The First Human Trials of A Memory Prosthesis Look Promising

What if there was a way to artificially boost the brain’s ability to retain memories? A new study in Frontiers in Human Neuroscience provided some of the first evidence that a “Memory prosthetic” is possible in humans.

It holds that memories are simply electrical signals generated by a well-regulated neural highway inside the hippocampus. If we can capture these signals while a person is learning, then in theory we could play the recordings back to the brain-in the form of electrical zaps-and potentially boost that particular memory.

The team built on their previous work of engineering memory prosthetics. In people with epilepsy, they showed that by re-introducing neural signals encoding one type of memory in a specific task, the zaps boosted recall by over 50 percent.

Those who suffered from previous memory loss showed the best improvements. To be clear, the team did not develop a video camera for memory.

The system partially mimics the hippocampus’ normal process for memory encoding and recall, which can be notoriously subjective and somewhat unreliable.

A similar memory prosthetic might not work well in the real world, where we’re constantly bombarded with new experiences and memories.

That said, the study shows a way to help people with dementia, Alzheimer’s, or other causes of memory loss retain snippets of their lives that could otherwise be lost.

“It’s a glimpse into the future of what we might be able to do to restore memory,” said Dr. Kim Shapiro at the University of Birmingham, who was not involved in the study, to MIT Technology Review.

The hippocampus, a seahorse-shaped structure, is often described as a monolithic hub for memories. For the memory prosthetic, the team focused on two specific regions: CA1 and CA3, which form a highly interconnected neural circuit.

Decades of work in rodents, primates, and humans have pointed to this neural highway as the crux for encoding memories.

The team members, led by Drs. Dong Song from the University of Southern California and Robert Hampson at Wake Forest School of Medicine, are no strangers to memory prosthetics.

With “Memory bioengineer” Dr. Theodore Berger-who’s worked on hijacking the CA3-CA1 circuit for memory improvement for over three decades-the dream team had their first success in humans in 2015.

To crack the memory code, the team worked out two algorithms.

The first, called memory decoding model, takes an average of the electrical patterns across multiple people as they form memories.

In a series of experiments, first in rats and monkeys, then in healthy humans, the team found that their memory prosthetics could improve memory when neural circuits were temporarily disrupted, such as with drugs.

Bypassing injured circuits isn’t enough-what they wanted was a true memory prosthetic that could replace the hippocampus if damaged.

Each participant rapidly cycled through 100-150 trials, during which their hippocampal activity was recorded to capture their short-term memory.

One day between removing the electrodes, the participants underwent another round of memory tests similar to the ones before. Overall, stimulating the brains of people with epilepsy boosted memory performance by roughly 15 percent.

“Irrespective of baseline memory function, the MIMO model produces at least double the facilitation compared to the MDM model,” the team said.

While a memory prosthetic could benefit people with Alzheimer’s, lots more details need to be ironed out.

At the very least the study shows that, similar to a brain-controlled prosthetic limb, a memory chip isn’t impossible for people who need it the most.