Brain implants could soon help prevent memory loss

Memory loss can soon be prevented by the use of brain stimulation through implanted electrodes. Tests funded by the US military are underway and initial evidence suggests that such devices can help retain memories.

The electrodes work by mimicking electrical patterns that create and store memories. Such neuroprosthetics can help not only those affected by brain injuries and strokes, but also the elderly.

Two teams funded by the Defense Advanced Research Projects Agency, have begun work by recording and stimulating brain activity in epileptics, who already have implants in their brains.

Short-term memory stored in the hippocampus is translated into long-term memory if it is accessed during a brief period since storage. The brain process behind this involves a signal being sent from one region of the hippocampus CA3 to another called the CA1.

Recreating this signal in people with damaged hippocampus may help restore memory, believes biological engineer Theodore Berger at the University of Southern California (USC) in Los Angeles.
By recording the patterns in epileptics, they developed an algorithm to predict CA3 pattern based on what was recorded at CA1 cells. The algorithm was 80% accurate.

They hope to stimulate CA1 cells even when the CA3 is damaged. It has been tried on one woman, but will require more time to know the results. The team wants to try stimulating more people in the coming days.

Memory mimicking could, however, be difficult if the CA1 cells are badly damaged. Since the hippocampus receives inputs from many connections in the brain, some experts think stimulating it with the CA3 signal alone may not be enough.

Mechanism not clear

Another team at the University of Pennsylvania (Penn) in Philadelphia has discovered that stimulating a region called the medial temporal lobe, which houses the hippocampus, was enough to revive fading memories. But stimulating a healthy individual actually worsened memory.

They developed their algorithm after recording brain activity in 28 people, and used it to predict accurately, the memory responses in others when stimulated. In cases where a person read words that were likely to be forgotten, the researchers could boost performance by up to 140%.

Both methods, however, do not explain how the memory is recovered and why stimulating some regions helps.