A Memory Prosthesis Can Restore Memory in Individuals with Damaged Brains

Brain electrodes developed to mimic the hippocampus appear to increase the encoding of memories– and are two times as effective in people with bad memory.

A singular form of brain stimulation seems to boost people’s capability to remember new details– by imitating how our brains create memories.

Memory prosthesis

The “memory prosthesis,” which includes putting an electrode deep into the brain, also appears to work in individuals with memory disorders– and is even more effective in people who had a poor memory, to begin with, according to a new study. In the future, forward versions of the memory prosthesis could assist individuals with amnesia due to brain injuries or as an outcome of aging or degenerative illness like Alzheimer’s, state the scientists behind the work.

“It is a glimpse into the future of what we could be capable to perform to restore memory,” states Kim Shapiro, a neuroscientist at the College of Birmingham in the UK, who was not associated with the research.

It works by replicating what occurs in the hippocampus– a seahorse-shaped area deep in the brain that plays an essential function in memory. The brain framework not just assists us in forming temporary memories but likewise appears to direct memories to other areas for lasting storage.

Imitating memory

Theodore Berger and Dong Song at the College of Southern California and their associates have been developing a way to imitate this process for over a decade. Their concept is to utilize brain electrodes to understand the electric patterns of activity that happen when memories are encoded. After that, they utilize those same electrodes to fire identical activity patterns.

The group has examined versions of this prosthesis in creatures and in some human volunteers with epilepsy who currently had electrodes implanted in their brains to much better comprehend and solve their condition.

To discover if it might assist people with bad memory, Rob Hampson, a neuroscientist at Wake Forest College School of Medicine in North Carolina, and his associates examined two versions of the memory prosthesis in 24 individuals who had implanted electrodes to study their epilepsy, several of whom also had brain injuries.

The first version

The initial version, which the group names a memory decoding version (MDM), imitates patterns of electric tasks across the hippocampus that happen naturally when each voluntary effectively forms memories. The MDM design takes an average of these patterns across each person and, after that, fires off this pattern of electric stimulation.

The second version

The second kind, called multi-input, multi-output (or MIMO), more closely imitates how the hippocampus functions. In a healthy hippocampus, electric activity flows from one layer to another prior to spreading to other brain areas. The MIMO design is based upon learning the patterns of electric inputs and also outputs that correspond with memory encoding and then imitating them.

Unique Brains

Hampson and his associates asked the volunteers to take part in memory examinations to examine how well each of the models functions. In the analyses, everyone was shown an image on a computer display. After a delay, the same image was shown once more, together with a selection of others. The person had to select which was the picture that had already been shown. Each volunteer finished around 100 to 150 of these brief tasks, which are designed to examine an individual’s temporary memory.

In between 15 and 90 mins later, each person went through a 2nd examination– this time being shown a set of three pictures and asked to choose which was most familiar. This test shows an individual’s long-term memory.

The volunteers took on both rounds of memory tests two times– once to record from the hippocampus and once to boost those recorded patterns associated with successfully stored memories. The recordings were single, states Hampson: “So far, we find that it’s distinct for each individual.”

The group found that its memory prosthesis enhanced the volunteers’ performances on memory examinations– their scores were considerably greater if they had received the appropriate pattern of stimulation when initially presented with the images. This suggests that the memory prosthesis can assist encode memories in brain, the researchers state. “We’re seeing developments that range from 11% to 54%,” states Hampson.

Personalizing brain

Personalizing brain stimulation in this manner is “a truly important thing to be performing,” states Josh Jacobs at Columbia University, that likewise studies brain recordings from individuals with epilepsy but was not involved in the current study. Up until now, doctors and researchers have had some success in treating disorders like Parkinson’s illness by just targeting the similar brain area in all individuals.

“But individuals have really distinct brain reactions,” states Jacobs. Customizing stimulation to particular brains is likely to enhance its effect, he states.

The MIMO design, which more nearly mirrors how the hippocampus functions, had even better outcomes, on average. And also, the greatest enhancements were seen in people who had the worst memory efficiency at the beginning of the experiment. The scientists are not sure why this is; however, maybe  because there is “more room for progress,” states Hampson.

All the voluntaries had their electrodes removed within a couple of weeks once their doctors had finished examinations into their epilepsy. But Song hopes the enhancements to their memories will be lasting. In theory, each person’s stimulation might have strengthened the wiring of neurons in the hippocampus; he states: “We don’t actually understand; however, we wishes so.”

Restoring memory

Song, Hampson, and their associates, who released their discoveries in the journal Frontiers in Human Neuroscience in July, hope their memory prosthesis might someday be widely used to restore memory in individuals with memory disorders.

“Brain injury patients would be the first [candidates],” states Song. Such injuries have a tendency to affect particular regions of the brain. Injuries to the hippocampus would be simpler to target than degenerative illnesses like Alzheimer’s, which have the tendency to involve damage across many areas of the brain.

“It seems feasible to me that one day we could change a hippocampus with something else,” states Jacobs. But he points out that it will be hard to completely replicate a healthy hippocampus– the structure contains 10s of numerous neurons. “It is a little difficult to imagine how a handful of electrodes could be replacing the millions of neurons in the hippocampus,” he states.

The electrodes utilized in the study are around a millimeter wide, and all the volunteers had them implanted deep sufficient into the brain to get to the hippocampus– around 10 centimeters deep. They are fairly crude by contemporary research standards and can record from about 40 to 100 neurons, states Song. Any memory prosthesis designed to treat memory problems will need mind electrodes with hundreds of contact points, enabling them to record from and also stimulate hundreds or thousands of neurons, he states.

Hampson, Song, and their coworkers have not yet worked out how the memory prosthesis may operate in practice. It may not make sense to have the tool running all the time, for example– there are plenty of life experiences, like taking out the garbage, that people with memory problems don’t require to keep in mind. “Why waste the [brain] space?” Jacobs states.

The memory prosthesis is still far from clinical use, but in development

Song believes the prosthesis may be utilized alongside some kind of device that can tell whether the device requires to be running or not– maybe by spotting when the brain requires to be in a ready-to-learn state.

And also, Song doesn’t yet understand if a memory prosthesis should run overnight, either. It is thought that when we rest, the hippocampus replays some of the memories encoded throughout the day to consolidate them in other brain areas. Song and his coworkers do not know if a memory prosthesis that copies this replay would get the memory better or whether it’s a good idea to boost the hippocampus at all while an individual is sleeping.

Either way, the prosthesis is still some way from clinical usage, states Shapiro. “I think, in principle, it might function,” he says.” [But] we have a long way to go before we comprehend sufficient regarding memory to be capable to utilize this kind of method to replace hippocampal function.”

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