an extraordinary, decades-long collaboration among cognitive scientists, brain surgeons and people with severe epilepsy being evaluated for an operation. The preoperative “evaluation” is a fishing expedition of sorts, in which doctors sink an array of electrodes through the top of the skull and wait for a seizure to occur, to see whether it’s operable. Many of the electrodes sit in or near memory areas, and the wait can take weeks in the hospital. Cognitive scientists use this opportunity, with patients’ consent, to present memory tests and take recordings.

This approach — called direct neural recording, and piggybacking entirely on the clinical placement of the electrodes — has become the leading edge of research into the biology of human memory. This study used data from 150 patients, and had 20 collaborators from institutions around the country, including Emory University, the University of Washington, the Mayo Clinic and the University of California, San Francisco.

In a series of experiments, the researchers had patients memorize lists of words and later, after a distraction, asked them to freely recall as many of the words as they could. All the while, the scientists monitored a handful of “hot spots” in the brain which, previous work had shown, were strongly related to memory encoding. Before the stimulation tests, the team determined the precise settings for each patient’s high- and low-functioning states.

Each participant carried out the word-memorization tests repeatedly, with different words every time; some lists were memorized with brain stimulation, and other lists with no stimulation, which served as a control. The authors then examined memory performance based on whether stimulation arrived during low- compared with high-functioning brain states.